Hi In a previous mailbag video, I showed this Hasso scope, oscilloscope schematic and how it was an example of probably one of the worst formatted schematics I've ever seen and I mentioned that this could be a good example to show how to layout a schematic properly. You know some good design techniques, industry conventions you know, rules of thumb to follow, and just some good habits when laying out a schematic. so a lot of people actually said yeah I'd love to see that. So here we go.

and I think in this particular case, it's probably better to start out with a badly formatted schematic, not only to show you what the good schematic layout techniques are and good practices are, but to show you what's bad and what doesn't work and why I think that's just as important as showing you the good technique. So I think this is a really good baseline that we're gonna use here to just tidy this up. So I'm gonna show you how to turn this higgledy-piggledy move dogs breakfast mess into this nice schematic here. stick around.

could take a while though. Now here's the original wire PDF schematic which I'll link to the github down below for the Hasso scope and I think we'll start out by just going through some of the you can already see some of the bad things that are going on here. so I thought we'd do a video tidying this up, completely tidying this up from scratch. Now unfortunately this was done in Eagle I don't know how to use Eagle and I don't really want to learn how to use the Eagle schematic editor just to do this video.

So what I've done is I've actually imported this into out Iam designer and you can see that it's some practically identical. It's got all the same issues. There's a few differences, like for example, take these like nets. you know, a few font, rotational things and stuff like that.

If we compare that with this over here, you can see it's it's like you know it's actually a bit tie already in Altium Designer than it is. Look at these like they're backwards and they're those labels. Therefore, the JTAG they're all backwards and over this and and it's just like it's terrible. Muriel So anyway, but it's pretty darn close to the original PDF The Altium import Eagle import actually did very well.

so we're basically starting off with the same framework. It's just going to be easier for me to use Artyom, which I'm familiar with to do this. So let's go. Let's first look at some of the bad things that you shouldn't do in schematic layout.

and by the way, I'm recording this in 2k so if you want to watch it in its native resolutions, that's just this screen that I'm using. It's a bit harder to capture in 1080p. it's just a smaller working window. So first of all, what I'm actually going to do is I've got the original version of the schematic and I've got the new tidy version which I haven't done anything to yet and we can actually show differences.

We can actually compare the differences between these two schematics so we can do that and when should tell us that there's no differences. So at the end of this, the idea is to keep all the Nets the same because the first rule of schematic layout is that everything must be electrically connected properly. For example, let's just go in here now. of course, a good schematic tool.

You've got to set your snap grid and of course, a good schematic tool will actually snap to the hotspot of the pin. You can probably see that big X on there for that pin. it's you know we can I think it's changed all the defaults in out here I'm not going to muck around but it will actually snap and if that's not electrically connected, if you don't set the snap grid properly, you can be like point 1 millimeters off that or something like that and it's not going to make electrical connection and then that is not gonna generator correct netlist which then it goes into your which then exports into your PCB or imports into your PCB so that you can then do design rule checking and using an electronic CAD package like this. For schematic and PCB design, it's all about electrical rules checking so that's the first thing you're going to want to do when laying out your schematics Set your snap grids now.

Unfortunately, this one is, or because it's imported, that's all off the grid. It's not something that we would have done from scratch, it to be much tidier, you can. Actually, you should be able to see the net in there as we actually do this and like it's just a lot of it's. not going to line up like it would on a normal grid design from scratch, so just be aware of that.

But snap grids are the number one thing. and electrical connections and snap into the correct pins and connections to generate your netlist is the most important thing in laying out a schematic. That's before we get to the visual part of it. Now we're going to talk about the first convention in schematic layout, and this particular design in in this case, a four channel oscilloscope is a decent example of this.

Because we're going to have analog signals coming in and then we're gonna have like digital signals coming out. It's an ADC Basically, so the first convention is schematic layout. Now, you don't have to do this, but it's kind of expected in the industry and if you don't do it, it shows that you're not a professional design engineer and you don't know what you're doing. Signals always flow, sure should flow by convention from left, over to right.

You've got to do it back to front on the camera here, left to right, so it's got to start on the left hand side here. and and so signals. If you've got signals flowing into whatever project it is, they should be on the left hand side and then they should be processed to go through amplifiers, do whatever, and then slowly work their way over to the right-hand side here. Now, because this isn't a four channel oscilloscope.

Where's our BNC s If I looked at this? If I came to a schematic. Oh, this is the schematic for an oscilloscope. Great. I'm looking for the BNC s.

Where should they be? They should be over here on the left hand side, but they're not. We've got the power supply over here. We've got an oscillator. We've got a JTAG header.

We've got some other things. Where are the BNC s? Well, they're actually hard to find. They're buried away in here. Yeah, so there's just so many things wrong with this.

Not only are they incorrectly placed on the schematic for correct signal flow across your schematic, but they're also rotated incorrectly. Looked like good. Gotta go that. to look at the look at the B and C's It's absolutely ridiculous.

And look, the grounds are upside down. For starters, that's next thing. Your ground should always be going down. Now the next ruler schematic design.

Look at the lines on here this instantly. When you immediately see the schematic, you scope what's going on these lines. I Like these ones are ok, they're going down like this. That's fine.

Lines should never be. As a general rule, never be on an angle In a schematic. they're up and down. left, right.

That's it. Okay, so it's by having the lines come down like this is is just like you would think. like, why why would anyone do that? It's absolutely ridiculous. And not only that, but look at the look at the nets here.

The nets are just like he can't tell which ones what. It's absolutely ridiculous. And no, this is not an import issue. This is in the original schematic and not only the original PDF schematic.

it's in the original Eagle file as well. So I don't know what? Look, Look at this going down like that. Like there's just no reason for that to be a thing. Now the next thing is.

never, Ever have lines going through your chip symbols like this. Look, We've got the FPGA and there's lines going through it. Never, ever do this. It.

that is just insanity. And I've got the same thing down here. Look at this. Look.

This is our chip, right? This is an Op-amp You can't even tell it's an Op-amp to start with. And well, that might be okay. Some people like to use the Op-amp Simple. Some people prefer to use the chip.

You know the actual physical chip symbol and that's fine. There's no real convention there. it's up to the individual designer to do that. but never, ever have your lines going through your chip like that.

It just makes absolutely no sense whatsoever. Now in the case of as I just said the the chip layout versus the functional Op-amp symbol, the Op-amp symbol is going to be easier to understand because you would have to go up and go look up the max forty four One six to know that it's an Op-amp To start with, you can probably get an idea from the net labels and you know the pin labels and stuff like that, what it is, but you know it's better to do it as an Op-amp symbol. But if you wanna do it as a chip, that's okay. but it just it's not as easy to read and this guy's look offered textures like the text is upside down like being the annotation for the symbol.

So this is not an important issue. This is the original schematic. Goes without saying they should be the right way up. Now here's a small thing, but once again, you've got the ground up the top.

that makes absolutely no sense You: If you're going to have these leads laid out in this configuration, this horizontal configuration like this, flip it over so that the ground is on the bottom. Now that being said, having vertical like these leads like this in a horizontal configuration doesn't make sense. So what I would do is actually rotate all these so that they're vertical so that you don't have to tilt your head like that to read the annotations. And of course, it goes without saying why is this zigzag in here like this? But you know, well tidy that up.

But it just makes more sense to put that in a vertical configuration so that you can just read all the text without having to go like that. Unless there's some physical reason, because a lot of people like to match this schematic physically with their PCB. So if the LEDs are on the PCB and a horizontal configuration, people might want to, you know a designer might want to keep it on the schematic as a horizontal configuration. And that's okay.

that's why. Also, some people are prefer to have their chip pin outs like this. They prefer to have their pin outs in the physical order of the chip so one, two three, four, five, six, seven, eight so that when you troubleshooting your board, it's easier to map the pins to on the schematic to the physical chip. And as I said, that has pros and cons are both ways.

It's better for troubleshooting to lay it out like that. but understanding the schematic, it's better to have the actual wire circuit symbol in there. in this case, the Op-amp symbol like that. And you know there may be a similar sort of things for the leads, but I would definitely put that vertically.

Just rotate selection like this. Boom see, that's just going to be much easier than we dragged out throughout the night. It's yeah, because this is an import and nothing's aligned to the grid. It's all pretty horrible.

Anyway, we want to move our ground. You'd move that down to the bottom there, and it's already. It's going to be much more readable. We need to flip around the orientation of the designators here like this, but as you can see, that's just much much nicer.

Now, speaking of which, how do you do the designators? In this case, you have a designator like this and you have a value for in this case, a resistor like this. Some people prefer to put them either side like that, and it depends on how you've got them laid out. Others prefer to have it like all up on one side. for example.

Once again, there is no convention. As long as it's consistent, you don't want to mix it up higgledy-piggledy in your schematic. So if you're gonna do it, you know it's probably okay to do it like that. we need to change our snap grid there.

so with that, we can get in there. But that's you know. In this case, it's probably okay to do it like that I'd say because there's enough space between the components. But if you want to all put them on one side on the top or on one side on the bottom, just be consistent over your schematic.

That's all. But you, sometimes you just are forced to mix and match because your schematic in one part might be like denser layout. For example, you just want to fit it all in whereas it might be more sparsely laid out in another part. And in this particular case, we've got for an oscilloscope like this: I Would this is a relatively simple schematic? Okay, I would want everything on the one page and start the flame war.

Now against those who prefer everything to be on one page if possible, or whether or not out. You were a big proponent of having things on separate pages because this is all about modular design, for example. So you might have just the processor on one page. you might have just the power supplies.

another sheet or another sheet is the industry term. Instead of that page and another sheet there, then you might have all your iOS on another sheet. Yeah, let's not get in the flame wire for an oscilloscope like this. I Love to have everything on one sheet, but sometimes it doesn't print out.

Unlike an A4 sheet. it's too small. you can't read it. and hey, granted, I don't like that either, but you know, so pros and cons of both ways.

I'm not going to get into that argument. So here we go: I'm just gonna go in there and override the snap grid a little bit and tidy it up. See, So that's nice and neat. You keep your designators nice there, you know and you want to go in there and fuss and get them all you know, right? and you wanna? This is where your snap grid comes in.

You know if if this one's it's like over here like this and this one's sort of over here like this. It's just not gonna look great when it's all lined up. You want everything lined up and perfect symmetry is a good thing in schematic layout, trust me. So but once again, this is not the best example because we haven't laid it out on the proper setup grid from the start.

I don't want to I can like change all these parts so that they move them all of the snap grid, but then that can screw up the netlist and I don't want to do that so it's not the perfect example And once again, look, unfortunately, these are not evenly spaced out. See the differences. This has a larger gap between it here here here. all that sort of stuff.

If we're laying out from scratch it, they'd all be consistently spaced and everything would be perfect. So I can actually go in here and align to grid like this and it will put everything on the grid. Now it's gonna snap because when I actually rotated all that stuff like nothing lined up. So in this particular case, we're good to go.

and now we can actually draw our line open at the end of that. Look at that. the electrical hot spot there didn't quiet isn't gonna meet. Oh, look at that.

look at that. Once again, this wouldn't happen if you had proper drawn schematics from the get-go in the package. So a few of these quirks are specific because we've imported the thing here. so sorry about that.

And that's the other thing to do with snack. When you're actually creating components, you don't want to set the center of your component to the graphical center, Always set your pins when you're laying out a new component to the snap grader. And now here's the eternal argument: Do you show the footprints In this particular case? Here we go. It's the footprint for this particular lead.

Generally, you do not show that information on your schematic. It's just clutter. so you want to go in there and you want to hide that particular item. And yeah, in some cases it can be valuable to have that on your schematic.

But for the case of a lead like this and resistors and other stuff now, it makes absolutely no sense to have that sort of stuff visible. Now, the next thing we want to do is in terms of nets. Now, when you've got like, you know, data buses coming off like this, you generally don't want to have data buses running right across your schematic some cases. and sometimes it's good.

Like, if you've got, say this chip here with these lines here and they're connected over this chip, you might just draw them straight across like that if you got your two chips side-by-side That's okay. but in this particular case if you've got here, it is d0 I Write all this sort of stuff going over to your FPGA over here. you generally don't want to be running snaking all of your traces across. Now a good program like Altium Designer will have like a buses for example and you can have them go into the buses and people like drawing then a big thick bus which then goes over so you were just really thick bus line so it goes in and that can look very nice and very professional.

We don't necessarily have to do that in this particular case. It's nice because you could show that this particular bus like you have to hunt around Wendy zero A Well where does that go? you've got to look around you chip D Zero A I don't know, Is it down here? Is it over here? It like where is it right where As if you had it, as if you drew that as a bus, you could physically draw the bus going up there and around now. I'm not going to go to the effort to draw the buses here, but by all means do that. It's a very nice very professional shows where the signals go to without having to run like eight or sixteen lines all the way around your schematic.

Now the next thing is how you line them up. This is actually done perfectly. It's already done for us. You have a little bit, you have a little bit of lying going out here, and then you have the net name on top.

You always put them on top by convention and they're all nicely lined up. Look at that. That's beautiful. Why couldn't they have done that over here? What's going on here and what are these ones here just flapping around in the breeze? I Don't understand.

Don't have stuff flapping around in the breeze. This thing should be all the way over here. They should wear. didn't like me doing that.

did it. These should be all the way over here like this and then that should be there like that. and they should be all consistent on your chips just like on this side here. So I will just tidy all those up there like that.

I've got a few little issues to sit down here. Once again, it's because we didn't lay this out from scratch. It's really rather annoying and like, what's this upside down? Give me a break. Come on.

Seriously like and what? You don't use a net like that for three 3v3 like you've mixed port's electrical ports like this with Nets Like that. Don't do that. Have it actually going up to the actual port like this so you would Have that connected over to there like that didn't automatically junction up, you wear of that. So in this particular case, this is like really messy.

Let's put it like that, then let's let let's have our ground connection over here. Okay, we can kill that ground connection like that and I don't you know you could? You could could do this several ways, but basically we're connecting that up. That's not great because we're off the grid. but and then you could have this connected over to here like this.

No problem. let's put in two junctions. The other thing is, why have we got these bypass caps just flapping around in the breeze over here? what they associated with right? Put it next. if you gonna have the bypass chip like have the bypass cap on the actual pin like this.

and in this particular case, by the way, you've got this like it's just untidy to have this line running down to ground like that. If you're going to do that, edit your part because this part is does not have the proper physical penal order. so you would go in there and modify your pin so that this pin this o'clock - pin I Know it's nice to keep them together like this, but you would keep them together so you'd move clock positive and clock negative down to here this empty space down here and then because this is just going off to a net clock positive then you could have clock negative going down to the ground. and you don't have to have this wire going all the way up there.

just avoid crossing wires if at all possible. Now in this particular case, let's have a look where this net that's just flapping around in the breeze. Let's have a look at where that's going nowhere. What? I Adore our clock.

Dora The Explora clock is going nowhere I I Don't understand what's going on there and that's another thing. Like if you're not, there's no point labeling nets if they're not going to go anywhere, so we should just kill those and there's just like there's simply no point having those. Maybe if you want to give them like the names already in there so actually call it, calling them the same thing over here and then have E if they're not electrically going anywhere, don't label them at all, just physically don't connect them and again, this is crazy. You got the ground point.

not on is the ground symbol upside down, but it's actually on the upper side. And like follow some consistency here. So if you got to have this cap like put it next to this cap here, have this coming out like this like it's not rocket science and then you can join those two traces like that and have the one ground symbol like that. It's much nicer and in this case here these are nets going off.

Presumably they go off where else. It's no. I was gonna say these Nets go off somewhere else, but they don't But if they did, you wouldn't put the net just on there like this. What you would do is move it out like this right and then have them coming out because it signifies that the signal is coming out like that.

Okay, so that's just nicer up. It's okay, it's not the best cuz we're off the grid. but you get the idea. Okay, you have them going off like that.

so it signifies that the signals are either coming in or going out. And yeah, you just don't have them like lying in the middle of the net like that. actually have an extender line coming out and put the nets on the end of the line. And personally, I find this part a bit messy.

Here's all the VCC pins. Okay, you've grouped your different decoupling capacitors together. That's nice. You want to do that if the three decoupling capacitors in this case the you know.

it's not uncommon to have a ten, Michael one, Mike and a point one. Mike For example, to get the different impedances I've done a whole video on why you should put why you'd put multiple bypass capacitors in parallel near a chip. Anyway, it's a bit messy having this line running off here. I would simply have the VC like I'd have this physically near it.

so I'd actually get rid of that line there. and I just add a extra net down here like this, right? Just put the extra net on there like that and just have, then just have all this like physically close to the chip. like that. It's just.

it's just nicer. Minimize the lines running across your sheet or in this particular case, I Would you know? you could argue that? Well, you could you know. Move this down, move this up and put the capacitors and physically extend the line across here. and then just run the capacitors down like that.

But either way, works. You just wanted to get rid of that little line. little dagi line in there and likewise down here. Like just like optimise space.

This is just like too far away from these pins over here. Just just move it closer. Do yourself a favor. There you go that looks nicer and we can, you know, tidy that up once we don't need that visible and once again, weather it when you've got two capacitors like this.

Whether or not you put the ground and Veet Some people like to put it in the middle like that and then split off to the two capacitors. Others like to have it off to one side like this. for example. they prefer to have it like that and like that for exam.

in. once again, it's the grid. Either way, it doesn't matter, just put it physically close and neat and tidy. Once again.

power on the top, ground on the bottom, near the pins that you're actually decoupling. And just a small thing here. Don't have this line like this. You know, like keep some consistency.

Well, keep some consistency. like that it's not gonna snap. but you know what I mean. And of course this connector.

here. we're gonna have to do something about this. Not only is it all upside down, but it's kind of got the lines running through the connector. There's everything wrong with this.

so let's let's flip and you do die that around like that. And well, now we're starting to be a bit better. Now here's one thing. this ground symbol.

What do you do with this? It let's say you had to put the connector like this and your ground pin happens to be the one at the top. It's really annoying. Traditionally, ground should be at the bottom. so you know there's a lot of people who will say it.

Well, it should be like this. And then you should, you know, draw your trace going around like that and that's okay. Nothing wrong with that, that's perfectly acceptable. Or you could keep it sideways like that.

Maybe you could put it up here like this and then you could. In this case, the ground symbol is quite large, so you could have it going up like this. Either way, you know it doesn't really matter. Even some people.

And Eve even. I've done this before. I've actually put them vertically, like horizontally like that. So I actually spin it around like that to fit between pins and stuff like that.

I've had a visually small ground pin. You generally want to avoid that so you know it's up like that would be okay. all the other one down here. as I said either.

Once again, it's This is a bit messy because the ground everything's out of proportion because this is not properly designed laid out from scratches and imported project. But you kind of get the idea. I kind of would have actually preferred it down the bottom there like that. So I think that's better Now what do we do with this trace here going through our chip? Would you like? Well, let's say that you need this connector here.

Look, most of the lines for this connector are going to these up here. so would you actually run them all down here like this? and over there? you might if you're physically constrained because this chip has to be here for some reason. But generally you'd probably want that connector right up near the pins that you're actually going to be doing over here so that it'd just be a nicer way to do it. But once again, I Can understand wanting to have the connectors physically away from your schematic.

so you might have all your connectors on one side over here and just use nets for example, six of one half dozen of the other. As long as its need, you generally want to avoid all these wires running right across your schematic like that. So in this case, virtually all your signals except for this relay down here and or switch is it. And yeah, it's a physical switch and this one line going right over to the other side or all of the connectors.

So I'd be of the opinion to maybe shove that connector just in there. Either that or Nets shove the connector over to the side somewhere as long as you're consistent. So in this case, and go over here like this and we'll move it up there. We've got to change our Nets around and stuff like that.

But yeah, we could. we could tidy that up. We can. We can sneak that in there.

I Think it's probably going to be better. And these nicknames. you wouldn't have them over here like this. You'd bring them over here to match.

So this is actually gonna be much nicer if we do it like this. Here we go. You're that. How much need a does that look already compared to before? I Know these are a bit higgledy-piggledy in here, right? but that is much nicer.

So this net here okay, is buggering right off to the other side of the chip over here. You wouldn't take that line all the way around, so you kill that trace there and you would have the net and then copy that net all the way over here. Like So there you go and just get rid of all this crap running right across like this. There you go.

That's nice. Oh, and the other thing here, see how this one got this line going over here. It's like crossing here here. and here it's crossing three lines.

It doesn't need to, so of course you would up select the right wire. You drag that like that. That's much nice and generally you'd actually have it. Probably like that.

And this one here. you drag that out of the way and once again just have them crossing as fewer lines as possible. This one's a like and once again, this one is crossing here doesn't need to. so that one will come across there like that and that's just like that's just much tidier already.

So that worries. And of course, the problem we've got with this net here is that you wouldn't have that come across all those lines like that. so you'd actually just draw that in. You know you might draw something like that, for example, and that's just nicer.

And there we go that looks much neater. Once again, you could argue that that's better that you know if you wanted to put all your connectors right off to one side. but that's certainly better than the original one that we actually had here, which was going down like that, all overshot. even if this was nice and tidy down the bottom.

its I think it's just much nicer to have that connector in there like that and just a small feeling. tidiness once again, right? You would actually rotate that so it's like that and you don't want these lines coming across the pins like that. That's just silly. So you bring it out like that and that's much nicer and the same deal at the top here.

Bring that around and once again, you wouldn't have that horizontal like that. whoop. Make it vertical much nicer. And there's far too much space in here.

and the net should be over the line. so we want to go in there and move those across. much neater, much more compact. Everybody happy and again, we've got this line where the nets are over.

even if the nets were here like this. Okay, you might think okay, those nets are relatively neat, but once again, it's it's. really. you should be implying that this line is going out like this.

Okay, because this isn't like an I squared C line. so you want to put them out like that, so it just visually signifies that there's a line coming in that's much neater. And as for vertical resistors like this, do you put them off to the one side like that? Generally I would if I physically got the room I'd only put the annotations and the values vertically like that. If I didn't actually have space.

sometimes when you got all a big group a resistance bunch together, you know you might have to like put this either side like that. I've you know I've often actually done that and when I've got them all group together like that. Sometimes you know visually you don't have the space, but in this particular case, we have the space. And putting them both like that, it's just much nicer.

You don't have to told you had to read it. so put everything horizontal or designate as horizontal. If you've got the room to do it and these connectors up here, take a look at this. There's no reason to have any of that vertical.

So I'd get that and I would rotate that like that. Then you get your ground. You fix that up. You get your 5 volts here.

You maybe fix that up like this. You have it going up like that. Of course we have to rotate all our Nets here, but you know, like that's going to be much neater. No doubt we don't need the component designator so pin display like you could keep that in there like that.

and once again, you wouldn't have some reading in that direction, some reading the other. Generally, you're going to want the peasant. You're gonna want them all reading just like the spine on a book. Reading from that direction.

And this. JTA here to here. look at the white space, just wasted and resistors not lined up and stuff like that. No, no, no new, new, new, new.

Maybe you want to line them up Or like that. There we go. That's nicer. Get them physically lined up across, like that, take up much less space.

Thank you very much. I'll tidy that up. And another thing, just keep a consistency on your designators here. you see that we've got.

If you're going to have your designator on the top and your value underneath, make sure you are consistent with that across your entire schematic. Otherwise, it's just professional. Now, if you remember this connector that we tied it up over here that's called Pin Right. There's another one over here called pin left and that's going off in a couple of traces going off right? Yeah, over to this side as well.

so you would tend to group those physically together. so I'm tempted to move those like. we kind of sort of might have to shift the rest of this over. but I'd probably put this one over here next to it.

or because one's physically right, one's physically left. I Don't know. You might argue that it's better on this side. You would have to actually go in and see where all these nets.

Aha, these nets go over to here. So yeah, it's higgledy-piggledy to all the pins. Once again, if you laid out a schematic and you have a choice of the pins in this particular case. Okay, all of our pins are in physical.

Well, they're not quite in physical. They are in physical order around the chip like this, pretty close to it. And once again, for a large chip like this, you, you might. You know, a lot of people will do that and there's nothing wrong with that at all.

It can be a good thing as I said when you're troubleshooting and stuff like that. but then it makes a difference when you're trying to group your stuff together in your schematic. So if you you either decide to go for the full physical ping configuration around your chip, or you decide Nope. I'm gonna group my functions together and then you would have.

In fact, then once you've once you do that and your pins, you can swap your pins willy-nilly inside the chip. Once you decide to do that, you wouldn't have any of these crossover lines in here like this. You just have all the pins going straight in and then rearrange the pins on your chip. so it's all just neat and tidy like that.

But then you don't get the physical pin configuration. Yeah, everything's a trade-off and just a small touch here because these are like the same type of connector ones called pin Left, ones called pin right. Just make sure that if you put pin eight at the top, on one and pin one, and on the bottom, be consistent with the other one over here. Now, you've heard me mention consistency before in schematics and it's very important.

Not only like a placement of things you know, you keep all the texting in one orientation. for example, like reading like tilting your head like this and reading the same direction, keeping them above and below and and all sorts of stuff, it also extends to the the schematic symbols themselves. In this case, we have the two traditional types of schematic symbols we have, like the dual plate one like that and we also have the one with the flat top and the and the curved bottom and there's no consistency. They've mixed and matched both there for both low value items like non polarized capacitors, then if we go over here, we've got different types of resistors.

We've got the square one here. a bit of a square resistor fanboy, but I've got. You know, if it's a nostalgia for the old zig zagging resistor, one doesn't matter which one you use makes a rat's ass difference, but be consistent in the types of schematic symbols that you actually use. It's important, right? So now we really have to reformat this thing because this is like this was my first thing with this schematic that I went.

This is so bad. Not only is that BNC connector rotated like that, there's no left/right flow in it and then look having the this is the tert that we've got for 200 ohm resistors in parallel here going down ground, not only ground symbol upside down. this is actually a switch symbol here. It's not very good so it doesn't have like the circular contact so the switch symbols not drawn properly, stuff like that.

but you know that's neither here nor there. So we need to like reorient this whole thing. and oh it's not gonna be fun. So the first thing I'm going to do is just split these things up because really, we want to be able to rotate this and then put it in the right orientation.

I won't bore you with all the details of tidying this up. That's not the point. Okay so what we've got here is this abomination where the resistors are on this side here. didn't make sense vertically and doesn't make sense horizontally either.

The B and C is the input for this entire project. So you want it to be on the right hand, left hand side of your schematic. Remember, input signals on the left flow through your page, output signals on the right. So first of all, we want to get this poor B and C.

Well let's just look, let's just get it out of here right? So we want it to be like over here, like this. all right now. we don't need to ground symbols so we'll get rid of that and we'll just join one right? So this. is now starting to make a lot more sense.

So how do we orient the switch? I Don't know? You could like, maybe have it like that? perhaps? Yeah, that's which is better off being horizontal like that. This is going to be much neater if we just do it like that. Okay, so we've got input signal like that going through our switch and then it's obvious we don't want to remember. no diagonal lines on here and then it's obvious that bingo, that's much nicer.

And then of course the input has to bypass this like that and that will go off to the rest of our circuit. Now that's much more obvious and then we can do something nice like. Here's where we start adding some niceties to our schematic. Then we can maybe add a note there like that.

10 Meg 50 ohm termination like that. So you know it just makes it obvious that what that part of the circuit is doing. if it wasn't electrically obvious, just adding like little notes and things like that can make a huge difference. And of course you'd probably like do this at the end.

you wouldn't necessarily like. Well, because this is duplicated, you'd add it now so that when you duplicate this in your schematic and it's just copy over. But often you'll do like a a like a note annotation thing at the end where you finish your schematic electrically and it's all okay. and then you'd go through and just you know add like nice little notes and little formulas and little other little niceties around your schematic.

so this one here requires a bit of thought. Okay, we've already got our photo. Moss Real A like this. It's a MOSFET in there with a diode which then switches it off.

It's basically a an electrical a Moss relay. It's just like a regular contact relays button because the switch contacts are here and here I Guess you could argue that. Well okay you know we should probably like have that in line like that. but the problem is so that like your input signal here you go.

so your input signal goes in here and that comes out here. but then that's not a use of and that's not a good use of like compact space, especially if you look at how much vertical height is required there. It's actually more than the original schematic like this, so you know you might just bring it down like this or something. And then of course we got our ground upside down and so we have to look at rotating this one around.

It's yeah, it's not particularly great. I'm not a not a fan of this. Mmm, that's sort of. you know, Fairly descriptive.

Okay, your signal comes in here that BNC connectors I know it's back to front, it's drawn back to front I'm not going to bother. edit in the symbol, it's just it's like the signal comes out physically out of the BNC or get out of the B and C Though, it's just it's nuts. Anyway, that's a very poorly drawn symbol to begin with, but let's not go there anyway. In then, that, of course, bypasses around here and it's obvious that input termination nice And then this is obviously your photo must relay for your AC coupling.

So it selects AC coupling or DC coupling. and then we've got a 10 Meg resistor going to ground on this side here. and well, we haven't drawn our haven't finished drawing our input signal like that. There we go.

and then we've got our lead driver up here to turn the relay off and on. And the big part of schematic design is choosing good net names. Descriptive net names: I mean there's no limit to how long you can make your net name usually apart from, you know, physical limit like looks really long so you don't want to put war and peace in there, right? But in this case, II I don't know it. E stands for enable that's probably enabled like an AC SW.

It's obvious to me that that's AC switch for just AC switch. There's no need to put the E and underscore on the front of it. It's just obvious like AC switch for would have been fine, but you know. Description: Net name Choosing descriptive net names.

bit of an art in itself. Actually, I've decided what I'm gonna do is I'm actually gonna flip this up because it makes no sense having this signal come down to the bottom and the lid up there. So rather than redraw the symbol I'm just going to work with what we've got. and I'm actually going to flip it around flippity doo-dah like that.

So that's going to be much nicer so that our our signal flow is straight in like that, our AC coupling like that and once again, we'll get rid of, get get rid of this this because that's untidy and then we'll take our resistor and we'll move that around and we'll rotate that. Get Rid of that. Bingo! I Know this looks messy cuz we're not on the grid. Okay, but you know, stick with me.

Stick with me. And here's another thing. Okay, don't put 0.01 Micro Farad's I Know there's lots of decimal point fanboys out there, but decimal points can get lost when you do printouts and stuff like that. That's why you would call that one either a 10 Nano Farad.

Okay, this is actually there was a time back, probably mid 80s people start early to mid 80s. I Think it was was the great Nanofarad debate where oh like before this, they never actually used Nano Farad's and schematics. It was Micro Farad's and you put 0.001 micro Farad's Or you'd put puff pico farads. Ooh nobody was using Nano Farad's back then anyway or so.

but it's all changed these days. So you'd put that as engineering notation, right? Proper engineering notation without disappoint. A hundred Nano Farad's like that, or some people prefer to zero you one. Like that, they actually put the multiplier in the middle of where the decimal point would normally go.

for example, so you know, oh sorry, that's a Tenon, so that would be 0 in 0 1 like that, but you would like no I'd prefer a hundred Nano Ferrets thank you very much. or just a hundred in something like that. But don't try and avoid decimal points like that. So there you go already.

It's looking like a much nicer schematic. It comes in like this: We've got our switchable input termination and then it flows in. We've got our AC coupling off, or on with the control. Down the bottom of that, we've got a 10 meter resistor on the output and then we just take the rest of this and just line that up like that.

Once again, you're maybe you've got some dead space down there. So to do that, you might sort of, you know, have it down here like this and then have you why I go up there like that. Either way, you know it's okay. Now in this particular case, because they're so like they're close physically close together like this.

This is might be a somewhere where I don't actually put the the designator on one side and the value on the other side like that. I Know we're sort of mixing them up here. Here's top and bottom like that: this is top and bottom. You know we could put it like that, but then it might be too close to the one down below.

So whether or not it's side to side like that or one above the other, it doesn't, Mara is once again, consistency is key. Okay, so we if we're going to put it like that for that one, then we'd keep it like that for that one and so forth. Now, whether or not you actually put one top bottom here we go. It's a little bit messy now, so yeah, we're gonna have to drag those out, but it's like this one, for example, could be on the bottom.

Like that this one's on the top, that one's on the bottom. There's nothing wrong with that. That's fine as long as you know it once again, like grouping. Sometimes you're just physically constrained by the components, so in there you can move them around and do that sort of stuff.

But yeah, you know, six or one half dozen the other. as long as you can. system and just a couple of our consistency tidy up issues here: I wouldn't have those lines there I'd bring them all down there like that I know they're different colors I know the Junction's some Junction like they shouldn't be there. But this is the problems with like tidy up schematics like this.

Unfortunately, it's not great. doesn't look like what I'd normally do, but hopefully you're getting the idea now. I'd actually place a port here because this is like essentially this whole like this is like the input block. Okay, so in yeah, when you're doing blocks like this, generally you wouldn't use a net.

It makes no electrical difference. It makes no schematic difference. so you could just have the net there which is just fine going off just like you. you know, just like we had the you know, the nets over here and and stuff like that, that's fine, but because they're all within the one block.

but when you've got like signals going out of blocks I Generally like prefer to use like a port, it just sort of signifies that it's sort of exiting a block. once again, electrically, there's no difference whatsoever. Schematic using it if you want I just use a port, but it doesn't matter, we'll just stick with the net once again. I've just put some more label in there this so of this different sections input termination AC coupling and this is I Think it's like some sort of input, just selectable input filter in here I'm not sure of the exact function on this input for example, like you might put in like you might have a much more detailed blocking, you might actually put in the formula to calculate or at least tell you what the different you know frequency components of the filter are.

for example, you know that's just a nice touch on a schematic. So that, okay, it's an input filter, right? So you go so you go from. Actually, you know you go from not having that at all and people have to, you know, guess. Oh yeah, that's a It looks like oh yeah, there's a resistor and the capacitor there, another resistor and capacitor.

here. this one's got two. They're obviously different values that's doing. You know it's doing some filtering.

so then the label actually gives you another level of description again. and then if you go in more detailed in there, it can actually give you. yeah, this one's designed for, you know, twenty Meg bandwidth limit for example. And to tell you that, and then you could often put that right next to which side of the switch it's on as well.

So you could, physically, you know, make this note smaller and like put it okay on this side of the switch, say it might be 20 mega bandwidth limit or whatever. the other one is full bandwidth. Something like that, you know, adding nice descriptive stuff to schematics like this. it's a real big thing.

and I did I did this extensively in my Power Supply Micro Supply Power Supply project. The schematic for that I might have to link that one in, but it's got like extensive notes added to the schematic and this is where I'm going to completely cheat and just copy this from one channel to the next. so this schematic won't be electrically electrically correct. So yeah, sorry about that, but yeah anyway.

See, it's taken up more space than before, but at least it has some resemblance of signal flow going from one side to the other like that. And because not only do we have the signal flow within the block flowing from left to right, then of course we need to move that literally onto the left-hand side of the schematic so that your input signals are over there. Because as I said, right at the start, the first thing I'm looking for when I look at the schematic I know it's a digital storage scope. So I'm looking right.

Where are the B and C inputs I Want to start? You know, follow the money I want to start right at the input and I want to follow the signal through like that. So there you go. There's our input section and if you wanted to get fancy pantsy and then if we wanted to, we could add a nice little block around that and then just label that like input section something like that. or you know, input switching, input amplifiers, or whatever.

So it just signifies breaking up the block seer circuit. So there you go. That's all of our input circuit all over there with the four different channels like that. and the signal flows from left through to right into that block.

and then it flows out of that block. And as I said, like you might if you were doing moldy sheet schematics, that would be its on its own sheet for example. and then you'd have ports going out to the next page. But we're just going to keep this to a single page Schematic: Alright, so we've tidied up front-end Brilliant.

Well, this down here. this is ugly. Like as I said, like this should be a proper Op-amp to show what's going on here. I Definitely wouldn't have chosen the physical pin ship layout here and then this at the only way we know what on earth this is is by its lane name here.

Again, switch to A. So obviously we've got switchable gain. A B Here it looks like it's just an analog switch actually. Yes, the 741 G but I don't know that offhand, but looks like an analog switch.

But oh, let's just look at how they've created this schematic symbol. This pins going off like this. that's going off like this. There's no consistency.

Look at the in the in your schematic symbols. Look at the thick line around here and the thin line around this one. Keep all your schematic symbols consistent. Please.

Once again, we've got some redundant nets in this part of the section here that's supposed to highlight where else it goes in the circuit. He goes absolutely nowhere and once again, you might put in. put it's that, don't net names that don't go anywhere if they contain a a useful descriptor for example, in in this case, it does. Once again.

I've rotated all of these things. I've greatly tidied up this because it just looked like shocking. I've even tied it some of that one up right. It looked really bad.

So if you wanted to keep those net names that's you know that's that's. fine and dandy by all means. Do that. Stretch it out like that.

You have to fix this one up here and then put your net names in there. no workers, look at that, Then just once again, line them up properly. Snug grids Not working properly here. Ordinarily you have a nice snap grid There you go, and that looks actually quite reasonable.

And I've taken out the line that actually goes through the chip here, so you can tell. Okay, this is the output of the Op Amp, so it doesn't flow when this is where the Op Amp schematic symbol would have actually been. nicer than just the physical layout of the chippy. Okay, but you can see that the output of so it's actually the signals flowing back this way.

which is not really. You know, it's not terrific. So it's flowing through this analog switch. Here, it's showing it's flowing through either of these gain resistors here, with just some compensation capacitance either side.

and then it's coming back to the negative pin. So that's like the feedback on your traditional Op-amp circuit. So yeah, that's not the best stake. and then like, where's our input signal here? it is in IE -1 Which well, it should be coming from somewhere.

I Think it came. It should be coming from our yeah in B - Ok, so it comes from. it should be coming from our thing up here. I Just haven't got my nickname so properly.

So it comes from here over to here. That's no good. We need to physically move it. Ok, so we want our gain stage to be right next to all right.

So I got our input circuit. Then the signal flows remember, from left to right into our gain stage. So now I've got to move our gain stage up here. I'm gonna keep this max chip.

but hang on. We need to bugger this off up. so let's drag this one. It's hard.

It's hard. all the humanity, the humanity. But anyway, let's keep it consistent because we want to follow for gain stages like this. so we want them to be nicely in line and flow from once again, left to right.

So we pretty much have to redraw this abomination. But we're going to stick with the one chip between the two channels because even though that's the worst schematic symbol ever for an Op-amp it's like, why is it elongated like that and it says let's just not go there and I Just noticed this capacitor is actually upside down. By convention, the flat plate of this capacitor is the positive one. Even though this symbol doesn't have that and it might not be a polarized capacitor, it's just it's just wrong.

At dance, it's just wrong. Okay, so this is an ideal and I don't like it at all. but for the expediency of doing this, I'm just going to leave that chip there. but as you can see, it would have been much nicer to have like an actual Op-amp symbol there.

But anyway, once again, I don't like that at all. But as you can hopefully see, this will at least be consistent when we duplicate this once again. I'm for the expediency of this I think I'll just delete all that so this won't be electrically good I've given up trying to make this an electrically good schematic. It's too much work doing this in out.

It's probably more than enough work doing it in Eagle But anyway. so, but at least it'll visually look good at the end. As you can hopefully see, this is now starting to make some flow sense. Like this input block over here goes into input gain stage and then that will flow out into our ADC over here beauty.

and once again, I've might add some notes in there. It's not the tie deist you know thing. I can space it a bit better. but once again, this is the gain stage.

I'm not sure the exact gain here. whatever it looks like, you know, times 1 times 10 or whatever. I'm not sure you know. semantics doesn't matter.

So there we go. we could just add some text input stage like that. gain stage like that. no workers and now we have our ADC So we need to now tidy that up and so hopefully you can already see the improvement with our signal flow like this.

we're going to flow into our ABCs if you, if you remember our original schematic like this. Ok, here was our input. It flowed down like this and somehow went around our Op amp like this and then went back up past the input stage up to the ADC up here and then somehow into these analog switches over here and like and then it goes from the output of this over back right. So it's the flowing back left into the FPGA and like I said like it's just nuts.

So already you can see that we've got a signal flow through the different stages. That's why an oscilloscope like this is a classic example of multiple signal stage flow like this and it lends itself very well to a our schematic. Like a nice visual schematic. Actually, what we have to do is actually sneak another stage in here because this is actually the over sampling stage.

here. It is here. So it's actually got to go in here because this is where it routes the signals either all four channels into the ADC or into the biggest. We've got two ADCs dual channels each so that IVA routes all four inputs through to all four ABCs or it actually duplicates or at two of the channels down into the other ADC so they can get twice the sample rate.

So really, that block physically in terms of signal flow should go in here. even though it's just these two little dinky analog switches here. needs to go here. It's part of the signal flow.

Keep getting left and right on the camera. It's really weird. Think backwards. Now it's this staging your schematic that you start deciding well.

I Just don't have an infinite amount of room going across the page like this. so we're going to have to wrap it. But there's our four stages: input stage, gain stage, over sample selection, and ADC. Then the ADC flows into the FPGA down here and it looks like most of those pins d4, C and all that.

There looks like they're all down the bottom here. so if you late, if you still had room to flow it out like this, then you would arrange the pins on your ADC so that the outputs and you'd range the pin out on your ADC here because you'll notice that the pin out of the ADC is not in physical pin of format. so you have the freedom to move those pins anywhere you want. You would group the digital outputs here on the other side of the chip.

So when you create in the schematic component for this Max 19, 506 ADC you'd have the analog inputs on one side and all your other miscellaneous clock and stuff like that you'd have. This is like us about like I'm not going to go in there and start modifying components to make this schematic absolutely perfect. Sorry about that but you would have you've got analog on one side. analog input clock inputs you can.

You don't have to separate your analog from your digital side like that. You do it signal flow. So it doesn't matter whether as analog signals coming in or digital signals coming in, they should be on the left-hand side of your chip and then your outputs. ie.

your digital outputs like this should orbit and maybe power. Well you can say Powers is an input as well. You might put that it doesn't matter which side you put the power on really, but it might put them on the top and bottom of the chip for example. That's very common, but once again and don't want to start a flame law.

but there are those who never put pins top and bottom over your chips because that just doesn't look right. They like having all pins on one side including power and ground or like inputs and all the outputs on the other side. Whichever way you want to do, it doesn't matter, but this one side of they didn't put any thought into this schematic component and you should 14. which is another reason why you shouldn't just use the library component supplied with your schematic package because I know it's easy, but then it doesn't make for a good look in schematic.

it's just hard. Often you know it could be just being like pin physical pin configuration. and for an ADC no redraw the schematic symbol so that the signals flow in two out. but I'm not going to bother doing that.

but if you could then you could have all the input signals then just going out the side of this thing and straight into your and then you'd put your FPGA over here. But we don't have the luxury to do that. We're kind of I know we could. We could put the FPGA over here, but I'm already using an A1 schematic sheet.

So yeah, it's all the trade-off you might put on it. You know, as I said, you might have all this on one schematic sheet. This could all be like your input stage and you conversion. We might have that on one sheet and then you might have your digital processing and power supplies on the other sheet to sheet schematic.

That would be quite reasonable. in this particular case. I Think All right. So now I'm going to create a power supply block over here like this.

You can put it, you know. Anyway, like it doesn't matter. I have power supply block. then I have CPU block.

Then I'll have an output block like this. so we're getting tidier into. Oh, we've got an indicator block as well. so we're getting tighter and tidier.

Where else have we got some? Is that it for our power supply? I Think that might be in need. Where's the input? Where's the power supply connected? Because you want to include the power supply connector that's on the USB Where's our USB connector? No. Here it is. We want that to be over on the other side too.

Because well, so we're going to have to include the power supply and our it looks like we've got a serial is that an FTDI thing or something? So we'll yeah, we'll work that over there too. So in our old schematic look, this was a real mess. Like right in the middle of the schematic is where you don't want to have your five volt, your USB and five volt power input. So look at like it's just so.

I've put it over here. Here it is. So your five old input from here goes into your switch. No worries, you switches on or off.

It's not the best switch chromatic as I said. but then it comes in five volts. Bob's your uncle, No worries. So and then we put our ground like that.

That's never have anything at forty five or odd degrees like that. Bingo. Okay, we've got our input and then we can put our data lines going into our chip because we're gonna cross them over like that. It's It's not the best here.

Here we go the the alignments. not the best team. Your pleases? please forgive me. Okay, there we go.

That's much better. Now we're talking. but look at this. This is a bit higgledy-piggledy indignant.

So it's me of our capacitor over there. Geez, what a shocker. Terrible. Muriel Anyway, there you go There we go.

and we've got some pin numbers. like on crystals and stuff like that. You don't need your PIN numbers on your crystal like that's. just like having pin numbers on your capacitor or your resistor.

It's just, you know, it's just pointless. And and the three volt up three volt rail like this. that? obviously that's around, so we'd actually duplicate that. You wouldn't run another one over on the other side like you wouldn't run a wire over there.

you could, but it's probably just needed to go like that. For example, for the ground and the ground. oh, it's upside down, so whether or not you'd actually have it going all the way through, Some people would prefer that, others would prefer to snake it up I am not that fast I'll just take it through, but there's a lot of argument to be made that you wouldn't take it all the way through like that. but from a clarity point