Clock PCB (With bodge!) - Making an 8 Bit pipelined CPU - Part 88

[@kalj7]

Watching those buttons melt was painful! Glad you were able to sort it out .

[@weirdboyjim]

That was the first time I had used hot air on anything with plastic parts, I'll hopefully not make the mistake again.

[@edabean007]

loving this series. thank you.

[@weirdboyjim]

You are very welcome thanks bean.

[@rlbjr898]

Thank you! Perfect video for a Saturday morning sipping tea!

[@weirdboyjim]

Glad to be of use Bob! Hope you enjoyed!

[@FrankGevaerts]

The entire thing is starting to look really neat. I'm looking forward to see it all finished!

[@weirdboyjim]

You and me both Frank! The display circuit is going to be significant but the core cpu is close now.

[@TroySchrapel]

Looking great, James. Can't wait to see the PCB-ised ALU.

[@weirdboyjim]

Thanks Troy! I also really want to see that! Sadly I have to a whole bunch of work first! ;-)

[@genxtech5584]

Great project mate. I've been watching this since your first video and you've really done a good job here. Love seeing this come together. If it were me I might be tempted to leave that bodge on there, like a scar from an old battle to remind you of the good times :). Keep it up can't wait for the next video to drop.

[@weirdboyjim]

Thank Louis, glad to hear you have stuck around and I haven't driven you off ;-) I will replace the board, but you'll notice I put a version number on them, so the scars will always be there in spirit.

[@DustinWatts]

Great step forward! And congratulations on your first bodge ;)

[@weirdboyjim]

Thanks Dustin! I'm sure it will be the first of many!

[@brandonmack111]

Very nice :) you had to have a major bodge eventually, it's almost amazing it took this long. You've definitely got a great track record so far off designing functional PCBs.

[@weirdboyjim]

Thanks Brandon, the good record is mostly down to my building everything on breadboard first, this one was really just a transcription error.

[@brandonmack111]

@@weirdboyjim I feel like that's the right way to do any complex circuit, so you can make sure it works before you spend a lot of money on it.

[@th3magist3r]

I really love this video series. I learn something new each time. Thank you!

[@weirdboyjim]

That's good to hear Alexandros. I'm glad you are finding the series interesting.

[@richardlighthouse5328]

Can't wait to see your plans for ALU. Interested how are going to incorporate diode rom.

[@weirdboyjim]

I'm hoping to do the diode rom a bit more spaced out so I can write the operations next to each row, that way you can see the control line pattern in the diodes.

[@wChris_]

@@weirdboyjim I thought of Doing it as a Matrix, with horizontal connections on the Top and Vertical on the Bottom and Vias connecting the Control lines at the right places

[@RoamingAdhocrat]

That's me caught up! Binged the entire series since the Makerscast panel from I think last weekend! Very, very satisfying to see it come together :D The series inspires a drinking game. Take a shot every time: - miswired VCC or ground to a chip - double if the chip's the wrong way round - "Be bold!" followed by something working flawlessly first time - Selection of a 74x193 - real-time audio but fast-forward video - Auto-Route, Fill, Buy It Now That last one in particular - I ordered a PCB a year ago but the design was wrong and it was rejected. I need to go ahead and simply order PCBs.

[@weirdboyjim]

Very glad you have enjoyed it, very sorry to say the build will feel very slow from here on out. Your drinking game could be very counterproductive, that looks like a lot of drinking. Hopefully I've been making less mistakes as time goes on, I do try and show everything including the mistakes. My intention was always to create a build log rather than some kind of how-to tutorial.

[@RoamingAdhocrat]

@@weirdboyjim What I really appreciate is while your skills have developed in electronics, PCB design, soldering etc - you started this as an accomplished assembly programmer who knows intimately what a computer should do on this level, and I appreciate seeing your expertise there shine through the whole project.

[@AndyGoth111]

My favorite way to cut traces (tracks) is an electric engraving tool. This is a big part of my stripboard technique. I use a marker to draw where I'm going to cut, double-check my marks, then go over my marks with the engraver. A pencil-sized AAA battery-powered tool does the job just fine.

[@weirdboyjim]

Interesting, probably easier to be sure you have separated the conductors if you create a visible gap.

[@jimmy21584]

Looking great regardless! The old trick I use for breaking traces when all else fails, is to spin a small drill bit over it.

[@weirdboyjim]

I've used a drill bit on strip board, but for pcb's like these I find it inaccurate. With the knife though I'm always worried I might leave a join (Or something that could join when the board flexes)

[@milesrout]

Great job! I've spent the last week or so designing my pipeline. I've managed to get it from 8 to 4 stages with some careful thought and an extra bus, which is nice.

[@weirdboyjim]

That's sounding good. Be interesting to hear about your design. when I'm done with this cpu I may do a video talking about the design things I'd do differently if I were to do it again.

[@lawrencemanning]

@@weirdboyjim sounds fantastic. I'd love to see those ideas elaborated into paper designs, even if you have no intention of building them. :)

[@jerril42]

Thanks James. That made my morning. Take Care.

[@weirdboyjim]

Thanks Jerril! Glad it's still of interest.

[@MrRlnansel]

Excellent work. I find that a good sharp #11 X-Acto blade works well for cutting traces. A little bit of heat from the soldering iron will lift the middle bit of the trace between two cuts, though you want to make very sure the lifted bit doesn't make it's way back to the board.

[@weirdboyjim]

That sounds about right, I'll go blade shopping when I get a chance. It's only temporary though as I plan to replace the pcb next time I order some boards.

[@UnexpectedMaker]

Overdue for a bodge? It's like opening the valve at the pub... once open, it never closes properly ;) Glad to see it's all coming together so nicely! I think you should change the bottom connecting PCB from green to black to make it stand out less. Cosmetics is super important to a home-brew CPU ;)

[@weirdboyjim]

Don't say that Seon! The colour scheme is currently "Classic programmer", will be nice to have the big unifying backplane at the end but right now I'm thinking more about what i'll call it rather than what colour the backplane will be.

[@benjaminargenziano5851]

Good stuff! Can you also add a watchdog timer to this module?

[@weirdboyjim]

That wouldn't be too difficult, but you would need another input from the main cpu to reset the timer.

[@edgeeffect]

I'm always on the lookout for new stuff to watch.... do you have a link to this "Brian Locke" of which you speak? I love the delivery times in these videos.... they always arrive faster than if you were etching them yourself. ;) We are indeed a strange breed... "oh great I've made a mistake, I'll have to budge that" :D :D

[@weirdboyjim]

His channel is a secret, Lough'ed away for only those in the know to find.

[@TheEmbeddedHobbyist]

For times when you just have two pins swapped over just lift the pins up and run a fine wire between the pin and the pad it should go to. Enamel copper wire does this great, and you can get it by taking any old radio apart for the IF transformer windings.

[@weirdboyjim]

I have various gauges of ecw around anyway. I couldn't to that on this one since the resistors connections were swapped, but there were other connections that needed to remain unswapped.

[@AmauryJacquot]

you may want to use a piece of kapton on the button next time, it seems they didn't like to be too crispy

[@weirdboyjim]

Yes, I used a bit of Kapton when I replaced the break button. On the fixed board I may do that, or just hand solder them.

[@ncot_tech]

Is it normal for the plastic on those tact switches to melt a bit? Or is that just a side effect of using hot air for soldering them?

[@weirdboyjim]

Definitely not normal. These devices are designed to be soldered in a reflow oven with a very precise temperature curve. With the handheld hot air it's far too easy to overheat them, most components are a bit more robust but these are obviously not. The one I replaced was ok because I used a bit of Kapton tape to project it, when I do the updated board i'll either do that or hand solder all the switches.

[@JohnDlugosz]

I remember there were chips that contained two or four 555 timers. I see you used two separate 555's rather than one of those.

[@weirdboyjim]

My decisions won't necessarily align with other people but I have my reasons. I wanted to keep the 3 clock sources as separate as possible on the diagrams, using a 556 would have blurred the schematic more but also added another chip to track to my storage that would only be used in one place in the build.

[@matthewpeterson5159]

Not that it matters but, interesting tidbit: they actually make sockets specifically for oscillators in that package (DigiKey part # A463-ND) :)

[@weirdboyjim]

I've seen those, I couldn't find them from the supplier I was actually ordering from though. Mouser has the longer ones but I couldn't find the shorter ones from them.

[@TomStorey96]

@@weirdboyjim I tend to use a 14 pin socket, because you can then cater for both the 8 and 14 pin footprint oscillator packages.

[@brooksbryant2478]

I was thinking about using your clock design for my build but I didn’t see the schematic on your easyeda profile, is there anywhere I can get it?

[@weirdboyjim]

The clock needed a couple of bodges, I usually only like to release the schematics once I've shown the resulting on board on video and I haven't gotten around to testing the revised board. I've had a few people ask about that so I'll see if I can get to it in the sooner rather than later.

[@TroySchrapel]

Hey James. I'm thinking of starting a new project and moving to PCBs and was going to start with your clock module as a trial. I checked your EasyEDA profile and can't see it there. Is the schematic it available?

[@weirdboyjim]

I usually share designs out when I've tested them as working. I've not tested my fixed version yet. If you really want it sooner follow me on easyeda and message me your username, I'll see if I can work out how to share it. Your own risk if i've messed it up again though.

[@TroySchrapel]

​@@weirdboyjim Thanks, James. Sent you a message in EasyEDA. Understand no guarantees since it's untested.

[@grahammitchell4811]

James, any idea when you'll be releasing the clock module? That's where I want to start as well.

[@TroySchrapel]

I ended up building a clock module heavily influenced by this one with a few minor changes. I've only built it on my custom proto card for my backplane so far. I do plan on a custom PCB for it.

[@LeoBerardino]

Are you thinking on open the project as opensource in the future?

[@weirdboyjim]

It's pretty much all out there anyway, eventually I suppose I'll have to tidy it all up and do some kind of formal release.

[@AJB2K3]

Looking good

[@weirdboyjim]

Thanks Adam!

[@PaulasTechStuff]

Nice work, but treat yourself to some Kynar wire for mod wires :)

[@weirdboyjim]

Yeah, I know. Those were the trimmed ends of resistors. Worked though!

[@greje656]

awesome

[@weirdboyjim]

Thanks!

[@twobob]

I do believe I am, yup, am looking at a computer.

[@weirdboyjim]

That was the plan!