Your eurika moment at 45:03 is what I do for a living! System bring up at PCB level! Debugging all kinds of IP and problems! It's super rewarding! You're stuck with what you have, trying to get the most elegant solution! Often the customer/user never knows! Those are the perfect ones! 😂

You would be surprised how many products have gone to market with errors like this that are fixed in firmware. It normally gets resolved in a subsequent updates but version one of the product will be sold with the errors fixed in code. These days it's not so common because PCBs prototypes are quick to turn around but it used to happen all the time.

Although videos about PCB-ing existing components are not as exciting (to me) as those in which you add new functionality, seeing the decrease of the breadboard-ness is very satisfying. Also, bugs make things more interesting and much more educational; specially with the two fixes. The double cable reversal one is great :D Thanks a lot for the great content!

Man, I need to re-evaluate my mental definition of a routable space! That routing was amazing! I have not yet routed anything quite so demanding, but it's good to see what's possible! Bravo!

Nice routing on that board! And an even better temporary fix for a mistake that was very easy to make on a board of that complexity. Kudos to you, James!

Schadenfreude aside, that was an epic effort. Thanks for the EasyEDA tip, loved watching all the routing.

To bad about the mistake, but cool that you found an easy temporary solution :D Can't wait to see the sprites circuit go in! This computer build is one of my favorite series on UKposts :)

I think you hit the nail on the head with your comment on ground issues. As the logic boards grow in number, the issues with signal integrity will increase. So your next step needs to be finding some Pal's, or Gals to reduce the amount of chips so you can shrink the board area. This helps with ground and signal path lengths. The fun with what to do with OTP Pal's if you made a mistake in the logic map :-)

at 7:46 I'm saying to myself "this will need 4 layers"

love it, the plug swizzle was superb! I'm curious about the sprites - the crucial question is always: how many on a line?

James, would love to hear some of your breadboard war storys. Basically the craziness of fault finding on something you just built, that use to work. I'm sure we have all been there.

I really enjoyed watching this. Your PCB layout had a zen like quality to it. Mistakes happen and I like that you share those tribulations with us.

Another great video. I am am really enjoying seeing the breadboards slowly disappearing and being replaced with actual PCBs.

This proud smile of yours, when you talk about this cable fix is soooo rewarding!

Saved by the old cable flip trick! NIIICE!

Fantastic. That board was a serious challenge for both placement and routing. I wouldn't be surprised if this one had your highest via count. I love the solution at the end. Great job! Thanks James, take care.

Love this series James! Keep it up!

Your uploads always make my day!

Excellent work. Thanks for sharing with us. Nifty fixes at the end!!

Wicked ! Take that Sod's Law, a devastating blow from the Sharminator...cheers !

Loved the temporary fixes, both software and hardware!

Excellent bodge to keep you moving, like you say there will be more mistakes for sure overall it's excellent progress! Keep it up!!

After all this, he's gonna need to build a case for this. XD Love the progress of this.

Good work James 👍

Your computer is awesome.... everything about it! Cheers, mate!

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Nice work. Thanks for sharing the mistake. We all make them. Good to see an honest presentation of design and build.

I was hoping you would not settle for a soft work around. Well done! Fantastic and fascinating build! Looking forward to the rest of this.

Brilliant fix.

Lol at first I thought by VGA you meant 'Variable Gain Amplifier.' I was so confused about why you were using a bunch of logic IC's. I couldn't imagine what black magic was going on. Now I understand you are building a Video Graphics Array input. Very cool project. I only just found your series

Haha, twist ending! Awesome 😎

So Great!!!!! Thanks James!!!

Another great vid, thanks.

It would be really cool to have a series on your programming environment and how to setup your programming environment. Also an in-depth tutorial on setting up your linker and compiler.

Yay! Happy Sunday! Tilemaps goodness! I am so stoked, now to actually watch the video. Edit: That was interesting, a few wild 90-degree track corners appeared, but very well done routing that board. I was/am a bit concerned about the mass of long straight parallel tracks on both sides of the board, won't they make for an amazing aerial? Sure, we are at most dealing with 25 MHz not even getting close to the GHz range where these things really start to matter, but there could be some capacitive coupling. It is probably fine, just one of these backseat routing opinions that are worth the electrons used to transmit them.

Hi James, I would have been tearing my hair out at that! I was extremely impressed by the software fix (although I’m not a coder so your solution is beyond me) I absolutely laughed out loud when you demonstrated your bodge by DuPont switch fix, great work, sadly one board I recently designed I made a stupid error and the resulting PCB required cut tracks and bodge wires…It did work in the end though.

I had to laugh. I got bitten by a bus reversal in the mid-80s - it was for a weird TI dual port memory chip that had bit 0 as the MSB and bit 7 as the LSB and the bits did matter in that case since they also accessed a bunch of control registers (TMS9650 if curious). I had eight tracks neatly routed at 0.025 inch pitch. One cut across all eight and eight very tiny wires later, problem solved. My eyesight might be a barrier to such a solution these days though. 😂

Love it. 😎

ah yes , invert it two times to make it right . makes sense :D . nice workaround

Hot Plate vs Hot Air vs Hand soldered comparison would be an interesting video.

Its a "cludge" that works! nice, that saves a few pennies and some time!

Funny how lateral thinking got you out of a fix there. Still amazing to see what you do. When will I get there? A few days ago my first microcontroller dev board arrived - ESP32. I've decided to leapfrog the Arduino slightly, though I am still using the Arduino IDE and also getting platform IO going on VSCode. Been trying to get the OLED to work, and after a day of tinkering and messing around with serial monitors, flashing blink sketches and some frustration, I'm sort of getting some kind of workflow going. My wife looks on amused as I get the thing to load a monochrome part-image of her face to display on it. Between Ben Eater and yourself, you've completely messed me up. I used to be a software purist, but I'm committed now and the psychological hurdles are disappearing. Thanks James!

Jaw dropping intelligence!

Try Toothpicks (or connectors) under your Board when reflowing with hotair .. it's incredible how much heat a layered birch plate (?) can suck away.. flatness .. My experience at least I have one too as workspace ;) I always find it fascinating what decisions people make when routing.. that board would be a good routing challenge :D Nice work ! Thanks :)

I obviously don't know what I'm talking about, but the red bundle in parallel to the big blue bundle in the top left look like "capacitance issues" to me. What is the "right" and "wrong" way for the resistor arrays? Or is it just "my team" saying to have to have all the markings the same way up? ;) Loved the wire-flip temporary fix... Nice!

I laughted hard at 45:58 when you revealed that fix! EDIT: I realize bus data also feeds the RAM, in the right order, so everything I wrote below is completely inaccurate. Oops! Original: Wouldn't it be possible to desolder the female bus header on the backplane, and instead solder some wires between the backplane and the board to reverse the bits? I know you're trying to avoid soldering wires, but since both the backplane and the board are temporary this would be a simple hardware fix that ensures you're not introducing other bugs with workarounds.

There are tons of bugs like yours, with similar fixes, but instead of being temporary, they went to production. Even some of the big brand PCs had bodge wires on their motherboards (can't remember the brand or the model and couldn't find it).

How do you get your Stencil sent to you in a bag, mine always comes between a pair of massive spoil boards 😢

Is there going to be a Microcontroller that will run the whole show ie taking a mode_code plus coords plus the colour and attribute and then does what is necessary to be classed a GPU.

At 11:40 I thought - that's going to cause some issues later... I think this is where the error got introduced.

What about disabling Line_Flyback pulse till the pixel is read or written.

I realise that I don't know yet how you intend to handle tile data. I have read how the NES (I think) handled the fine X scrolling, with shift registers & a multiplexer to select the correct pixel/bit. But it doesnt seem you are passing the initial scroll offset to the tile data board. I wondered therefore if you are going to pass the VgaTile0-7 plus the DisplayX0-2 "fine scroll" to tile data and get all of the pixel bits in one go (maybe 2 sets of 4 bits in one byte - rather than 4 planes). But - because you are latching the data from the RAM in a 574, wont the tiledata be one step behind DisplayX0-2 - which is not latched ? I guess latch the DisplayX0-2 value one the tile data board to bring it back into sync ? Blimmey this is complicated stuff....

what microscope do you use?

So two wrongs do make a right?

How long till we running Doom? :) Cool deal man.

I feel bad about only one thing when I watch your channel: that I was not following you from the very beginning. It takes a very long time to catch up and some of your videos require a few reviews to fully understand your explanations. It would help a little bit if you would use the standardized symbols for latches, flipflops and multiplexers, as they are easier to recognize on smaller or low resolution displays.

Arh .. you missed the "tripple check" step :)

by the way, since you keep hitting the "connector wrong way around" issue, it _looked_ like you didn't actually put any gender/pcb-sidedness on those, maybe that's the problem (as in, they seem to be the same part, on the same side, which _technically_ should make them fit, but maybe easyeda is trying to be "smart")? like i'd expect e.g. the connector to be on the front of the backplane and female while the module ones on the back of the pcb and male should orient correctly automatically... that said, better double check everything anyway, it's annoying to have your boards made and then find out one of them is the wrong way :P

James, if you'd like to borrow a reflow oven or hot plate, drop me an email. Happy to loan either/both to you for a few months.

I don't call that a bug... I call that an undocumented feature.

I suggest you walk away from a layout after you finish it. Leave it for a few days. Do anything else. Then comeback with the verification hat on and VERIFY IT! Your rushing things and making mistakes that you can avoid with much less effort than fixing them later.