6502.org

So I randomly decided that I wanted to try my hand at SMD/SMT electronics for the first time ever. I had a design for a simple 65(c)02 SBC, nothing particularly unique there, and I knew the WDC parts came in QFP and PLCC packages, so I just went ahead and converted the design to use the SMT parts, along with a few minor changes/additions. For my first SMT board layout I think it turned out alright, although I definitely learned a lot along the way. Finally today (yesterday now) the boards arrived and I was quite thrilled with how they turned out, other than a minor silkscreen mistake.

But then it all came crashing down. I tried so hard and got so far, but in the end it didn't even matter. I made a rather awful mistake: I used a completely incorrect footprint for the 65C02 and 65C22s! Doh!

Thankfully though, I ended up with some unique looking coasters along with confirmation that some of the additions I made, to do with the USB interface, seem to work. Not worth the ninety bucks or so, but hey, what can I say, I'm a computer programmer, not an engineer

Oh no! That's a shame. It is one of the big differences between software and electronics: a revision or a mistake can be much more expensive in hardware. (One of the reasons that programmable logic is very handy, as reprogramming it is quick and not disruptive.)

Other than carefully checking before going ahead to manufacture - perhaps ideally get someone else to cast an eye over your work - just accepting that some of the time, maybe most of the time, your first design won't be your final design. And so that affects your idea of how much your project is going to cost.

(The cost of PCBs has come right down, but it's still a function of how big the board is, how many layers, and how rapid a turnaround you want.)

Was the mistake the scantly-clad lady on the front? LOL

I actually like the layout of the board. Oh, I'm also not a hardware engineer but a software engineer. So yeah...happened to me too. My first SBC is a small green coaster now. But hey...at least it has my name on it for future generations to mock...er...study. lol

I was saved from a similar fate by a comment I read somewhere about using a scale-accurate printout of the PCB to check all the footprints prior to sending the Gerbers off. It's also helpful in making sure the housings of connectors and other gadgets don't step on each other, which is unfortunately is something I learned only after being bitten by it. (In the pic below, the bottom left pin header is too close to the IC socket for a ribbon cable connector to fit comfortably. This printout came from Eagle CAD but I suspect most other tools would have a similar function).

Yep, no doubt I'll be doing this a bit more thoroughly from now on.

Interestingly, I found that the WDC datasheets, as far as I can tell, do not specify a single thing about the physical device packages, such as dimensions; they only specify 'DIP', 'QFP', and 'PLCC' -- unless I'm just missing something. I actually had to find the dimensions on a StackExchange post. Not to blame WDC in any way, but it is odd; I've never seen any other datasheets like that that I can think of.
The labeling on the left side GPIO connector is missing power and ground as it is on the right side.
This is something I've been wondering about but haven't done enough research on. I was under the impression that it wouldn't be any different, essentially, than the actual ground plane...
I have signals on top and bottom and just below top I have power and ground below that.
In all honesty the aesthetic is not an insignificant part of why I did add those ground fills on top and bottom, which seemed reasonable given my assumption that it would have little effect on the function of the board. Definitely an area I'd like more solid info about, just haven't dug into that yet.
I briefly considered trying to find some hacky way to get the chips connected but really, I figure I'd be less frustrated by just re-spinning the board
Will definitely keep this one in my back pocket! I even have a printer, never used the thing though lol.

As painful as a mistake this egregious is to make, at least it wasn't entirely a waste. I did confirm that the FTDI chip and USB/external power setup works, so I guess that counts for something. That and experience.
Rev. 2 will be the one

I started doing PCB 1:1 scale prints years ago... but carry it one step further. I mount the printed PCB paper on a piece of styrofoam and then poke holes for all of the components and place them to ensure everything fits... albeit SMT bits of course.

However, I once made a PCB and used the wrong gender for a DB-9 connector! Paper sizing fits fine, but it took some head-scratching to figure our why the serial port didn't work at work at first!

Doing hardware for 35 years so I have made plenty of layout mistakes. In fact, even after retirement I still made some spectacular mistakes. Here are a couple in the last 3 years to entertain you:

pic 1: 68000 DIP is 900 mil wide, NOT 600mil

pic 2: shrink DIP64 pitch is 70 mil, not 75mil

Unless you can do some serious dead-bugging!

That seems to me very likely BDD. I recall studying your POC units carefully, and more than once applying your recommendations. All very much appreciated!

These are great Plasmo. Thanks for sharing!