In Search Of Help Laying Out/Designing PCB

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Juicyblunts

Joined Nov 8, 2016
20
Hello AAC community! I am looking for someone to help me layout/design a PCB for a SAP 8-bit computer I designed. I have tried creating prototype boards of individual sections of the computer, but to be honest, I have NO IDEA what I am doing in terms of proper PCB layout and workflow, resulting in several unsuccessful prototype PCBs. I have watched hours of YouTube videos detailing the process, but I simply cannot figure out a functional layout for my board. I am wondering if there is anyone out there with the know-how and required skills to successfully layout a board design from my schematic? I will gladly pay a reasonable, agreed-upon price for the service. If you or someone you know would be interested, please let me know and I will send you my schematic files after coming to an agreement on cost of service and terms of payment. Alternatively, if anyone knows of any resources on PCB design/layout that could help me understand what I am doing wrong, I would be eternally grateful for the advice!
 

jpanhalt

Joined Jan 18, 2008
11,087
Please define your use of "SAP" ("System Applications Products?").

Are your designs original or based on the very many DIY designs on the web?
Here are just 2 examples:
https://eater.net/8bit/
https://github.com/space1649/8-bit-SAP-Breadboard-Computer-by-Space-Man

How/why is your design unable to utilize existing examples of board layouts?
Schematic and board designs:
https://easyeda.com/Deasch/Ben_Eater_SAP_8_bit_Computer-5ede60632d60463a9586ab50a022b380

You say you have made several unsuccessful prototypes. What was wrong with them? How did they fail? Can you post a picture of one of the failed versions?
 

Thread Starter

Juicyblunts

Joined Nov 8, 2016
20
Thanks for your response! SAP for my purposes stands for "Simple As Possible". Although perhaps it is not truly as "simple" as it could be.

My designs are inspired by Ben Eater's 8-bit breadboard computer. Watching his series was the inspiration behind my decision to design my own. I am using all of the same 74xx ICs so the circuitry is similar, although I have made various changes throughout. I am also implimenting ideas from the intel 8085 microprocessor (including the 16 bit program counter, 16 bit stack pointer, 8 bit high order memory address bus, and 8 bit multiplexed low order address / data bus to name a few). So my design is original in the sense that it is not a clone of anyone else's, but rather a collection of ideas from Ben Eater's design, the intel 8085, and my own tweaks, additions, and omissions.

I was unaware that there were board layouts available like that. Also, I do not have any surface mount components, nor have I ever soldered a surface mount component. My board will use all through hole components (which leads to some design challenges). Also, due to the addition of more registers, a multiplexed data bus and control hardware, a design based solely off Ben Eater's computer is unlikely to fulfill the requirements for my board layout.

Yes, I began ordering prototypes of individual sections starting with the clock. I went through 3 or 4 iterations, each time encountering a new problem. The first was due to isolated copper fill on the bottom (ground fill). The second board would not work in step mode, though I was unable to identify the problem. I do not have an oscilloscope so I probed around with my multi-meter and the problem was narrowed down, but not resolved.

Long story short: I have been planning this for a very long time and I have had to learn a great deal to come up with the design I have. I have invested a great deal of money, time and headaches into this and I would hate to see it die because I am horrible at part placement and routing traces on PCB. I am a fast learner and I love to learn new things, so if there is a tutorial, a book or other resource for PCB designing that I have missed and you think would help me understand better what I am doing wrong, then that would be just as helpful (probably more-so) than having someone design the board for me (it does feel like a failure to have someone else do it).

I think I was able to successfully upload at least one photo of a couple boards that did not work. I wasn't sure what kind of information you wanted to get from the photo so if this isn't good enough let me know and I can try again. Thanks again for your reply and taking the time to read through this.
 

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Thread Starter

Juicyblunts

Joined Nov 8, 2016
20
Update: I think I finally understand the method to this routing madness. After messing around all day with various part placement strategies, I finally have a completed board with the ALU, Accumulator, temp and flag registers. I scrutinized over every connection and every trace and have ordered a test board. If this one also ends up being a dud then I will revert back to finding someone with the skills to layout a working board, otherwise I think I have learned a few things and should be able to manage. Thanks jpanhalt for your inquiry into my problem and also for providing the links! Will update again in a few days, once the board has been soldered and powered up.
 

jpanhalt

Joined Jan 18, 2008
11,087
What program are you using for the layout?

I use a older version of EAGLE. It has "schematic capture" that ensures the schematic and board are consistent. For the schematic, it has ERC (electronic rule check) to ensure all connections are real (e.g., a wire is not just overlapping a pin, it is actually connected) and agree with assignments (e.g., VCC is not connected to VSS). That avoids missing connections on the board that look real on the schematic, but aren't.

Then for the board, there is DRC (design rule check) that looks for other errors. The section of ground plane that was not connected that you mentioned (called an "orphan" in Eagle) would have been detected. I believe most software for ECAD offers similar capabilities. They are a great help.
 
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