Designed my own pcb, works (kinda)

[u/codeasm]

After a while i really wanted to make a pcb (or let a manufacturer produce it for me, like jlcpcb) and going from 1 idea to the next, i settled on making this somewhat universal usable pqfp-100 adapter board. The Z80 cpu was something i already had laying arround for a project, but dint want to spend too much design time if it where a dud.

Well, after designing the board, waiting a week or so. Soldering my first ever pqfp(or tqfp alike) it works ☺️ some wires to a generic z80 testboard and its walking the memory space for new instructions (all nop).

Now i need to programm a eeprom and get that pio and sio working. The pcb should also work for a RTL8019AS-LF network ic i got for a retro pc build.

[u/StackSmasher9000]

Nicely done. As long as you're not driving super high current or high-frequency things, adapter boards like that work great.

Caution: PCB design is addictive and you may find yourself making and ordering more and more as time goes on...

[u/codeasm → u/StackSmasher9000]

Thanks, yeah that was what I was wondering. couldnt immediately find minimum size trace with for this particular ic, but it does have 2 grounds and 2 power pins, i connect them both, because the DIP versions use 1 pin but its much larger. still need to add decoupling capacitors closer to this ic. My best guess is for this early testing its fine, but if I go full 4Mhz and expect proper PIO or serial port, it needs well routed wires, or at least the minimum required caps and stable clock (what im using now probbaly isnt as clean as it would like it) If I gave myself more space, slightly thicker traces might fit (and route more at the back). there was no space for trace length matching. (also, for being universal, which traces would we)

the network ic should fit, but the speed and power indeed, no idea yet, might have to mod the board. which is ok :D

Was afraid i might get addicted, what did I get myself into. thanks for the warning. i might rework a 8088 pc next, or a RP2350 board (hot air anyone? )

[u/Wait_for_BM → u/codeasm]

there was no space for trace length matching

Your break outs are may be 1/2" long at most. How close do you intended to match? There is no point of length matching unless you are talking about data windows in the hundreds of picoseconds. At which point, the connector and wire dangling off and insufficient grounds are going to be a major signal integrity issue.

FYI: Signals take 1ns to travel 6" of tracks.

[u/codeasm → u/Wait_for_BM]

I work with millimeters but I somewhat get your point. what I dint go for, was matching the wires length for my first board. someone on a discord srv asked about it before i send it to a manufacturer, and i simply wanted a board to work with, yeah, my current socket/pins setup probably not compatible with speeds that high if one where to require this. (and what PQFP chip does?) ~150 mm/ns according to chatgpt

[u/StackSmasher9000 → u/codeasm]

For low speeds like 4MHz I wouldn't worry too much. To be honest, as long as the load is close by or you transition to a shielded twisted pair after the breakout board you'll probably be completely fine.

Impedance matching is more or less a non-issue for frequencies that comparatively low and traces that short. Transmission line theory doesn't come into play either until you get data lines that are more than 1/10 of the wavelength. The wavelength of 4MHz in copper is about 70 meters, for comparison - and that trace might be 3cm long.

[u/codeasm]

if anyone would want to prevent themselves from having to recreate this or want to edit it for their own use: https://github.com/CodeAsm/PQFP-100

[u/IamTheJohn]

Nice work mate!