exxos's Atari, Amiga & retro forum

Well, the PCBs have been delivered today:


An initial check shows the GND, VCC and 3V3 all go to the correct places. I'll make up one board tonight and then I can hopefully move forward, re-writing the code in C.

I've put the board together and all the connections seem to go the correct places. I decided to add the DIN socket so that I can later test the board in stand-alone mode without the memory expansion board.


It fits nicely on the RAM board as a daughter board.


Oh darn! One slight problem. I forgot that the tolerance at the bottom was quite tight, so if I have the DIN socket in place it won't fit into the machine as a daughter board!


Thankfully I have one spare GAL, so after programming it with the RAM board GAL logic I can fit it to the board and use it in stand-alone mode, which is what it's going to have to be for the F2 and FP anyway.

And the system sees a hard drive! It works...


Well, it works as well as the breadboard version anyway.... hang.

Managed to get a bit further by tweaking the Python, which shouldn't have made any difference but suddenly the command processing started working.

Managed to almost format a disk...


Slow as treacle though. Takes about 10 seconds to write a sector.

I've found one minor issue with my circuit design for the board, which won't affect anything in a "production" environment but does cause problems when doing development.

The SD card interface is powered directly from the host power rail, which is separated from the Pico via a diode. This means that when the Pico is powered by the USB, for development, the SD card interface isn't getting power. The fix will be cutting a trace and running a bodge wire from the SD card's 5V to the VSYS pin on the Pico socket.

What fun. Installing the Pico SDK on a Raspberry Pi 3.

I don't think that it helps that I've put the root filesystem on an external drive as the machine keeps locking up as it's trying to swap. I may have to start again from scratch.

I'm sure you'll figure it out, but it looks fantastic, nice job.

rubber_jonnie wrote: 06 Jan 2023 09:10 I'm sure you'll figure it out, but it looks fantastic, nice job.

Yeah, it's just such a pain building the tools to get the job done.

I've ordered a Raspberry Pi400 unit via Amazon as the Pi3 isn't really up to running vs-code. The Pi4 series can boot directly off a USB drive, unlike earlier Pis. The SD card is the main performance bottleneck.

stephen_usher wrote: 06 Jan 2023 09:26

rubber_jonnie wrote: 06 Jan 2023 09:10 I'm sure you'll figure it out, but it looks fantastic, nice job.

Yeah, it's just such a pain building the tools to get the job done.

I've ordered a Raspberry Pi400 unit via Amazon as the Pi3 isn't really up to running vs-code. The Pi4 series can boot directly off a USB drive, unlike earlier Pis. The SD card is the main performance bottleneck.

I'd read that about the Pi4s, it's a useful feature to be able to boot from USB.

I've just realised that the Pi400 uses a USB-C connector for power and I don't have one. Darn!

stephen_usher wrote: 06 Jan 2023 09:33 I've just realised that the Pi400 uses a USB-C connector for power and I don't have one. Darn!

Even if you had one it probably wouldn't work, the official Pi4 PSU is 5V 3A!