The rise of FreHD

[stephen_usher]

I've found the best way to do the schematic is with labels connected to the components. Not need to do the wires manually on the PCB then as the wire map is done for me. I then use Freerouting to autoroute and Kate's your aunty.

e.g.

pcb-schematic.jpg (125.18 KiB) Viewed 183 times

[rubber_jonnie]

I've found the best way to do the schematic is with labels connected to the components. Not need to do the wires manually on the PCB then as the wire map is done for me. I then use Freerouting to autoroute and Kate's your aunty.

e.g.

pcb-schematic.jpg

Thanks for that, it may get me going.

[rubber_jonnie]

Somewhat annoyingly, the pages relating to FreHD set up by Ian Mavric seemed to disappear from where they were hosted, but I managed to find them again here: FreHD pages

This page is particularly crucial as it contains the ROM images and instructions to add autoboot to the TRS-80 Model 1 amongst other things.

Thought best to post it here, and I've added the files I downloaded so they have an alternative home.

[stephen_usher]

Maybe put them on archive.org?

[rubber_jonnie]

Maybe put them on archive.org?

They may already be there, but not looked as yet. I'll take a look.

[rubber_jonnie]

Maybe put them on archive.org?

Just checked, they are already there in the wayback machine

[rubber_jonnie]

As Dick Dastardly would say 'Drat and Double Drat'.

I've figured out a cable swap to that the edge connector pins now correctly match the pins on the 'bodge wire' M1 adaptor and it buzzes out as expected, but I'm still getting a no boot state when the M1 is connected.

Basically the machine is coming up with garbage on screen, which says to me that the Z80 isn't initialising and that the screen ram isn't being cleared.

So I need to double check the wiring is all as it should be, with no shorts and wired as expected by the TRS-80.

[rubber_jonnie]

So, whilst I think on about the M1 interface wiring, I think I'm going to get the ROM mods done.

This involves making a new double rom in a 27C256, containing the FreHD boot ROM and standard L2 basic which are switchable, removal of the original ROMs and installation, and installation of the new ROM with a few wires and a switch.

Once that's done I'll at least have had a chance to think over the M1 interface wiring.

I might do the audio mod whilst I have it open as well.

[rubber_jonnie]

Ok, so new ROM is burned and I have started the open ROM surgery prep work:

PXL_20231116_132038202.jpg (350.9 KiB) Viewed 107 times

Next step will be to make the necessary mods to the ROM chip and install in the board, then wire up everything necessary to make the single 27c256 ROM (It's replacing two) work, plus a switch to flip between standard L2 basic and the version that will allow booting from FreHD. That includes A11, A12 & A13 off the back of the board and fixing the Z3 jumper block so that none of the jumpers are open.

The FreHD SD card is now prepared using the archive from Ian Mavric which I uploaded earlier. Once the machine is done I can get back to figuring out the wiring for the M1 interface and see if I can get it all to work in harmony.

[rubber_jonnie]

And the ROM upgrade is mostly done:

PXL_20231116_164323891.jpg (412.67 KiB) Viewed 95 times

All plumbed in bar a switch to flip between Level 2 basic and the autoboot FreHD ROM.

I am in a quandary now though, do I drill the case for the switch (I really don't want to) or can I find an alternative way of mounting it?