The rise of FreHD

[stephen_usher]

Can you feed the wires out of, say, the cassette port?

[rubber_jonnie]

Can you feed the wires out of, say, the cassette port?

I need to figure out where the space is as there are some grilles in the bottom that I may be able to slide the toggle through. There are definitely options.

[rubber_jonnie]

So I managed to get the switch sorted, I kept it on the outside, secured with a dab of superglue (A compromise, not ideal but better than a hole) and manufactured a small 3 pin plug to allow for disassembly if I need to go inside again:

PXL_20231116_230109278.jpg

Feeding up inside through the lower grille:

PXL_20231116_230113365.jpg

And the mainboard end:

PXL_20231116_231230667.jpg

Sorry for the blurriness, the camera focused on the mainboard!!

And testing time, first standard Level II:

PXL_20231116_233005420.jpg

Interestingly it says 'Radio Shack' but with the original ROMs it said 'RS'

And last but by no means least, the FreHD autoboot setting:

PXL_20231116_233032191.jpg

Not much to see other than a slightly different boot message, but fingers crossed once I get the M1 interface sorted, I'll get some activity with FreHD connected, and I've now created a suitable SD card with the basics on it.

Can't wait to finish the M1!!!

[rubber_jonnie]

OK, so I spent some time with the M1 today and have hit a roadblock.

Pins 1 & 4 are supposed to be tied together (Or 38 & 39 if using standard numbering), but when I do either, the machine fails to boot, with just a screen full of garbage, which indicates the CPU hasn't started executing code.

That is with just those 2 pins connected.

Now either I don't need them to be shorted as I have 64KB of internal RAM, or the instructions I have are missing something, so it's left languishing on the bench whilst I go figure stuff out.


Meh!!

[stephen_usher]

I guess that you don't have a full pinout of the connector.. Of course you wouldn't. :-)

[rubber_jonnie]

I guess that you don't have a full pinout of the connector.. Of course you wouldn't. :-)

I do. Bear in mind that the TRS-80 wiring is funky, in that pin 39 on the computer end of the cable matches to pin 1 of the 40 pin connector on the other end, so since my cable comes direct from the computer to the interface board, I am following the Tandy cabling convention.

But I'm clearly missing something, but something is off since tying 1 & 4 together, even with the funky wiring, the TRS won't boot.

Need to read through again, see if I missed anything. I just don't seem to be able to get my head round it!!!

[stephen_usher]

Those notes about the shorting makes no sense. Why would you short RAS and A10 ever? It would mean that whenever a RAM row was selected then A10 would be selected, similarly the other way around.

[rubber_jonnie]

Those notes about the shorting makes no sense. Why would you short RAS and A10 ever? It would mean that whenever a RAM row was selected then A10 would be selected, similarly the other way around.

I know, I just don't get why it's there. I am looking for other schematics as that doesn't make sense now I've started to build it.

[Tomswork]

I finally restored my model 1 to use the 2 eprom sockets on the motherboard using the Motorola 8k by 8 eproms
Motorola MCM68766C

Works well and less stuffing in the case

Tom

[rubber_jonnie]

I finally restored my model 1 to use the 2 eprom sockets on the motherboard using the Motorola 8k by 8 eproms
Motorola MCM68766C

Works well and less stuffing in the case

Tom

Lol, and I'm adding more stuffing 😁