Thursday, April 29, 2021

Electronics Tinkerings

 I'd like to write some pithy blog articles about what I've been up to with the old electronics but I've not got the energy so I'm just going to post some pictures instead... here goes...

My first actual circuit that does something. This one drives a simple 1BPP VGA monitor signal using a few pins on a Pi Pico.

First shot of the LINK_01 BBC (BreadBoard Computer)... Here we have the Pico, which is in control of the whole thing, the VGA out, a bank of 3V3 to 5V voltage shifters and a bank of bi-directional shift registers, which I plan to use for letting the Pico read and write to RAM. There's a 65C02 up there too, buried behind my debug LED bank.

Initial work on adding the busses to the design. 16 bit address, 8 bit data and whatever else I think is worth bussing.

Now with added 8K EEPROM and RAM... I think it's the old 8K RAM I started with which has now been swapped out for a 32K one. You can see the bus sea-monstering it's way across the breadboards... I got a bit sick of the LED debug bank too and decided to use an Arduino Mega with an LCD display... this is V1. Building V2 would be a little side project on the way...

And here is V2... I bought a custom Mega shield off Amazon and soldered it all up so it's a bit neater. Added a couple of buttons so I can select stuff and a contrast knob. The display looks a bit funky here because it's changing quite fast and the light is shining right on it, which freaks it out a bit. Works though... I can snoop the data and address bus and also using the SYNC bit can show which instruction the 6502 is fetching. This data is also sent back to the Arduino serial link if you have it connected via USB. Quite pleased with that little side project.

Another side project - this time soldering. In my quest to become a competent solderer I need stuff to solder. And this calculator kit gave me a couple of hours of soldering practice and was an awful lot of fun. Recommend !

And finally a little video of it running... more stuff soon.

Backplate Musings

My original plan for the LINK_01... my first homebrew computer... was to ultimately have it built using a single PCB. But the more I think a...