MCU-less teletype terminal

his is a project I've had in mind for a while as a possible Retro Challenge 2026 (a bit later in the year).

It has come together sooner than that thanks to Hackaday introducing a Retro Computing Contest and the imminent RC2014 Assembly. Since I've been keeping logs over there, I haven't blogged about it here before now and won't repeat too much.

The idea was to make a printing teletype terminal that I could use with any RC2014. I wanted to do this without using a modern microcontroller. I've had an Alphacom printer sitting around for a long time that I've been wanting to interface with an RC2014. Appropriate technology for the controller would be a microprocessor such as a Z80 with RAM, clock, serial I/O and a baremetal terminal application on ROM. Yes, I'm describing an RC2014, dedicated to the task of being a teletype terminal. I'm thinking about shrinking this down by using an RC2014 micro, but for now my Classic is doing the job nicely.

Development of that hasn't been quick. (I've been constraining it to hobby-time.) It went even more slowly after I had to start burning each iteration of the program onto ROM. I'm doing all of the code myself. I haven't started using AI to help with that, in my day job or my hobby, and have no desire to do so.

I've logged progress over 8 project logs so far. That includes building a new keyboard (I started with an Omega MSX one I had already but I've built a better one).

Last night I successfully played one of my favourite retro games, Sargon 2 Chess. By successfully I mean that it reached some kind of conclusion. I resigned at this losing position but I'm pleased that I can not suck against this game and even beat it on level 1 sometimes.

(Sargon 2 for CP/M can print the board at each turn, but that uses a lot of paper and isn't necessary if you're very careful when making the moves on a real board.)

Comments

RC2024/10 - my entry

A while ago I made this MIDI module for RC2014: It works but a better design would have its own serial chip and port decoding. As it is, it provides the MIDI interface and a clock signal for the second SIO2 serial port. This means that it requires a little setting up and will only work for RC2014s with an SIO2 (and port B not already used). I think people might reasonably expect it to be plug-and-play and self-contained, ie do all the serial itself. My challenge to myself is to: learn how to connect a serial chip (probably 68B50 ACIA) to receive the incoming MIDI and to serialise outgoing MIDI design the module, including the port decoding write a library so that it can easily be used on any RC2014. Potential applications include a MIDI sequencer and using incoming MIDI to trigger notes on the AY or SID sound chips. Entering the Retro Challenge 2024 (aka RC2024/10) has given me an incentive to get on with this! I'm happy to see several more entries in the RC2014 catego...

IM53 8080 birthday cake

Each year I've been trying to get more creative with ideas for Spencer's birthday cake. The plan this year was to incorporate LEDs in place of candles. I eventually settled on an Altair / IMSAI / PDP -style computer since those are the type of computers that inspired his RC2014. The IMSAI 8080 has the most colourful switches as well as a name that I could twist. The thought that it could show randomly flashing lights (as if the computer were running) and that it could also play a game of 'kill the bit' was very appealing. A plan formed to use a capacitive touch pad on the cake itself. The first job is to bake the fruitcake. I often use a 7" square tin and one of those cut in half and rearranged makes a cake of suitable proportions. Even after taking a slice off the faces to make them nice and square, there are still some rounded corners, so after putting on the marzipan, I used more marzipan as a filler to flatten the whole thing. Even though I wanted to end up w...

New MSX graphics / sound / joystick module for RC2014 / RCBus

I'm impressed at what Les has packed onto this standard-sized module. It contains an FPGA replacement for the TMS9918A, a YM/AY sound module and joystick interface. The project is open-source and is here . In MSX terms this is the VDP (vidio display processor) and PSG (programmable sound generator), thus being an alternative for both the J B Langston TMS9918A video module and Ed Brindley's YM/AY sound module and adds two joystick ports to boot. All on a single module for RC2014 or compatible computers. There's no room for the d-sub joystick ports, so headers are provided so that these ribbon cables can be used. This is a neat solution for those wishing to take advantage of Les' MSX8 system , which loads most MSX rom files along with a modified MSX BIOS from CP/M on a ROMWBW RC2014. It is hard-wired to the MSX ports for the sound and video, so it won't be suitable for those wanting to run Colecovision ROMs, for example. I'm torn myself between the real TMS ...

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