Reply 20 of 32, by radiance32
Hamby wrote on 2021-12-24, 12:36:
I got to thinking about this. My thinking was, if you could connect the serial port of the 200lx to a midi adapter, you could co […]
I got to thinking about this.
My thinking was, if you could connect the serial port of the 200lx to a midi adapter, you could connect it to a midi device; an MT32 or PMA-5 or some other synth, and have audio for it.
The PMA-5 is about twice the size of the 200lx, but will run on batteries...
So I started looking up RS232 to MIDI... I guess it's not all that easy because MIDI uses an unusual baud rate and some electrical difference.
But I did discover that the gameport MIDI adapter on most sound cards puts out TTL on pins 12 and 15 (iirc) and then the MIDI cable adapter translates it into the type of signal needed by MIDI devices.
But, further, I stopped by Adafruit, and came across this featherwing MIDI adapter...
Adafruit MIDI Featherwing Kit
Theoretically, you could connect the RS232 to this device, and this device to a midi synth, and have audio (for whatever games/programs support MIDI), but you still have the baud rate issue.
So... you could connect the Featherwing to this Teensy 3.2 + Header, which has 3 UARTS, one of which could talk to the 200lx (or other device with an RS232 port) and another to the MIDI device. It would take some programming, but I think is theoretically doable.They have other, similar boards which may work better; I dunno cause I'm not very knowledgeable (yet) about electronic circuity like this.
I've also seen posts on making a midi controller from an arduino, but I'm not sure that's what's needed here. I like the Teensy because even with the featherwing adapter, it's... tiny.
Almost as small is making a midi synth from a Raspberry PI Zero 2 W. The setup here communicates via USB, but the Zero W does have UART pins and should be able to talk to the 200lx at whatever speed the 200lx wants.
The nice thing about this solution is that it will work with pretty much any vintage hardware with an RS232 port and software/games that support MIDI. Theoretically, you could even add a character lcd to the device so it would say "Insert Buckazoid" while playing Space Quest (will Space Quest play on the 200lx? I hope so...)
I already have a serdaco RS232 to MIDI converter board, which does this (and a few patched games too),
but, the problem is you lose your RS-232 port that you need for the mouse. (And, many games like Eye of the Beholder require a mouse to play)
(If you look up "cloudschatze" channel on youtube, he has several videos of an HP 200LX Palmtop with a seradco rs232 to midi converter playing
a few DOS games on a real Roland MT-32 sound module.)
But, I need the serial port for the mouse..., having the sound device on your LPT1 parallel port makes much more sense.
Also, Eye of the Beholder does'nt support MIDI / MT-32 etc, only adlib, that's why it's required to change the Adlib code (The only supported sound card) modified to with with an OPL2LPT on LPT1...
Anyways, patching a game's adlib code to go through your COM1 port should be just as easy as patching it for the LPT1 port...
PS: Serdaco has an MT-32 PI hat that you install on a RaspBerry PI 3+ and it makes it into an MT-32 compatibe softsynth with MIDI ports on the hat...
Check out my new HP 100/200LX Palmtop YouTube Channel! https://www.youtube.com/channel/UCCVChzZ62a-c4MdJWyRwdCQ