🇫🇷 Thomson MO6: Part 2 (Adding Audio Input to Load Software)
27The Thomson MO & TO range of computers (ordinateur français) are similar to the Commodore when it comes to handling cassette-based software: the computer expects a TTL-level data stream to come from the cassette player, not audio.
This presents a barrier to using the computer if you have nothing else but just the computer.
Also, the [PLAY] button on my MO6 has been glued to the cassette player chassis and so is immovable! Even if I did have an original Thomson cassette, or created one from a WAV file, I wouldn't be able to play it anyway. 🤨
My guess is that it's a really bad fix for a broken [PLAY] button. Of course, with some care & effort I should be able to repair it properly, but the issue of having to create a tape remains.
There are solutions available such as:
[1] SDLEP - a very simple solution using an Arduino & SD card interface
http://dcmoto.free.fr/bricolage/sdlep-reader/index.html
(where LEP = Lecteur Enregistreur de Programmes, i.e. cassette recorder)
[2] External audio interface - this converts an audio signal to TTL - useful for the MO5 without a Thomson cassette recorder:
http://dcmoto.free.fr/bricolage/interface_audio/index.html
But I figured, in the case of the MO6 with built-in cassette recorder, or LEP, there must be a very simple solution to inject the audio signal (i.e. WAV file being played by another computer) and get the built-in circuitry to do the TTL conversion, rather than reproducing the circuit externally.
This is my thread where this solution is discussed, along with all the great help I received:
https://forum.system-cfg.com/viewtopic.php?t=15306
After much poking & prodding (without a schematic) I settled on injecting the audio to the collector of transistor TK02, using the Amstrad CPC464 implementation as a rough guide ... but it didn't work.
It turns out I was using the wrong K7 file converter ... the TO and MO machines are incompatible and I was using a converter for the TO-series. Duh.
After more discussion, I was pointed to where the schematics & service manuals could be found which confirmed I was on the right path by choosing TK02:
http://dcmoto.free.fr/documentation/index.html
When using the correct format WAV file, and with output volume in Audacity set to 50% ... it worked!
I tried two types of WAV file - one that was created directly from the original cassette (The Way of the Tiger) and one that was converted from K7 container format (Arkanoid).
Both worked without issue.
MO-series WAV files:
http://dcmoto.free.fr/programmes/_html/support_mo_wav.html
DCMOK7 utility to convert K7-to-MO-compatible WAV file:
http://dcmoto.free.fr/emulateur/index.html
I drilled a ø6mm hole where the TV modulator would've been, installed a 3.5mm socket and then connected internally via a 3.5mm plug & socket. This is to allow me to quickly remove the top case by unplugging the cable.