Problems with MIDI-CV converter

[Isac Georg Jensen]

Hello

I'm not sure if it's okay to discuss Midi-CV converters on the
synth-diy, but I'm in trouble, so here goes:

I have constructed a Midi-CV converter based on the Motorola 68HC705C8
microprocessor. The reason that I have chosen this is that I could have
it for free and it's got an internal UART (opposed to the 68HC705P3). 

So far I have the following up and running; 8 CV out's (0 - 5V) each
with gate (0 or 5V). LCD display and some buttons. For test purposes I
have a PC running a terminal program sending at 9600 bps. The
u-processor recognizes everything I type at the PC. Now comes the
problem. When I connect a keyboard/synth (Korg M1) to the interface and
sets the 68HC705 to receive at 31.250 kbps, I can't make anything of the
recepted signals. When I press a key on the synth the Midi-CV receives
something completely different. 

The optocoupler is a CNY-17-4 which I have seen in a lot of other midi
projects (rise and fall time 2 usecs.). I would like to check the rate
at which the M1 sends, but I can't trigger my oscilloscope if there's no
periodic signal (I'm an alright keyboard player, but I'm not THAT fast,
or steady!). 

Anyone with similar experience or any ideas ?

I'm sorry if I have bored any of you, but this really drives me nuts !

- I.G.Jensen

mail:

igjensen at vip.cybercity.dk