OK, I've done my homework (reading through the whole thread) and I believe I have the answer to my questions above (MCU done via direct serial, not Etherned or d8b MIDI). However, I'm surprised that the original CPU was too unreliable for the RS232 to Ethernet conversion. Maybe an embedded OS and dual boot (embedded vs. Mackie OS) on the d8b CPU would remedy this?
Concerning Marc's financing question, I'd throw in 200 bucks for such a tested and working solution without thinking twice.
I'm using XP (or Win98/ME on a 366MHz PII MMX, whenever I can...
).
As to getting completely rid of the d8b CPU/PSU:
anyhorizon wrote:The +/- 16 volt rails do a lot more than run the faders. In fact they're the main power for the board. I thought the 5 and 12 volt supplies were mainly for the board logic and CPU functions.
Peter
Off the top of my head, so don't shoot me if I'm missing something. There are three power supplies in the box.
1) The PC style PSU goes to the CPU motherboard (+/-5V and +/-12V), supplying at the same time +12 volts for the fader actuator motors, V-pot and fader position A/D converters and (regulated down from the +12 going to the motors) +5V for V-pot and fader position readout.
2) The single +5V switching PSU (Aztec) supplies the main voltage for all logic and the A/D-D/A converters, VFD, LEDs, DSPs, etc.
3) The third (linear) supply gives +/-16 volts for the analogue circuits (op-amps on inputs and outputs) as well as +48V for the phantom.
If one is ready to give up all analogue funcions (I/O, talkback, etc.) of the desk, the linear PSU can be discarded right away. If the d8b CPU motherboard is unused, you can leave out the PC style PSU as well, keeping in mind that +12V has to be supplied for the motors and v-pot/fader readout to work. That leaves us with a supply need of +5V (current rating unknown) and +12V for the controls/motors (current rating within normal PC supply spec).
As I see, it would be probably possible to take a higher capaity PC PSU and to replace the BFC with an IEC mains connector, going to this PSU inside the d8b. +12V is currently provided by the PC style PSU, so the new PSU would no doubt be adequate for the job (even more so, because there's no load from the d8b CPU motherboard).
As to the +5V, even if the required current rating is too high with all circuits connected, you can probably disconnect the DSP, DCA and CODEC boards (plus all expansion boards) which would more than likely reduce current requirement to fall well within the rating of a regular PC PSU (DSP probably being the heaviest load, followed by CODEC and DCA).
So, if someone is really willing to go that way, I think that a single box 'controller' type d8b is quite feasible (some tinkering notwithstanding
).