Shevek (shevek) wrote,
Shevek
shevek

I bought some nice computerised toys on eBay. I did quite nicely. I got a CD player, a zone mixer and a funny VCA box. I am now trying to sell same for more than I bought them for.

I'm hunting for the specs for the Databeat VCA 4/1 SM. It seems to be a 4-stereo pair RS232 controlled mixer. I need to know the RS232 protocol for controlling it. It's based on a set of VCAs controlled by a Mitsubishi M37451SSP MCU. Mitsubishi sold their entire MCU concern to a company called Renesas, but while the Renesas web site talks a lot about 8 bit MCUs, even specifically the 740/7450 series, the 37451 has been obsoleted by the 7540 series and the datasheets from the old series were not transferred from Mitsubishi. I got some of the old programmers' manuals from http://www.archive.org/ but I cannot find the pinout or memory/SFR layout for a 64 pin DIL M37451.

On the other hand, the MCU is hooked up to an EPROM. (Apparently with separate address/data lines? The only chip near it is a 74HCT04, which isn't an address latch, and it's not like the MCU is short of pins.) So given the opcode table for the MCU (which I have), I should be able to read the EPROM and guess from the code what the SFR layout is, at least sufficiently to work out the RS232 coding on the input and write some software to control the device. My other random thought would be to replace the MCU entirely with a PIC 16F877-20 in a header, and write my own logic inside the mixer itself. I would rather not do that. It isn't worth it to me.

Did I say, I'm not actually an electrical engineer. Nonengineering approaches I am considering include hooking up a different function generator to each of the 8 inputs and sending random bytes down the RS232 port, then watching the output on a scope (with 47K across the output XLRs). The motherboard does have some status LEDs on it which might be useful. I don't generally like the "hope to get lucky" approaches. Also, I only have a 1-channel function generator, and it's a kludge.

The zone mixer is a Cloud CX132. I have no idea what I'm going to do with this. I guess I have a slim chance of using zones on the mixer auxes at home. It's in perfect condition, but apparently unless anyone actually wants a zone mixer, I'm stuck with it. It's a very specialist piece of kit. At least it's only 1U high.

The CD player is a Denon DN-1400F. I mentioned to someone that I had a CD player weighing 20Kg, and he said, "That's one hell of a CD player." He was right. I was actually trying to buy a set of 2500 or 2600 decks, but I saw this, so I bought it. It's a dual-deck 200 CD changer with RS232 remote control, and unlike Databeat, Denon do publish the specs for the serial protocol so I can knock up a controller in a few minutes. I will check it out (it had a minor fault preventing power-on which I have diagnosed and will fix tomorrow) and sell it back into the trade; I should make enough to go out and buy a really nice set of decks. (Does the jog shuttle on the CMX3000 allow you to tweak the offsets like the fine shuttle on a DN-1800? I can never quite use the pitch buttons on the DN-2000, I like wheels.)
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