The idea is that the onboard peripherals would be driven by a VERY simple OS, which would basically just be a simple request/response type system. IE. send a command, read the result back, or send a command, then receive a data stream until further notice. The RTC could be set to send a time update every second, for instance.

At least one of the ADCs will have a preamp on, yes.

The 12V IO would be done in a robost manner. Outputs would be via the same sort of solid-state switch that the auxilary output on the empeg already uses, which is pretty bomb-proof anyway. Resettable fuses are a possibility, but they're a bit expensive. Relays are much too expensive.

Opto-isolated TTL I/O is, again, possible but adds to the price. A cheaper solution is a socketed, sacrificial buffer, and common sense.

The control stalk interface is subject to variation, since I'd need to get several different ones and try them. They're likely to be either a simple serial protocol, variable resistors, or switches, so the standard interfaces on the proposed board would handle them anyway.

The main serial port to the empeg would be normal RS232 line levels. There is only one hardware UART on the 16C77, but software ones could easily be implemented as long as the baud rate wasn't excessive. The processor would be run at around 20MHz, so it would handle up to, say 4800 baud for GPS systems, without much trouble.

Ram is more of a problem. The internal RAM of the 16C77 is limited, and for cost/simplicity reasons I'd like to stay with a single-chip solution. It would be possible to add an external static ram chip, but this would eat up about 20 of the 33 available IO lines.

I'm planning on using a standard eurocard (160mm x 100mm) board size, which would fit dozens of standard boxes, some of which are very nice even though quite cheap.

Patrick.


Opinions expressed in this email may contain up to 42% water by weight, and are mine. All mine.