The hardware expects a clock signal on the DTR pin (whenever DTR is toggled
it sends a bit), a fixed configuration signal (bit width, LSB/MSB conf,
etc) on the RTS pin, and sends the binary data on the DTR port. They
designed it so that "it's easy to program from DOS" (which is probably even
true), but I would like the machine to run under Linux, because it has to
put the gained data over a network.
The sampling frequency with which the DTR is being fed is way below a kHz,
so my former ideas about 4..5kHz sampling frequency seemed to have failed
on the hardware (the A/D chip is a cheap one, it seems).
Even if you're onlysampling at a rate of ~500 Hz or so, you probably
want to do this using RT Linux, using a kernel module, and hitting the
UART directly. Recall that the system clock on an i386 is 100Hz, and so
doing this in user mode won't work well at all. I'd suggest using RT
Linux, which will give you the scheduling guarantees you need, and since
RT Linux tasks are implemented in kernel mode, you can mess with the
UART bits directly.
- Ted
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