Messages in this thread |  | | | Date | Thu, 11 Nov 1999 13:19:42 -0500 | | From | "Theodore Y. Ts'o" <> | | Subject | Re: Need info about serial port programming -UPDATE |
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Date: Thu, 11 Nov 1999 18:24:34 +0100 From: Jens Benecke <jens@pinguin.conetix.de>
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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