Steven Zins wrote at 08/21/2011 11:53 PM:
How do I set baud/parity/stop in Racket for a serial port in
Windows/Linux/Mac. Eg for "\\.\COM4"
I bet you're going to need to make some Windows system calls using the
Racket FFI. I don't know what the best documentation is for the Windows
calls, but Google found these:
http://www.robbayer.com/files/serial-win.pdf
http://www.codeproject.com/KB/system/serial_com.aspx
Hopefully you can use Racket ports. If you can, you'll probably want to
make sure buffering is disabled ("file-stream-buffer-mode"). Then
you'll probably either want to use "sync" or separate threads to avoid
blocking your entire program on port I/O.
If you happen to be new to RS232, and talking with your device doesn't
work the first time, and reliably, you're in for a treat, because this
stuff is ancient. (Ancient, like, one printer I owned, the user manual
told you to open up the printer housing and cut a trace on the circuit
board, depending on whether you wanted RS232 or current loop, apparently
in a time when what would be an ordinary thing for a user to do.) If
you don't know exactly what parameters the device you're talking with
wants, I think a fairly conservative first-guess is 9600/8/N/1. If that
doesn't work, I'd try 7/E/1. Then, going back and adjusting the baud
(look up online what typical baud rates are). If doing terminal
communications, characters sent by the terminal may or may not get
echoed back (look up "duplex"). You might also have to deal with Ctrl-S
/ Ctrl-Q flow-control (perhaps only not sending it, or perhaps using
and/or handling it), and with NULs. Hopefully you don't have to deal
directly with the UART like we did in the '80s, but you *could* do that
from Racket with the FFI if you had to. (I'm not quite that old;
anything else I knew about RS232 was forgotten once I hit puberty.) If
you happen to actually be using USB, and this old COM-port stuff (RS232)
doesn't work completely for your device, then you might need to make
USB-specific calls. That, and your towel, will prepare you for any
eventuality.
--
http://www.neilvandyke.org/
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