[uClinux-dev] Serial Port woes

Matthew Natalier matthewn at snapgear.com
Wed Mar 26 17:55:57 EST 2003


It sounds like it should be enough to run something like:

tip -8 -n -1 -c -s 57600 /dev/ttyS0

This is:

-8 - set data bits to 8
-n - set parity to none.
-1 - set stop bits to one.
-c - set clocal mode.
-s - speed

By default tip won't use any flow control.

If you are trying to connect to the device with an application, then tip
has good examples of setting up a serial port the way you want it and a
"man termios" on my Debian and on my RH 8.0 box reveal (almost) everything 
you can do with serial ports on a Linux system.



Daniel Ng wrote:
> Hi,
> I'm trying to communicate with a 3-pin RS232-based (only Tx, Rx and
> Common pins on the connector) serial device via the 9-pin RS232 port on
> my uClinux-based product (SnapGear SE1100).
> So far, I can connect the serial port on the SE1100 to a modem, and
> successfully communicate over that connection (via the 'tip' console
> program).
> However, when I plug the 3-pin serial device into the SE1100, I can't
> seem to be able to talk to the serial device at all (absolutely no
> response from the device). If I plug that device into a PC, I have no
> problems with talking to it.
> I've tried- 
> 1) Mucking around with the stty command(in particular setting clocal
> and -crtscts)
> 2) Shorting the DSR and DTR pins together, and having a (separate)
> short between the RTS and CTS pins 
> 3) Using different combinations of speed and different types of flow
> control, spacing, etc.
> 4) Putting a RS-232 tester box in series with the connection. LEDs on
> the box show which pins are active.
> 1,2,3 don't result in any difference in behaviour (ie. no response from
> the 3-pin device).
> Using 4, I found that when I connected the SE1100 to the modem, the CTS
> and DSR pins are active, but when I connect the SE1100 to the 3-pin
> device, none of the pins are active.
> Any ideas most welcome...
> Daniel.
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Matthew Natalier
Systems Programmer
p: +61 7 3435 2805
f: +61 7 3891 3630
matthewn at SnapGear.com
Custom Embedded Solutions
Security Appliances

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