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Re: RS-485 port using on ETRAX LX and RS-485-to-RS232 converter by Moxa...
----- Original Message -----
From: "Vladimir Bormotov" <email@example.com>
Sent: den 6 december 2002 16:03
Subject: RS-485 port using on ETRAX LX and RS-485-to-RS232 converter by
> We have some troubles with connection rs-232 device via Moxa A52 Smart
> Converter to devboard's rs485 port. Programm inside DevBoard can't get
> valid data from rs-232 device, behinde conerter. In other side, Moxa
> converter work perfect.
> programm use /dev/ttyS3 device as serial device, set speed, baudrate,
> can anyone comment this? any solutions?
I assume you are using 2-wire RS-485.
Are you controlling the RTS signal from the DevBoard program manually
or using the RS-485 ioctl() to configure RS-485 (TIOCSERSETRS485)
and write RS-485 data using the TIOCSERWRRS485 ioctl()?
The RTS signal controls the direction of the RS-485 line
so you must do something with it.
You must use kernel 2.4.19 with the patches from
http://developer.axis.com/download/linux/ for RS-485 to work.
For 2-wire RS-485 it is the RX pins that should be used,
they can switch direction (with RTS), but the TX pins are always transmit.