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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" <bor@xxxxxxx.ua>
To: <dev-etrax@xxxxxxx.com>
Sent: den 6 december 2002 16:03
Subject: RS-485 port using on ETRAX LX and RS-485-to-RS232 converter by
Moxa...


>                 Hi!
>
>   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
A50
>   converter work perfect.
>
>   programm use /dev/ttyS3 device as serial device, set speed, baudrate,
parity..
>
>
>   can anyone comment this?  any solutions?
>
> --
> Bor.

Hi,
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.

Best regards
/Johan