RS 485 and devc-ser8250

QNX DEVELOPERS General Programming
1

Hi,

We have a custom serial card which has 4 serial ports one on which is a RS 485 port. I would like to know if i can use the serial port driver,devc-ser8250 for communication with this port ?? The documentation says it only supports the RS 232 standard.

regards,
QNXLYZER

2

485 needs a way to tell the serial card not to drive the tx line. That is usually done through CTS, signal.

devc-ser8250 will not take care of this for you. Either you customize the driver or you have some piece of hardware deal with this automaticaly.

It’s possible to do it outside of the driver (from your application) but the cost is speed.

3

Mario is right.

You can use the devc-ser8250 and do the RS485 specific stuff outside the driver. We did that already using a wrapper. Please look at the clock-speed of the chip and change the drivers ‘-c’ option accordingly.

Which silicon are you using for the serial communication ?

Freddy

4

Thanks for the replies, I got the serial card to work, we are using a 4 port serial card with an interrupt share, I had to modify the RJ 45 jack for the proper communication standard.

cheers !!,

QNXLYZER

5

Some cards allow the Tx data to control the tri-state on RS-485 links. We’re using CTi’s BlueStorm, that supports this option.

kmb