Extcomm port for second RS485 on M503

Mohamed Dounnani

Hi I would like to know what extcomm port is for control second modbus rs485 port

I use extcomm/0/0 for the first port but there is extcomm/1 and extcomm/2 what is the correct port?

Martin Kudláček

Hi @mohamed-dounnani,
the addressing is as follows:

/dev/extcomm/0/... <- All serial ports (0 = RS485 1.1, 1 = RS485 2.1)
/dev/extcomm/1/... <- Serial ports of Group 1 (0 = RS485 1.1)
/dev/extcomm/2/... <- Serial ports of Group 2 (0 = RS485 2.1)

You can reveal the structure by listing the directory:

unipi@L503-sn101:~ $ ls -l /dev/extcomm/*
/dev/extcomm/0:
total 0
lrwxrwxrwx 1 root root 12 Aug 31 09:51 0 -> ../../ttyNS0
lrwxrwxrwx 1 root root 12 Aug 31 09:51 1 -> ../../ttyNS1

/dev/extcomm/1:
total 0
lrwxrwxrwx 1 root root 12 Aug 31 09:51 0 -> ../../ttyNS0

/dev/extcomm/2:
total 0
lrwxrwxrwx 1 root root 12 Aug 31 09:51 0 -> ../../ttyNS1

Martin