RS-485 Shield for Raspberry Pi

Products & Technology Raspberry Pi
#1

I installed a RS-485 Shield for Raspberry Pi on a new raspberry Pi4, ran sudo raspi-config, selected “3” interface options, selected P6 serial port, disabled shell, enabled serial port hardware.
I goto into node-red on the pi and am using the node-red-contrib-modbus “modbus read node” and it now finds dev/ttyS0 which I believe is the 485 shield.
I keep getting “TransactionTimedOutError: Timed out” & ““Modbus Failure On State sending Get More About It By Logging”” errors.
I know my slave settings (baud, data bit, stop bit, parity) are good as I have another modbus master which which works fine with this slave.

any helpful ideas?

thank you in advance.

#2

I think you need to test whether the serial port of RPI is set correctly first.

#3

Thank you Baozhu.
aside from that any else you can think of?

appreciate it!