MEGA-BAS RS485 Rpi passthrough

[orrious]

I made the leap today from my own hardware to REM with MEGA-BAS . The only thing I wasn't able to test prior to switching was RS-485 and now having problems with getting it working from RPi through the MEGA-BAS.

I've disabled bluetooth and logins on all the RPi UARTS. I'm not able to see any traffic on the serial ports when I screen /dev/ttyAMA0 9600 or screen /dev/ttyS0

Jumpers are correct on the MEGA-BAS and in REM I have the RS485 port in passthrough

What am I missing?

[tagyoureit]

Make sure that your serial port is enabled and the serial console is disabled. https://github.com/rstrouse/relayEquipmentManager/wiki/Sequent-Microsystems-Boards#rs-485-tab

It should start being chatty on /dev/ttyS0.

[orrious]

I followed these to setup it up. Still no joy. I've installed my old USB-RS485 adapter and have it working that way for now. I also left the MEGA-BAS RS485 on it as well so I could sniff traffic live traffic.

That said, I'm unable to open /dev/ttyS0. It baffles me as I've turned off bluetooth, disabled serial login, enabled the serial port, etc.

/dev/ttyAMA0 does see traffic, but it's garbled. On the MEGA-BAS, do you know which pin is High or Low?

[tagyoureit]

Check from the command line. You can install the mega-bas command line tools.

When you run the following command the important part is that mode=0. That is rs485 passthrough. The speed settings you see relate to mode=1 which is modbus.

pi@nixie:~ $ megabas 0 rs485rd
<mode> <baudrate> <stopbits> <parity> <add> 0 38400 1 0 1

/dev/ttyAMA0 is for the video display ports and not applicable. Just ignore them for this application.

[orrious]

<mode> <baudrate> <stopbits> <parity> <add> 0 38400 1 0 1

This looks good to me. So megabas is in passthrough.

When it stops raining, I'll take a USB UART out and connect directly to pins 8 and 10 on the RPi header.

[orrious]

For whatever reason the serial port I have to use is /dev/ttyAMA0. I have it working though through the MEGA-BAS

[tagyoureit]

It looks like it depends on the hw. RPi3 on /dev/ttyAMA0 is /dev/ttyS0 on RPi4. https://raspberrypi.stackexchange.com/questions/45570/how-do-i-make-serial-work-on-the-raspberry-pi3-pizerow-pi4-or-later-models/45571#45571

[orrious]

I completely forgot about this command and is what helped diagnose.

od -x < /dev/ttyAMA0 and od -x < /dev/ttyS0