I am using a RS485 to USB converter to convert and pymodbus/Qmodbus to read modbus data but the data cannot be read with the same converter in Jetson alone. But it works flawless in my PC and Other Setups.
FYI: I have read forum posts closed with reference saying conversion will not be handled by jetson. We dont expect to. I use a external module to convert from rs485 to usb. Yet it doesnt work in Jetson alone.
This problem is more an Ubuntu/linux issue than a Jetson particular problem. First thing to do is to verify whether your system is detecting the new USB converter or not. To do that I would disconnect the USB converter and reboot the Jetson, once it rebooted check under the /dev/ folder and check the tty devices, after that plug the USB converter and verify whether the device is detected, a new tty device should show up in the /dev folder. The name could be something like: /dev/ttyUSB0 or something like that, the point is that it wasn’t there before connecting it.
If a new device shows up it means that linux was able to detect it and that would mean that there is principle no hardware/driver issues, if it doesn’t show up it means that a new driver is required and you will need to get that from the USB converter maker website. See this for instance for related info: c - USB to RS485 converter on Linux - Electrical Engineering Stack Exchange and this: https://techsparx.com/energy-system/modbus/linux-modbus-usb-rs485.html
After that you need to test the device, you need to wire the devices that you will be communicating to, to the RS485 converter side and set up pymodbus (or whatever library or tool you are using) with the right settings e.g. name of serial port (/dev/ttyUSD0 or similar), baudrate. parity, stop bit and data bits. That information is given by the device that you are trying to communicate to through the converter see the serial section of this: Pymodbus REPL — PyModbus 3.0.0.dev5 documentation
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