Communication problem in Modbus RTU

[rickypid]

I tried to establish Modbus RTU communication between Arduino Portenta Machine Control and a device, but without success.

I wanted to follow the example given here to the letter:

https://docs.arduino.cc/tutorials/portenta-machine-control/user-manual/#modbus-rtu

I discovered that this line of the tutorial's code:

MachineControl_RS485Comm.begin(baudrate, preDelay, postDelay);

had not been updated to reflect the change made by #27.

I added the missing the config argument:

MachineControl_RS485Comm.begin(baudrate, SERIAL_8N1, preDelay, postDelay);

I submitted a correction for the tutorial: arduino/docs-content#2779

I ran the tests in both half and full duplex without success. Even with the correction, the problem persists. This is the error:

- Writing coil values ... - Failed! Error code: Connection timed out
- Writing coil values ... - Failed! Error code: Connection timed out
- Writing coil values ... - Failed! Error code: Connection timed out
- Writing coil values ... - Failed! Error code: Connection timed out

I don't understand where the problem lies. We have purchased many Portenta Machine Controls for this purpose, so if it does not work, we need to figure out how to solve the problem.

This is my PlatformIO ini file:

[env:portenta_h7_m7]
platform = ststm32@~19.4.0
board = portenta_h7_m7
framework = arduino
build_flags = -Os -flto
lib_deps = 
	arduino-libraries/ArduinoBLE@^1.4.1
	bblanchon/ArduinoJson@^7.4.2
	arduino-libraries/ArduinoRS485@^1.1.1
	arduino-libraries/Arduino_PortentaMachineControl@^1.0.4
	arduino-libraries/ArduinoMqttClient@^0.1.8
	mobizt/ESP_SSLClient@^2.2.3
	arduino-libraries/ArduinoModbus@^1.0.9

Additional context

Related discussion:

https://forum.arduino.cc/t/arduinomodbus-rs485-with-portenta-machine-control-basic-guide-updated-for-the-new-arduino-portentamachinecontrol-library/1030490/18

[leonardocavagnis]

Hi, thanks a lot for the report
To help us debug this, could you try running the same example using Arduino IDE 2.x instead of PlatformIO and let us know if you see the same timeout issue?
Thanks!

[rickypid]

Hi @leonardocavagnis,

I will run the requested test this evening and get back to you with feedback! I hope to resolve this as it is a significant limitation for the client's project!