How do you know which hardware serial port ModbusClient uses (e.g., Serial3 on STM32Duino)?

[SeppeBudenaers]

Hi everyone,

I'm working on a project using an STM32 running STM32Duino, and I want to use the ModbusClient library. Is there a way to configure it to use a specific hardware serial port, like Serial3?

I came across this example:

But as far as I can tell, it doesn't let me specify which serial port to use.
Am I missing something, or is there a way to set a different hardware serial?

Thanks in advance!

[drondistortion]

:tumbleweed:

tldr: don't use this library, use https://github.com/CIRCUITSTATE/CSE_ArduinoRS485 and https://github.com/CIRCUITSTATE/CSE_ModbusRTU - it explicitly says that it is for ESPs and STMs. Examples there are much more explicit...

original message:
both constructor and begin function take a reference to a RS485Class as a parameter. So you need to explicitly create an instance of RS485Class with said Serial and then pass it for example in the begin like so modbusRTUClient.begin(myRS485, boudrate, config)
ArduinoRS485 specifies constructor like so: RS485Class(HardwareSerial& hwSerial, int txPin, int dePin, int rePin);
Why it needs txPin for HardwareSerial is beyond me...

Example:

#define myDEPin 3
#include "ArduinoRS485.h" 
#include "ArduinoModbus.h"

myRS485(Serial3, -1, myDEPin, -1); // would probably work, if don't - specify txPin and rePin

then create ModbusRTUClientClass, or pass myRS485 into begin function:

ModbusRTUClientClass myModbus(myRS485);
/* ... */
// in setup:
myModbus.begin(115200);

or

// in setup:
myModbus.begin(myRS485, 115200);