Error in API description for Modbus Server - write to hold register

[Sonnengruesser]

I need to set up a modbus server that provides a defined set of data to an existing modbus master.
The modbus master sends regular "read holding registers" requests. So I'm trying to set up a Modbus server with holding registers to provide this data.

The docu says "Write Single Holding Register" function performs a write action on the bus, so not what I need.

I couldn't find a function to insert data into the holding registers for the client to read. What am I missing?

[per1234]

Hi @Sonnengruesser. Thanks for your interest in this open source project. This issue tracker is only to be used to report bugs or feature requests specific to the project. This topic is more appropriate for the Arduino Forum. I'm sure we will be able to help you out over there:

https://forum.arduino.cc/

[Sonnengruesser]

@per1234 I figured it out myself - there is actually an error in your API description.

The API description for modbus server says that "holding register write" function has to variants - with or without ID as parameter - but is basically the same.
This is true for the client functions, but is wrong on Modbus server.

On modbus server if you specify the ID (3 parameter inputs) the function will perform a "holding register write" on the bus.
On modbus server if you use the 2 parameter input function, the function will write the value to its internal holding register.

API documentation here:
https://github.com/arduino-libraries/ArduinoModbus/blob/master/docs/api.md#modbusserverholdingregisterwrite
Header-file here:

ArduinoModbus/src/ModbusServer.h

Line 78 in 581a61f

int holdingRegisterWrite(int address, uint16_t value);