Modbus Max-Device-ID too low for devices with high IDs

[muenchris]

Library/API/IoT binding

Modbus

Visual Studio version

VS2022.17.4

.NET nanoFramework extension version

No response

Target name(s)

ALL

Firmware version

N/A

Device capabilities

No response

Description

There are devices out there (i.e. https://www.amazon.com/dp/B07ZYVZZKK?ref=ppx_yo2ov_dt_b_fed_asin_title - See section #3 "Read device ID") that use a high ID during calibration or readout of their real ID.

    /// <summary>
    /// The highest accepted device id on RTU protocol.
    /// </summary>
    public const byte MaxDeviceId = 0xF7; // 247 

This number needs to be increased to 255 to be able to read these parameters off these devices

How to reproduce

Try to access any device with a system parameter device ID larger than 247 like
https://www.amazon.com/dp/B07ZYVZZKK?ref=ppx_yo2ov_dt_b_fed_asin_title

Expected behaviour

Should be possible somehow. Maybe with a special call that allows to address these high numbers

Screenshots

No response

Sample project or code

No response

Aditional information

No response

[josesimoes]

Did you made any investigations on how this is being handled on other open-source Modbus libraries?

[muenchris]

I have tested this with other free Modbus testing tools like: https://www.modbustester.com/#download
they do accept higher IDs.
On the desktop I am using https://github.com/NModbus/NModbus and it does not do any checks on the slave address allowing even 255 as a valid address.