Issue specifying <object_type>+<start_address>

[digispiders]

Unless Im missing something, here is whats happening:
When preparing the config file, it appears that its pulling an offset in the modbus addresses from the object type, and adding the starting_address value to it. So, if you specify:

poll,holding_register,40001,10,BE_BE
ref,objectname,40001,uint16,r

It throws an error. It appears that it might be adding 40001 from the type=holding_register to the specified address (40001) to be polling at the wrong place.
If you specify:

poll,holding_register,1,10,BE_BE
ref,objectname,1,uint16,r

It pulls from 40001 (the first holding_register).

Problem:
This conflicts with the documentation: helloysd

Suggested Resolution:
Should either pull offset from object_type and be documented as such, or ignore type and only pull from specified start_address.

Uploading config files and screen shots to demonstrate.

[gavinying]

@digispiders Firstly, congratulate you have actually retrieved data according to your last screenshot.

As you mentioned, instead of polling start from the standard holding_register address 40001,

poll,holding_register,40001,10,BE_BE
ref,objectname,40001,uint16,r

you end up with polling start from address 1,

poll,holding_register,1,10,BE_BE
ref,objectname,1,uint16,r

This happens quite often because Modbus is an open protocol, different vendors have their own interpretation on the standard, that's why we have many different variants, e.g. zero-based vs one-based, big-endian vs small-endian, etc. Usually vendors will provide documents/examples to help developers for integration.

In your case, your device vendor is using relative address (offset address) rather than absolute address for data comm.

Hope that helps for clarification.

[digispiders]

Okay. It was a little unclear to me based on the documentation in modpoll + what the manufacturer put out, in combination with my poor understanding of modbus addresses. I assumed that an address was an address, and if an 'offset' to an 'address' was specified (e.g. 1 to 40001), I should call the address (40002) which was probably wrong to assume. Feel to close.