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Description

Questions and comments about
Gurux DLMS/COSEM for Python Protocol Component.

By Kumaresh , 24 August, 2026

DLMS Image Transfer: “byte must be in range(0, 256)” with 512-byte block size in Python

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Gurux DLMS for Python

Hi Gurux Team,

I am facing an issue with FOTA Image Block Transfer in Gurux.DLMS Python.

The same meter and firmware FOTA work correctly using DLMS Director, but when I perform the same operation using the Python implementation, Image Transfer Initiate succeeds and Image Block Transfer fails with:

   byte must be in range(0, 256)

The meter reports:

   Image Block Size : 512 bytes
   Image Transfer Enabled : True

Image Transfer Initiate (Method 1) is successful.

Gurux DLMS for Python