We have developed a working GUI of our own and can read all the registers no problem...that's why this new problem is confusing me so much. Surely they haven't changed the way the registere are addressed between reading and writing. I've got a contact within the company so shall give him a ring to confirm this though.
They do have software of there own however it doesn't communicate using the modbus protocol.
As for the register you can write to, you are correct, there are only a few of them that can be changed.
When we read values back from the device, we had to combine two 16-bit registers together and convert them from single precision to get any meaningful values. Using this logic then, we have to sent across two 16-bit numbers (one being all zeros), which both share the same starting address. This is coherent with the format that came back when we read the registers, the first register came back as all zeros and the second one contained a number. When combined, they provided useful info.
Thanks
Gordon
