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Modbus slave problem
Willie from South Africa [4 posts] |
1 month
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Buy the Blackfin Camera Module from Trossen Robotics |
Hi Steven,
I have been testing the Modbus slave functionality and there seems to be a bug in the works. When I use a Modbus master to read variables (mapped to holding registers which by definition are read/write) from RR everything works as it should. I have declared a dummy variable which I am trying to modify from the Modbus master. RR then states that a Input Register (by def. Read only) has been written but the variable is left unchanged. I have tried different MB masters all with the same result although some display exception errors on receipt of the response to the write request (Modbus request 16). I normally use Modscan as a testing master. I have attached the .robo file. If I write multiple coils all coils accept the change, except for the coil that are linked to the variable mb_trig . (MBcoil.robo)
 program.robo
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Steven Gentner from United States [2177 posts] |
1 month
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Willie,
Thanks for such great information and debugging! It indeed looks like the FC_PRESET_MULTIPLE_REGISTERS function was incorrectly updating input registers as the log was indicating. As your variable is mapped to a holding register nothing was getting updated. We corrected this to now update the holding register instead of an input register. Note that this also affected the FC_PRESET_READ_MULTIPLE_REGISTERS function that was also pointing incorrectly to input registers.
Please download 2.5.5 for that fix and let us know if it does the job!
Thanks,
STeven.
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