fallenman
commented
7 years ago Thank csardopt for posting this error and thank karlp for fixing it. At first, I tried karlp's code but somehow the problem was still there. With karlp's definition of this new error, I found another cause. Since arduino 1.0, Serial.flush() is repurposed to waiting for ongoing data sent complete rather than dropping received data. I changed Serial.flush() to Serial.read() and slightly modify the loop in flush() function and get arduino work. However, my arduino still has a small chance to respond this error while my other non-arduino modbus devices don't, but the chance now is acceptable.
If you have a network with more than one slave there will be wrong responses (exception responses that shouldn't be done). Supose that master makes a query to slave 1, then slave 2 sees the answer and sends "something", that I suppose is "response_exception". The same applies to other slaves... more slaves more mess...
Basic solution: eliminate or comment the answer "response_exception" in Modbusino.cpp, line 191 and line 214. Better solution: Make a better analyse of the frame to see it's not a answer from other slave... Hope this will be corrected because it's an nice modbus library for Arduino.