Nov-10-2020, 09:51 AM
Hey. I am working with raspberry PI and modbus. Raspberry PI is configured as master and I have multiple ESP32 devices configured as slave devices.
I am not entirely sure how modbus-tk library works but everytime I write to register or read from slaves, the raspberry PI is waiting for a valid response. If the response is invalid ( slave did not respond or its turned OFF), the python will throw me an error code:
My question is to how to properly handle this invalid response? For example If I want to do some task which involve 2 ESP32 slave devices I would use this command to initiate a task:
Also, same thing happens when I send "restart" command to any of my ESP32 slaves. When ESP32 receives the command, it restarts but I get the same error message on my raspberry PI ( My guess is that ESP32 device did not respond to the valid raspberry PI message before restarting).
Can someone suggest me a way to handle that?
I am not entirely sure how modbus-tk library works but everytime I write to register or read from slaves, the raspberry PI is waiting for a valid response. If the response is invalid ( slave did not respond or its turned OFF), the python will throw me an error code:
Exception in Tkinter callback Traceback (most recent call last): File "/usr/lib/python3.7/tkinter/__init__.py", line 1705, in __call__ return self.func(*args) File "/usr/lib/python3.7/tkinter/__init__.py", line 749, in callit func(*args) File "/home/pi/Desktop/lukas_programming/PTL_python/PTL_Modbus2.py", line 464, in <lambda> master.after(100,lambda:update_current_operation(myConnection)) File "/home/pi/Desktop/lukas_programming/PTL_python/PTL_Modbus2.py", line 508, in update_current_operation master_modbus.execute(int(Device), cst.WRITE_SINGLE_REGISTER, 24, output_value=Quantity) File "/home/pi/.local/lib/python3.7/site-packages/modbus_tk/utils.py", line 39, in new raise excpt File "/home/pi/.local/lib/python3.7/site-packages/modbus_tk/utils.py", line 37, in new ret = fcn(*args, **kwargs) File "/home/pi/.local/lib/python3.7/site-packages/modbus_tk/modbus.py", line 306, in execute response_pdu = query.parse_response(response) File "/home/pi/.local/lib/python3.7/site-packages/modbus_tk/modbus_rtu.py", line 46, in parse_response raise ModbusInvalidResponseError("Response length is invalid {0}".format(len(response))) modbus_tk.exceptions.ModbusInvalidResponseError: Response length is invalid 0https://ibb.co/TM1Vp5f
My question is to how to properly handle this invalid response? For example If I want to do some task which involve 2 ESP32 slave devices I would use this command to initiate a task:
for Device,Quantity,Serial in cur.fetchall() : device_list.append(Device) Priority = Assign_priorities(Serial) item.append([Device, Quantity, Serial, Priority]) counter=counter+1 master_modbus.execute(int(Device), cst.WRITE_SINGLE_REGISTER, 24, output_value=Quantity)This will write to register 24 for both devices, if both devices are working properly, everything will be fine, however,if one of the devices are OFF or not working, I need to be able to know and handle it appropriately(notify user to turn ON the required device for example or something)
Also, same thing happens when I send "restart" command to any of my ESP32 slaves. When ESP32 receives the command, it restarts but I get the same error message on my raspberry PI ( My guess is that ESP32 device did not respond to the valid raspberry PI message before restarting).
Can someone suggest me a way to handle that?