The parameters such as port, baudrate, bytesize,parity,and stopbits were set correctly, but it always returns this: 19:24:34,282 INFO modbus_rtu._init_ MainThread RtuMaster /dev/ttyUSB0 is opened Logger.error("%s- Code=%d" % (e, e.get_exception_code())) (master.execute(1, cst.READ_HOLDING_REGISTERS, 0, 49)) t_verbose(True) #print some more log prints for debug purpose t_timeout(5.0) #Change the timeout value/Defines a timeout on the MAC layer Master = modbus_rtu.RtuMaster(serial.Serial(port="/dev/ttyUSB0", baudrate=9600, bytesize=8, parity='N', stopbits=1, xonxoff=0)) Logger = modbus_tk.utils.create_logger("console") #add logging capability import logging import modbus_tk import modbus_tk.defines as cst import modbus_tk.modbus_rtu as modbus_rtu When I use modbus_tk 0.5.7 and run the following code： import sys import serial I have tried the modbus_tk 0.5.7 and MinimalModbus to implement the communication under Modbus-RTU protocol. I used a RS232/USB adapter and a RS485/RS232 adapter to link the meter and the USB port on the Raspberry Pi. In this case, the error appeared on a Linux when trying to upload code due to the drivers not being installed and the root permissions.I am trying to use a Raspberry Pi 3B (run Ubuntu Mate 16.04 operating system)as a Master to read values from an electric energy meter which supports Modbus-RTU protocol. language:bashĪvrdude: ser_open(): can't open device "/dev/ttyUSB0": No such file or directory You may receive an avrdude: ser_open(): can't open device error similar to the output shown below. If you installed the drivers for the CH340 on your computer but have issues connecting via serial terminal or uploading code using the Arduino IDE, there may be an issue with your user settings preventing you from using the CH340. COM Port Not Available Windows, Mac, and Linux Users seem to be able to eventually get the board recognized by a combination of giving the computer time to finish the install ( close to 20 min), plugging the board back in multiple times, reinstalling the drivers, and/or resetting the computer multiple times ( repeat both steps). Others have had issues where the installation process hangs.īased on the customer experiences, this might be specific to the manufacturer and are usually isolated cases. However, the board cannot be accessed on the Arduino IDE. We have had a few reports on Windows 10 where the driver will automatically install and the board will show up under a new COM port as USB-Serial CH340, but with a different device name. Troubleshooting COM Port is Not Showing Up as CH340 Windows
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