My Pi 3 is connected to a solar panel system with an USB to RS232 cable. Unfortunately I am unable to receive any data with the Pi so far. I got it working under Windows. What I've checked on my Pi so far:

1) My pi recognizes the device.

root@zonnepaneel:~# lsusb
Bus 001 Device 005: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port

2) The device is listed as ttyUSB1 and the rights should be sufficient.

root@zonnepaneel:~# dmesg | grep tty
[0.000820] console [tty1] enabled
[7221.626142] usb 1-1.2: pl2303 converter now attached to ttyUSB1

root@zonnepaneel:~# ls -l /dev/ttyUSB*
crw-rw-rw- 1 root tty 188, 1 feb 13 10:11 /dev/ttyUSB1

3) It can be connected with cu (baud rate 9600 is correct).

root@zonnepaneel:~# cu -l /dev/ttyUSB1 -s 9600 --parity=none

However, no data is displayed. What can I try to make this work?

  • Data is line buffered in the terminal. Does the solar panel system ever send \n?
    – Janka
    Commented Feb 13, 2018 at 10:26
  • And you have tried to switch Tx and Rx?
    – MatsK
    Commented Feb 13, 2018 at 11:14
  • No, I don't think the system sends an \n. Is there another way for me to check wheter I receive data @Janka? And, @MatsK can you explain where I can do that?
    – Leon
    Commented Feb 13, 2018 at 12:57

1 Answer 1


To check if you had problems with the cu program, try

# stty -F/dev/ttyUSB1 speed 9600
# od -Ax -tx1 /dev/ttyUSB1
  • The first line prints 9600. The second gives a blank result.
    – Leon
    Commented Feb 13, 2018 at 13:35
  • Then, there's no data received. Maybe you need to trigger the device first?
    – Janka
    Commented Feb 13, 2018 at 15:01
  • Yep that was the solution. It turned out that there was some kind of handshaking needed. For those in need: I managed to connect by making use of this script: github.com/trollkarlen/inverter_monitor/blob/master/README.txt
    – Leon
    Commented Feb 19, 2018 at 14:01

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