CODEWITHSUNDEEP
linuxterminalraspbiantty
Sundypha
Sundypha

Reputation: 35

write and read from ttyUSB0, can't get response

I'm not very experienced with the Linux tty's. My environment is a Raspbian with a prolific USB-serial.

What works:

stty -F /dev/ttyUSB0 38400
cu -l /dev/ttyUSB0 -s 38400

cu to /dev/ttyUSB0 works. I can write my commands to the terminal and get response from the other terminal within 300ms.

What not works: in one terminal

echo "command" > /dev/ttyUSB0

in another terminal (running before echo)

cat < /dev/ttyUSB0

or

tail -f /dev/ttyUSB0

there is no output.

But when i echo "command" > /dev/ttyUSB0 and have cu open, I can see the echoed command and the response from the other terminal there.

What am I missing?

best regards

Sundypha

ps: What I tried too, was a little python script:

#!/usr/bin/python
import serial
ser = serial.Serial('/dev/ttyUSB0', 38400, xonxoff=True)
ser.open()
if ser.isOpen():
    ser.write('command')
    response = ser.readline()
    print response
    ser.close()

did not work either, hangs on ser.readline()

Upvotes: 3

Views: 12897

Answers (1)

Klaatu von Schlacker
Klaatu von Schlacker

Reputation: 210

If you are not cat'ing the USB0 device as you echo to it, then yes, you will not see its output because it has been and gone.

try something like:

tail -f /dev/ttyUSB0

and then echo stuff into it.

Upvotes: 0

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