Can't open serial connection in Pyserial: "termios.error: (22, 'Invalid argument') "

Question

I'm having problem executing the following code:

import serial

ser = serial.Serial(
    port='/dev/tty.FireFly-16CB-SPP',
    baudrate=115200,
    #parity=serial.PARITY_ODD,
    stopbits=serial.STOPBITS_ONE,
    bytesize=serial.EIGHTBITS
)

ser.open()
ser.isOpen()

This worked yesterday, and I don't know what I changed. Now I get the following error message:

    Traceback (most recent call last):
  File "main.py", line 32, in <module>
    bytesize=serial.EIGHTBITS
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/serial/serialutil.py", line 260, in __init__
    self.open()
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/serial/serialposix.py", line 280, in open
    self._reconfigurePort()
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/serial/serialposix.py", line 409, in _reconfigurePort
    termios.tcsetattr(self.fd, TERMIOS.TCSANOW, [iflag, oflag, cflag, lflag, ispeed, ospeed, cc])
termios.error: (22, 'Invalid argument')

I'm a complete beginner to Python, and can't decipher the error message above. I've tried reinstalling Pyserial, but that didn't fix the error. What is wrong?

score 3 · Answer 1 · answered Mar 17 '17 at 20:41

3

I had the same issue, though I was using a 5 port USB hub with 3 different USBs all plugged into it, and it turned out the hub wasn't providing enough power. Once I got an externally powered USB (one that wasn't just pulling off the line from my computer's port) it worked just fine.

answered Mar 17 '17 at 20:41

clifgray

4,313
11
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Same here. Errors on a hub, plugged directly into the back of the Mac problem went away. The port name changed too. – marxy Aug 28 '22 at 07:46
Similar problem with a USB hub, unplugging and replugging into the same hub helped. – 101 Jan 16 '23 at 23:10

score 0 · Answer 2 · answered Oct 12 '13 at 19:46

0

I had this problem on OSX, and the problem ended up being the baud rate was not supported. Changed the baud rate to something more common and it worked!

answered Oct 12 '13 at 19:46

zingle-dingle

1,681
16
16

score 0 · Answer 3 · answered Mar 31 '11 at 06:53

0

Is the port still there? I meen /dev/tty.FireFly-16CB-SPP. It could have a new name today...

answered Mar 31 '11 at 06:53

Daren Thomas

67,947
40
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200

Yes, from looking in /dev/ I see that the port is still there. – user685206 Mar 31 '11 at 07:08
1

It may also be worth trying the old 'turn it off and on again' - i.e. unplug the USB and plug it back in. This solved it in my case. – jsaven May 27 '17 at 09:57

P2bM · Answer 4 · 2011-03-31T09:16:56.953

0

Try this :

ser = serial.Serial('/dev/tty.FireFly-16CB-SPP',115200)
print "port is open" if ser.isOpen() else "port is closed"

you dont have to call open() unless you changed the configuration of the port manually eg:

ser = serial.Serial()
ser.baudrate = 19200
ser.port = 0
ser.open()

and don't forget to cles the port when you are done with it

edited Mar 31 '11 at 09:16

answered Mar 31 '11 at 07:46

P2bM

1,038
6
9

score 0 · Answer 5 · answered Mar 31 '11 at 11:01

0

Reinstalled Python and downgraded to 2.6 which solved everything.

answered Mar 31 '11 at 11:01

user685206

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score 0 · Answer 6 · edited Dec 12 '11 at 07:43

I have the same problem.

Just run the miniterm.py from pySerial examples (http://sourceforge.net/projects/pyserial/develop) .

It ran fine from shell: python miniterm -p ttyUSB0 -D but when tried to load it into Eclipse. and run debug from there. it gave me:

pydev debugger: starting
Traceback (most recent call last):
  File "/eclipse/plugins/org.python.pydev.debug_2.0.0.2011040403/pysrc/pydevd.py", line 1134, in <module>
    debugger.run(setup['file'], None, None)
  File "/eclipse/plugins/org.python.pydev.debug_2.0.0.2011040403/pysrc/pydevd.py", line 918, in run
    pydev_imports.execfile(file, globals, locals) #execute the script
  File "/root/workspace/pyserial/src/examples/miniterm.py", line 120, in <module>
    console.setup()
  File "/root/workspace/pyserial/src/examples/miniterm.py", line 101, in setup
    self.old = termios.tcgetattr(self.fd)
termios.error: (22, 'Invalid argument')

Can't open serial connection in Pyserial: "termios.error: (22, 'Invalid argument') "

6 Answers6

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