python serial write timeout

Question

I have used pyserial for a couple of days. However, a problem occurs today. I met serial write timeout. Several days before, when I used a switch, everything is OK. But today I changed for another switch. Then serial write timeout appears. I did not change any code, but the problem is actually quite severe. More seriously, the timeout not always occurs, which means that sometimes I can write in the serial successfully.

ser = serial.Serial( #Serial COM configuration
    port='COM5',
    baudrate=9600,
    parity=serial.PARITY_NONE,
    stopbits=serial.STOPBITS_ONE,
    bytesize=serial.EIGHTBITS,
    rtscts=True,
    timeout=2,
    writeTimeout=5
  )
strInput = "show ver"
ser.flushInput()
ser.flushOutput()
ser.write(strInput.encode('utf-8')+b'\n')

I have ensured that the port is COM5 and the baudrate of the switch is 9600. Thanks a lot for answering my question.

Thanks for answering. I have already tried those methods, but the problem still exists. — foreverXZC
– foreverXZC, Commented Aug 19, 2016 at 7:29

Community · Accepted Answer · 2017-05-23 12:26:17Z

1

I ran into this problem recently. I found that setting write_timeout=0 solved the issue (also, not really sure why a write timeout even exists...)

Another answer here suggests the same thing :)

edited May 23, 2017 at 12:26

CommunityBot

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answered May 9, 2017 at 10:47

linzwatt

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JardaG · Accepted Answer · 2020-10-31 15:51:58Z

1

The problem may be that the interface tries to comply with RTS, CTS, DSR, or DTS signals. It is possible that if they are not properly connected, they can mysteriously affect communication through a timeout.

One solution may be to ignore their influence using rtscts=False and/or dsrdtr=False when opening the serial port in Python.

answered Oct 31, 2020 at 15:51

JardaG

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Comments

user14220582 · Accepted Answer · 2020-09-04 10:59:21Z

0

If you have flow control with request to send / clear to send structure and the device you are writing to isn't responding you need the timeout for the write in order to not hang

answered Sep 4, 2020 at 10:59

user14220582

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