SerialTimeoutException in Python not working as expected

Question

Sometimes I do not get any data in via the serial interface and I want to catch this case with an exception in the following way:

ser          = serial.Serial(3)
ser.baudrate = 115200
timeout      = 1

while (some condidion)
  try:
    dump = ser.read(40)
  except ser1.SerialTimeoutException:
    print('Data could not be read')

ser.close()

However, when I run this program, the exception is never caught when no data is in the buffer and I am stuck in an endless loop. Anyone an idea what I am doing wrong here?

Two things that may be typos / omissions in question code: 1. exception should probably be serial.SerialTimeoutException 2. you do not set the condition to False after catching the exception. — jhonkola
– jhonkola, Commented Jun 11, 2012 at 10:23
Nope, never saw it because the exception got never caught as glglgl explains below! — Patrick
– Patrick, Commented Jun 11, 2012 at 12:47

glglgl · Accepted Answer · 2016-01-21 08:33:07Z

7

I didn't even know about that exception. After having a look at the API documentation, you'll see that this exception only applies to write().

If you read(), you'll just have a shortened or even empty output.

And this applies only if you have opened the connection with a timeout. Something like serial.Serial(3, timeout=.1).

edited Jan 21, 2016 at 8:33

answered Jun 11, 2012 at 10:22

glglgl

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1 Comment

Patrick Over a year ago

brilliant, exactly what I was looking for. Works now ;)

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