Problems with serial port interface
MRAB
python at mrabarnett.plus.com
Fri Jun 7 10:18:17 EDT 2013
On 07/06/2013 11:17, lionelgreenstreet at gmail.com wrote:
> Sorry for my quote,
> but do you have any suggestion?
>
> Il giorno martedì 4 giugno 2013 23:25:21 UTC+2, lionelgr... at gmail.com ha scritto:
>> Hi,
>>
>> i'm programming in python for the first time: i want to create a serial port reader. I'm using python3.3 and pyQT4; i'm using also pyserial.
>>
>> Below a snippet of the code:
>>
>>
>> class CReader(QThread):
>> def start(self, ser, priority = QThread.InheritPriority):
>> self.ser = ser
>> QThread.start(self, priority)
>> self._isRunning = True
>> self.numData=0;
>>
>> def run(self):
>> print("Enter Creader")
>> while True:
>> if self._isRunning:
>> try:
>> data = self.ser.read(self.numData)
>> n = self.ser.inWaiting()
>> if n:
>> data = self.ser.read(n)
>> self.emit(SIGNAL("newData(QString)"), data.decode('cp1252', 'ignore'))
>> self.ser.flushInput()
>> except:
>> pass
>> else:
>> return
>>
>> def stop(self):
>> self._isRunning = False
>> self.wait()
>>
>> This code seems work well, but i have problems in this test case:
>>
>> +baud rate:19200
>> +8/n/1
>> +data transmitted: 1 byte every 5ms
>>
>> After 30seconds (more or less) the program crashes: seems a buffer problem, but i'm not really sure.
>>
>> What's wrong?
>>
Using a "bare except" like this:
try:
...
except:
...
is virtually always a bad idea. The only time I'd ever do that would
be, say, to catch something, print a message, and then re-raise it:
try:
...
except:
print("Something went wrong!")
raise
Even then, catching Exception would be better than a bare except. A
bare except will catch _every_ exception, including NameError (which
would mean that it can't find a name, possibly due to a spelling error).
A bare except with pass, like you have, is _never_ a good idea. Python
might be trying to complain about a problem, but you're preventing it
from doing so.
Try removing the try...except: pass and let Python tell you if it has a
problem.
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