Handle encoding error in mks_g_series driver #19
Conversation
In PyExpLabSys/drivers/mks_g_series.py, MksGSeries.com() now handles the error rather than crashing when the flow controller sends it a response it can't decode to ascii. Also fixed the name of the MksGSeries class in macines/rasppi89/socket_server.py and made that script python3-compatible by converting a dict.keys() to list before indexing.
| @@ -35,7 +38,10 @@ def comm(self, command, addr): | |||
| self.ser.write(com_string) | |||
| time.sleep(0.1) | |||
| reply = self.ser.read(self.ser.inWaiting()) | |||
| reply = reply.decode() | |||
| try: #some MFC communication gives UnicodeDecodeError | |||
| reply = reply.decode() | |||
There was a problem hiding this comment.
Not related to this PR, but the default behavior of decode() without arguments has changed from 'ascii' to 'utf-8'. Most likely, the intention is that it should be ascii and getting bytes that cannot be decoded as ascii is a communications error. So trying to decode as utf-8 might in principle allow scrambled message to be decoded and the fault will appear somewhere else. I suggest to explicitely add the 'ascii' argument to decode.
There was a problem hiding this comment.
Changing from ascii to utf-8 was actually the first thing I tried. I changed, a few lines above in the same function,
com_string = com_string.encode('ascii')
to
com_string = com_string.encode('utf-8')
Gave the same error message. But of course in hindsight that makes sense, after I figured out it was the returning message that gave the error.
Strangely, though, this wasn't a problem before updating the rest of the drive to Robert's version. It's not a py2 vs py3 thing since I tried both...
I'll try your suggestion, and make a new pull request if it works, next time I have down time between experiments at my setup. It's a kind of tedious process to edit in on the rasppi (a requirement so that I can test it) and then copy it over to my fork to pull request it, but I think it's worth it for now so you can suggest changes just like this.
In PyExpLabSys/drivers/mks_g_series.py, MksGSeries.com() now handles the error rather than crashing when the flow controller sends it a response it can't decode to ascii.
Also fixed the name of the MksGSeries class in macines/rasppi89/socket_server.py and made that script python3-compatible by converting a dict.keys() to list before indexing.