[Pythonmac-SIG] Serial port IO on Python 2.7.3 on OS X

[Ronald Oussoren]

On 8 Jun, 2012, at 2:16, Mike Wirth wrote:

> Hi, folks,
> 
> Newbie (to Python) here.  I'm porting a Python app from Windows that talks to a Bluetooth 2.1 device using the serial profile (on WinXP it shows up as two numbered COM ports, one inbound and the other outbound)  On the Mac, the device shows up in /dev as:
> 
>     crw-rw-rw-  1 root  wheel   18,   7 May 30 23:12 cu.BlueRadios-COM0
> 
> On Windows, the app requires me to install pyserial (and pygame for the visual output).  
> 
> On the Mac, where I've installed and am using python 2.7.3 (rather than the pre-installed 2.6.7), my app starts up and acts like it doesn't need to have pyserial installed, but of course, it can't connect to the expected numbered COM port.
> 
> 1. Do I need the Mac equivalent of pyserial?

pyserial works fine on OSX. 

> 2. Or can I just stuff something like '/dev/cu.BlueRadios-COM0' in the app's source code where it expects to open the serial port.

Probably.  The last time I used pyserial on OSX I just used numeric indexes to probe for the device:

for pn in range(10):
    try:
        port = serial.Serial(pn, timeout=0.5)
        break
    except serial.SerialException:
        pass
else:
    raise RuntimeError("Cannot find port")

The main advantage for me was that the same code works on Windows as well.


> 3. Anything special about the Bluetooth serial profile (e.g., setting port properties)?

I haven't used Bluetooth, with some luck the exposed serial device can be configured just like any other serial device using pyserial.

There is a low-level Bluetooth framework as well, but I don't know if someone has writting python bindings for that.

Ronald

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