Frustration debugging serial code

[MRAB]

William R. Wing (Bill Wing) wrote:
> Hello World -
> I'm new to both Python and this list, but here's hoping someone can spot 
> my problem.
> 
> System:  Mac OS-X, 10.6.3 (Intel dual quad processor)
> Using Python 2.6.1, and pyserial-2.5_rc2-py2.6
> 
> The following snippet of code is designed to open a port via a KeySpan 
> USB-to-serial converter and communicate with an X10 power line signaling 
> system.  Before you look at the code, let me mention that my frustration 
> is the it executes perfectly if i enter it line by line at the Python 
> prompt, and executes perfectly if I run it under the Wing IDE.  It fails 
> silently (no errors) if I run it as a standalone script.  Clearly, I'm 
> missing something.
> 
What do you mean "It fails silently"? It might be unable to find the
modules if you double-click on the script. You could check for that by
printing a message if the import statement raises an ImportError.

> TIA,
> Bill Wing
> 
> import serial, string
> 
> port = '/dev/tty.KeySerial1'
> 
> ser = serial.Serial(port, 9600, timeout=1)   # Set up handle to serial port
> stat1 = ser.write('\x02')                    # Write "Attention" to 
> PowerLink
> print(' Stat1 is:', stat1)                   
> ack = ser.read(2)                            # Check to see if PowerLink 
> is ready
> if ack == '\x06\r':                          # It returns ACK (\x06) \r 
> if it is
>     stat2 = ser.write('\x63\x4E\x5C\x45\x41')# send "On" to module at 
> House Code B, device code 2
>     print(' Stat2 is:', stat2)
>     stat3 = ser.close()                      # Close serial port
>     print(' Stat3 is:', stat3)
> elif ack =='\x15':                           # PowerLink sends NAC (hex 
> 15) if it isn't.
>     print('Received NAK after first open')
> else:   print("Something's wrong at 1.\n")
> 
> dummy = raw_input(' Hit any key to continue: ')
>