Stefano Costa

The pySerial library is really good. Today I installed it and in half an hour I got acquainted with its class methods, even though I have little knowledge about serial ports and the like.

With some trial and error about the connection parameters, I was even able to solve the problem with non-printable characters, tweaking the bytesize of the connection.

Briefly, these are the steps I did in the interactive ipython console:

1. >>> import serial
   >>> ser = serial.Serial('/dev/ttyUSB0', \
   baudrate=9600, bytesize=serial.SEVENBITS, timeout=0, \
   parity=serial.PARITY_NONE, rtscts=1)
   >>> ser.open()

2. at this point, start the transfer from the device
3. check that you have received some data:

   >>> ser.inWaiting()
   648L
   

   A non-zero result means that you have received something.

4. I saved this value to use it with the read() method of the Serial class:

   >>> n = ser.inWaiting()
   >>> result = ser.read(n)
   

5. The result object is a string, seeing its contents is as simple as:

   >>> print(result)
   0001 OR.COOR
   0002                   0S        X        0.000 Y         0.000 Z     0.000
   0003                                            Om     397.0370
   0004 POLAR
   0005 INPUT                       th       1.500 ih        0.000
   0006 INPUT                       th       0.000 ih        0.000 Z     0.000
   0007                   1         X       -0.472 Y         1.576 Z     0.004
   END
   

   As you can see, there are no errors after the END sentence, because the serial connection is handled gracefully now. The previous attempt with cat /dev/ttyUSB0 was a bit brutal…

For now, that’s all. I go back studying and maybe also writing some Python code for this Total Station. If you have got a total station and want to contribute to this project, let me know by leaving a comment here.