Controlling MDrive 23 ( schneider elect ) with Python....

hi all...this forum looks like it has the group of people I need...the SE site is for the pros of interface design
and I'm trying to work with linux and python.

I've got the linux program screen to connect to the motor (Via USB /dev/ttyUSB0 ) and make the motor execute basic commands.
However my PySerial commands haven't worked yet...and I'm lost now.

I don't understand some communication details and what to configure them as, other than baud rate...
parity, stop bits, num of bit/byte...

Cheers,
wbg

import serial
ser = serial.Serial('/dev/ttyUSB0', 19200)
ser.isOpen() # returns True
ser.write('ma 100000\r\n') # does nothing...
ser.inWaiting() # returns 0
ser.close()