Controlling MDrive 23 with Python under Linux - arduino

Question

MDrive 23 motor takes commands from a terminal, and I got it to work with screen program:
screen /dev/ttyUSB0
Is this is called a serial terminal? I'm unfamiliar with the details of the connection, but feel like I should be able to use PySerial to send the commands.
I tried:
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()
I didn't know how to set the other init variables, like:
parity = serial.PARITY_ODD,
stopbits = serial.STOPBITS_TWO
bytesize = serial.SEVENBITS
I'm going to try guessing some values next... The documentation is lame, but it mentions MODBUS TCP and Mcode.
How do I set these and are there any syntax errors in my snippet?
I know how to send arguments to the Serial object, but I do not know what values are typical.

Answer 1

The other parameters to the Serial constructor are set in a similar way as port and baudrate:
ser = serial.Serial(port = '/dev/ttyUSB0', baudrate=19200, bytesize=serial.SEVENBITS, parity=serial.PARITY_ODD, stopbits=serial.STOPBITS_TWO)
ser.write('whatever')
ser.flush() # wait for data to be written
ser.close()
Edit: It seems the default settings are 9600 baud, 8 bits, no parity and 1 stop bit. In addition no flow-control is used. That would be equivalent to:
ser = serial.Serial(port = '/dev/ttyUSB0', baudrate=9600, bytesize=serial.EIGHTBITS, parity=serial.PARITY_NONE, stopbits=serial.STOPBITS_ONE, xonxoff=False, rtscts=False, dsrdtr=False)
As all values, except port, are set to their defaults, you may use:
ser = serial.Serial(port = '/dev/ttyUSB0')
The last thing to worry about is which (read) timeout to set. This is measured/set in seconds (float allowed) and sets how long a read() command will block before returning what has been read.