Raspberry Pi_SaberTooth 2X12 and simple serial

Question

I'm trying to control a SaberTooth 2x12 connected to my Pi3. Based my Google research it seemed the best method was Simple Serial. I configured the Pi for Serial in raspi-config. Set the dip switches on the SaberTooth for simple serial and 9600 baud. I added a Level Shifter between the Pi and SaberTooth.

According to the Sabertooth documentation, with simple serial 1-127 controls the speed and direction of M1 and 128-255 speed and direction of M2. "0" shuts the motors off. When I run the code motor1 moves in one direction and one speed and will continue until power is removed.

As long as I'm sending a "number" of any value the same results: Motor 1 one speed and one direction. One thing the original code I was basing this off of use "ser.writeString". When I ran the code with that format it said Serial Object does not have "String". Can you advise what I'm doing wrong?

#! /user/bin/env python
# _*_ coding : utf-8 _*_

import time
import serial

ser = serial.Serial('/dev/serial0', 9600)
def main():
   print("Program Start")
   time.sleep(5)
   x=0
     while x < 4:
       ser.write("M1: 1\r\n")
       ser.write("M2: 128\r\n")
       time.sleep(2)
       ser.write("M1: 64\r\n")
       ser.write("M2: 192\r\n")
       time.sleep(2)
       ser.write("M1: 127\r\n")
       ser.write("M2: 255\r\n")
       time.sleep(2)
       ser.write("M1: 0\r\n")
       ser.write("M2: 0\r\n")
       time.sleep(2)
       x = x + 1

if __name__ == '_main_':
   main()

Here's the traceback of the error I was getting:

Traceback (most recent call last): 

File "MotorTest.py", line 27, in <module> main() 
File "MotorTest.py" , line 16 in main 
ser.writeString("M1: 1\r\n") 
AttributeError: 'Serial' object has no attribute 'writeString' 
------------ 
Program exited with code: 1

Answer 1

Thanks to Aurora001 for pointing me to https://github.com/MomsFriendlyRobotCompany/pysabertooth. Using this library I'm able to get the motor control I wanted. A couple of side notes to add. As mentioned in the comments above, when I used the library as is I got an Attribute Error: Serial module does not include "is_open". I modified the installed PySabertooth.py code by commenting out the "if not self.saber.is_open:" line in the open(self) function. Un-indented the next line "self.saber.open() and my program worked. The second note is for a Pi3 instead of '/dev/tty.usbserial' I used '/dev/serial0' Thanks again for your help!!