raspberry pi, python, linux shell commands, output and input control

Job Description:

my raspberry pi is connected to a "controller board" with an USB cable. This controller board is then connected to one "dual motor controller card" and one "dual quadrature encorder card" with ribbon cables.

On the raspberry pi, i will install a host program. With the host program, i can open a terminal, and send the commands to controller board to move the two motors and to read the encorder data of two motors on a robot. Everything is working perfectly when i do thing on a terminal (linux shell). However, I like to control the robot with python. Therefore I place all shell commands into a python code as attached file. The code is still working except that one line is bothering me, and the line is

[login to view URL] ("dpcat quad2 counts")

when this python line is executed, it will keep outputing 4 data on screen (1st problem) and it will not stop (2nd problem). I like your help to solve these two problems. Basically I like to output the data into variables in python so i can process them. For example, if python can read n1 each time, then we can set for example when the sum of all previous n1 is larger than a certain value, the program shall stop.

based on my reading, i may need to use python's "subprocess". please feel free to advise me the best approaches. Please note that my encorder may keep output the data every 10ms or 50ms, thus somehow, i do not want to output the data to a file and read back the data from the file, because i believe it is going to slow down the program. And i assume python can open a "pipe" to do this kind of work?

happy bidding

Навыки: Python, Linux, Архитектура ПО, Raspberry Pi

ID проекта: #27332582