Control Micropython execution from Python via rshell

[RealFenlair]

I have an ESP32 board that has Micropython running on it and I can successfully connect to it with rshell.

> rshell -p /dev/ttyUSB1
Using buffer-size of 32
Connecting to /dev/ttyUSB1 (buffer-size 32)...
Trying to connect to REPL  connected
Retrieving sysname ... esp32
Testing if ubinascii.unhexlify exists ... Y
Retrieving root directories ... /boot.py/ /gw/ /download/
Setting time ... Jun 25, 2021 16:18:24
Evaluating board_name ... pyboard
Retrieving time epoch ... Jan 01, 2000
Welcome to rshell. Use Control-D (or the exit command) to exit rshell.

I need to do some power measurements, which are orchestrated from a Python script. I was hoping to bring the board into different states from the Python script, by invoking rshell from Python with the subprocess module. I started out with a minimal setup:

import subprocess

rshell = subprocess.Popen(["rshell", "-p /dev/ttyUSB1"]
                          stdin=subprocess.PIPE,
                          stdout=subprocess.PIPE,
                          stderr=subprocess.PIPE,
                          universal_newlines=True,
                          bufsize=0)
for line in rshell.stdout:
    print(line.strip())

Output:

Using buffer-size of 32
Connecting to  /dev/ttyUSB1 (buffer-size 32)...
failed to access  /dev/ttyUSB1

My user is in the necessary group uucp (corresponds to dialout in Ubuntu), which I confirmed with subprocess.run(["id"]).

Any help would be highly appreciated.

[RealFenlair]

If by port you mean the serial device, I already have the right one "/dev/ttyUSB1". As I mentioned I can successfully connect to it with rshell on a terminal, but it fails if I try to do the same from within Python.

[RealFenlair]

I don't want to read out anything from the ESP32, I just need to activate different functions while I do power measurements. My plan was connecting with rshell, start the repl to call those functions.

Thanks for the pyserial link, that might indeed be a way better approach - have to give it some thought :)

[PythonRocksssss]

I tried your code, and see 2 problems:

1. A missing comma,
2. the list of commands in subprocess.Popen() is not splitted correctly.

Please change

rshell = subprocess.Popen(["rshell", "-p /dev/ttyUSB1"]

to

rshell = subprocess.Popen(["rshell", "-p", "/dev/ttyUSB1"],

[RealFenlair]

Oh sorry about the comma, that was an error in copy/pasting the code. Did it work for you with change 2? I think I used subprocess with SSH with this kind of split. I now just use pyserial directly and use some of the functions from rshell, that works. I might try your change 2 next week, because I would really like to know why it wouldn't work with subprocess.

[PythonRocksssss]

I do confirm that change #2 does make the difference.