Just for info: easily read/write from/to Smart Stepper by raspberry pi/bash about nano_stepper HOT 1 OPEN

import serial
import time
import termios # workaround for IOError on resetting input/output buffers
import re

# note that when defining serial.Serial will automatically open the port!
ser=None
def createSerial():
        global ser
        time.sleep(1) # always wait one second before re-opening. This prevents hiccups
        try:
                #print("trying to open serial connection")
                ser=serial.Serial(
                        port="/dev/ttyUSB-SMART-A-AXIS",
                        baudrate=115200,
                        bytesize=serial.EIGHTBITS,
                        parity=serial.PARITY_NONE,
                        stopbits=serial.STOPBITS_ONE,
                        timeout=1,
                        xonxoff=False,
                        rtscts=False,
                        write_timeout=1,
                        dsrdtr=False,
                        inter_byte_timeout=None,
                        exclusive=True) # force to get behaviour "Cannot open line '/dev/ttyUSB-SMART-A-AXIS' for R/W: open() blocked, aborted." or "Error: read failed: device reports readiness to read but returned no data (device disconnected or multiple access on port?)"

        except IOError as e: # the serial creation may fail if device not connected or not ready
                print("Error:", e)
                pass
while True:
        if ser == None:
                #print("serial is set to None. Creating new serial connection")
                createSerial()
        else:
                try:
                        ser.reset_input_buffer()
                        ser.reset_output_buffer()
                        ser.write("ctrlmode".encode() + b'\r')
                        #time.sleep(0.05)
                        while ser.inWaiting() > 0:
                                line=ser.readline().decode()
                                #print(line)
                                p=re.compile(r'^controller\s.*\(\d\)$', re.M)
                                m=p.search(line)
                                if m:
                                        print("ctrlmode =",m.group(0)[-2]) #extract the number from "controller <modeString> (<number>)"
                except (IOError, termios.error) as e: # in case the USB device was removed or buffer reset fails try to close and re-open serial port
                        print("Error:", e)
                        ser.close()
                        ser = None #unset
                        createSerial()
                        pass