STM32F103C8T6 USBSerial Demo

File content as of revision 0:24604e97c40c:

#!/usr/bin/env python
from __future__ import print_function

import argparse
import sys
from time import sleep

import serial
from serial.tools.list_ports import comports
from six import binary_type

_DEFAULT_BAUD_RATE = 115200


def _reset_baud_drate(serial):
    original_baudrate = serial.baudrate
    i = serial.BAUDRATES.index(original_baudrate)
    if i == -1:
        raise ValueError("Unknown baudrate {}".format(original_baudrate))

    if i > 1:
        tmp_baud_rate = serial.BAUDRATES[i - 1]
    elif len(serial.BAUDRATES) > 1:
        tmp_baud_rate = serial.BAUDRATES[i + 1]
    else:
        raise ValueError("Only one baudreate is available")

    serial.baudrate = tmp_baud_rate
    serial.baudrate = original_baudrate


def _read_from_serial_device(port, out=sys.stdout, reconnect_on_error=True, repeat_delay=2, **port_params):
    print('Read from the serial port "{}" (use Ctrl+C to exit)'.format(port))
    while True:
        try:
            with serial.Serial(port=port, **port_params) as com_port:
                # hack:
                # when you connect usb-com port of the stm32f1 first time, it will work
                # but if you reconnect it, then it stop working, although com port readers doesn't show
                # any error.
                # However I found that it can be solved by 2 ways:
                # - host rebooting (but it's very inconvenient)
                # - changing baudrate. The new value doesn't matter, it should only be different than previous.
                #   Moreover the old values without any problems can be reverted without any problems.
                # TODO: find reason of such strange behavior
                _reset_baud_drate(com_port)
                for line in com_port:
                    if isinstance(line, binary_type):
                        line = line.decode('utf-8')
                    out.write(line)
                    out.flush()

        except serial.SerialException as e:
            print("Error: {}".format(e))
            if not reconnect_on_error:
                break
            sleep(repeat_delay)


def _guess_serial_device_name():
    ports = list(comports())
    if len(ports) == 1:
        port = ports[0].device
    elif len(ports) == 0:
        raise ValueError("No serial devices found")
    else:
        print("Several serial devices are found. Please specify one of them explicitly:")
        for port_info in ports:
            print("- {}".format(port_info.device))
        raise ValueError("Multiple serial devices are found.")

    return port


def main(args=None):
    parser = argparse.ArgumentParser(prog='serial_reader',
                                     description='Helper program that read text from a serial port. '
                                                 'Unlike other com programs it automatically reconnect '
                                                 'to serial port if any error occurs. It is useful for '
                                                 'microcntrollers debugging when you want to reboot it and'
                                                 'the connection will be lost for some time.')
    parser.add_argument('port', nargs='?', help='Serial port device name. It it is not specifies, then'
                                                'it will be found automatically if it is possible')
    parser.add_argument('--baudrate', default=_DEFAULT_BAUD_RATE,
                        help="baud rate. Default: {}".format(_DEFAULT_BAUD_RATE))
    parsed_args = parser.parse_args(args)

    if parsed_args.port is None:
        try:
            port = _guess_serial_device_name()
        except Exception as e:
            print(e)
            sys.exit(1)
    else:
        port = parsed_args.port

    try:
        _read_from_serial_device(
            port,
            baudrate=parsed_args.baudrate
        )
    except KeyboardInterrupt:
        print("Exit ...")


if __name__ == '__main__':
    main()