roberto/raspberry/roberto/Serial.py

import time
import threading

import serial

class Serial(object):
    _callbacks = dict()

    def __init__(self, devicename='/dev/ttyUSB0', baudrate=115200):
        self.devicename = devicename
        self.alive = None
        try:
            self.serialport = serial.Serial(devicename, baudrate, timeout=3.0)
            self.serialport.flushInput()
            self.serialport.write(b'\n')
            self.alive = True
            print("Arduino connection established..")
        except serial.SerialException as e:
            print('could not open port {!r}: {}\n'.format(devicename, e))
#        except:
#            print("Failed to open serial device: " + self.serialport.name)

        self.receiver_thread = threading.Thread(target=self.reader, name='rx')
        self.receiver_thread.daemon = True
        self.receiver_thread.start()

    def __del__(self):
        self.alive = False
        self.serialport.close()

    def write(self, buf):
        if not self.alive:
            print("Serial port not connected")
            return
        try:
            if isinstance(buf, str):
                buf = bytes(buf, "utf8")
            self.serialport.flushInput()
            self.serialport.write(buf)
            #self.serialport.write(b'\n')  # or "\r\n" ?
            print("sent " + str(buf))
        except:
            print("Error writing to: " + self.serialport.name + " Data: " + str(buf))

    def reader(self):
        try:
            while self.alive and self.serialport:
                #data = self.serialport.read(self.serialport.in_waiting or 1)
                data = self.serialport.readline()
                if data:
                    print(data)
                    if isinstance(data, bytes):
                        data = data.decode(encoding='utf8')
                    command = data[0]
                    argument = data[2:].strip()
                    if command and command in self._callbacks:
                        callbacks = self._callbacks[command]
                        for cb, cb_arg in callbacks:
                            cb(argument, cb_arg)
                    else:
                        print("no callback found for command '%s'" % command)

        except serial.SerialException:
            pass
            #self.alive = False
            #raise

    def add_callback(self, cmd, callback, arg):
        if not cmd in self._callbacks:
            self._callbacks[cmd] = []
        self._callbacks[cmd].append( (callback, arg) )

    def del_callback(self, cmd, callback, arg):
        if cmd in self._callbacks:
            self._callbacks[cmd].remove( (callback, arg) )