SerialHandler.py

from PyQt5.Qt import *
import threading
import serial
import time

from collections import namedtuple
from MotorCommand import MotorCommand

from array import array

from io import BytesIO

from struct import *

"""
Class Serial handler

This class opens a serial device with the defined port and baudrate
and keeps emiting messages using pyqt signals

"""
class SerialHandler(QObject):

    bufferUpdated = pyqtSignal(tuple)
    startThread = pyqtSignal()
    stopThread  = pyqtSignal()
    pauseThread = pyqtSignal()
    resumeThread  = pyqtSignal()
    flushSerial = pyqtSignal()

    def __init__(self, parent):
        super(SerialHandler, self).__init__()
        self.running = False
        self.pause = False
        self.thread = threading.Thread(target=self.serialHandlerThread)
        self.device = 'COM4'
        self.baudrate = 115200
        self.rate = 1000000

        # prepare connections with parent window
        self.startThread.connect(self.startProcess)
        self.stopThread.connect(self.stopProcess)
        self.pauseThread.connect(self.pauseProcess)
        self.resumeThread.connect(self.resumeProcess)
        self.flushSerial.connect(self.flush)

        self.alone = None
        self.compound = None
        self.refMsg = None

        self.cmd = MotorCommand()
        self.serial_mutex = threading.Lock()

        self.ser = serial.Serial()

        # estructura del mensaje
        self.struct_fmt = '<BBhhh'
        self.struct_len = calcsize(self.struct_fmt)

    def set_COM_port_settings(self, com_port):
    	self.ser.port = self.device
    	self.ser.baudrate = self.baudrate
    	self.ser.bytesize = serial.EIGHTBITS 	#number of bits per bytes
    	self.ser.parity = serial.PARITY_NONE 	#set parity check: no parity
    	self.ser.stopbits = serial.STOPBITS_ONE #number of stop bits
    	self.ser.timeout = 3            		#non-block read
    	self.ser.xonxoff = False     			#disable software flow control
    	self.ser.rtscts = False     			#disable hardware (RTS/CTS) flow control
    	self.ser.dsrdtr = False      			#disable hardware (DSR/DTR) flow control
    	self.ser.writeTimeout = 3     			#timeout for write

    def __exit__(self, exc_type, exc_value, traceback):
        self.stopProcess()

    def setInterface(self, device, baudrate):
        self.ser.port = device
        self.ser.baudrate = baudrate
        self.device = device
        self.baudrate = baudrate


    def isRunning(self):
        return (self.running or not self.pause)

    def to_hex(self,data):
        return ":".join("{:02x}".format(c) for c in data)

    def send_command(self,command):

        self.set_command(command)

        buff = BytesIO()
        self.cmd.serialize(buff)

        #print(self.to_hex(buff.getvalue()))
        #print(buff.getvalue())

        base_cmd_int = bytearray(buff.getvalue())
        #checksum = 255 - ( sum(base_cmd_int) % 256 )
        # Packet: FF  FF  BASE_CMD  CHECKSUM
        #packet = bytearray([0xFF, 0xFF]) + base_cmd_int + bytearray([checksum]) + bytearray([0x0D])

        packet = bytearray([0xFF,0xFF]) + base_cmd_int + bytearray([0x0D])
        packet_str = array('B', packet).tostring()
        with self.serial_mutex:
            self.write_serial(packet_str)

    def write_serial(self, data):
        """
        Write in the serial port.
        """
        #print(self.cmd)
        #print("Hex: {}".format(to_hex(data)))
        self.ser.flushInput()
        self.ser.flushOutput()
        self.ser.write(data)

    def set_command(self,command):

        self.cmd.id = command.id
        self.cmd.cmd = command.cmd
        self.cmd.pref = command.pref
        self.cmd.P = command.P
        self.cmd.I = command.I
        self.cmd.D = command.D

    # pyqt signals definition

    @pyqtSlot()
    def startProcess(self):
        self.running = True
        self.thread.start()

    @pyqtSlot()
    def stopProcess(self):
        self.running = False

    @pyqtSlot()
    def pauseProcess(self):
        self.pause = True

    @pyqtSlot()
    def resumeProcess(self):
        self.pause = False

    @pyqtSlot()
    def flush(self):
        #self.ser.reset_input_buffer()
        print(self.ser.readline())

    @pyqtSlot(int)
    def setRate(self, rate):
        self.rate = rate

    # main thread
    def serialHandlerThread(self):

        while self.running is True:
            # read messages
            try:
                if self.ser.inWaiting():
                    msg = self.ser.read(self.struct_len)
                    #print(msg.decode())
                    if len(msg) != 0:
                        rxCom = unpack(self.struct_fmt, msg)
                        self.bufferUpdated.emit(rxCom)
                        #print(type(rxCom))

            except Exception as e:
                print(e)

            #else:
            #    pass

            # handle sampling rate
            #time.sleep(1/self.rate)

        self.ser.write(bytes('q\n','UTF-8'))
        self.ser.close()
        return 0