scanner.py

#!/usr/bin/env python3

import serial
import RPi.GPIO as GPIO


class BarcodeScanner:
    def __init__(self, trigger_pin=-1, port="/dev/ttyAMA0", baudrate=9600, timeout=1):
        self.trigger_pin = trigger_pin
        if trigger_pin != -1:
            # Setup GPIO for scan trigger if configured
            GPIO.setmode(GPIO.BCM)
            GPIO.setup(self.trigger_pin, GPIO.OUT)
            GPIO.output(self.trigger_pin, 1)
        self.__buffer = b""
        self.conn = serial.Serial(port, baudrate, timeout=timeout)

    """Try to scan barcode, return None if none is found
	"""

    def scan(self, repeated_scan):
        if self.trigger_pin != -1:
            # Enable trigger pin
            GPIO.output(self.trigger_pin, 0)
        elif not repeated_scan:
            # Scan will be active for set time, no need to resend on every interval
            # Enable serial control
            self.conn.write(b"\x7e\x00\x08\x01\x00\x00\xd5\xab\xcd")
            # Extend time to 20s zone 0x0006 = C8h / 200d
            self.conn.write(b"\x7e\x00\x08\x01\x00\x06\xc8\xab\xcd")
            # Trigger scanning
            self.conn.write(b"\x7e\x00\x08\x01\x00\x02\x01\xab\xcd")
        while self.conn.in_waiting:
            c = self.conn.read()
            if c == b"\r" or c == b"\n":
                if len(self.__buffer):
                    tmp = self.__buffer
                    self.__buffer = b""
                    return tmp.decode("utf-8")
            else:
                self.__buffer += c
                if self.__buffer == b"\x02\x00\x00\x01\x00\x33\x31":
                    self.__buffer = b""  # remove handshake notice
        return None

    """Release trigger
	"""

    def endScan(self):
        if self.trigger_pin != -1:
            # Disable trigger pin
            GPIO.output(self.trigger_pin, 1)
        else:
            # Switch to manual trigger
            self.conn.write(b"\x7e\x00\x08\x01\x00\x00\xd4\xab\xcd")
        self.__buffer = b""


if __name__ == "__main__":
    scanner = BarcodeScanner(18, "/dev/ttyS0")
    import time

    timeout = time.time() + 5
    res = None
    while res is None and timeout > time.time():
        res = scanner.scan()
    scanner.endScan()
    print(res)