Source code for PyExpLabSys.drivers.inficon_sqm160

""" Driver for Inficon SQM160 QCM controller """
import serial
import time


class InficonSQM160(object):
    """ Driver for Inficon SQM160 QCM controller """

    def __init__(self, port='/dev/ttyUSB0', baudrate=9600):
        self.serial = serial.Serial(
            port=port,
            baudrate=baudrate,
            timeout=2,
            bytesize=serial.EIGHTBITS,
            xonxoff=True,
        )

    def comm(self, command):
        """ Implements actual communication with device """
        length = chr(len(command) + 34)
        crc = self.crc_calc((length + command).encode())
        command = '!' + length + command + chr(crc[0]) + chr(crc[1])
        command_bytes = bytearray()
        for i in range(0, len(command)):
            command_bytes.append(ord(command[i]))
        error = 0
        while (error > -1) and (error < 20):
            self.serial.write(command_bytes)
            time.sleep(0.1)
            reply = self.serial.read(self.serial.inWaiting())
            crc = self.crc_calc(reply[1:-2])
            try:
                crc_ok = reply[-2] == crc[0] and reply[-1] == crc[1]
            except IndexError:
                crc_ok = False
            if crc_ok:
                error = -1
                return_val = reply[3:-2]
            else:
                error = error + 1
        return return_val

    @staticmethod
    def crc_calc(input_string):
        """ Calculate crc value of command """
        command_string = []
        for i in range(0, len(input_string)):
            command_string.append(input_string[i])
        crc = int('3fff', 16)
        mask = int('2001', 16)
        for command in command_string:
            crc = command ^ crc
            for i in range(0, 8):
                old_crc = crc
                crc = crc >> 1
                if old_crc % 2 == 1:
                    crc = crc ^ mask
        crc1_mask = int('1111111', 2)
        crc1 = (crc & crc1_mask) + 34
        crc2 = (crc >> 7) + 34
        return (crc1, crc2)

    def show_version(self):
        """ Read the firmware version """
        command = '@'
        return self.comm(command)

    def show_film_parameters(self):
        """ Read the film paramters """
        command = 'A1?'
        print(self.comm(command))

    def rate(self, channel=1):
        """ Return the deposition rate """
        command = 'L' + str(channel)
        value_string = self.comm(command)
        rate = float(value_string)
        return rate

    def thickness(self, channel=1):
        """ Return the film thickness """
        command = 'N' + str(channel)
        value_string = self.comm(command)
        thickness = float(value_string)
        return thickness

    def frequency(self, channel=1):
        """ Return the frequency of the crystal """
        command = 'P' + str(channel)
        value_string = self.comm(command)
        frequency = float(value_string)
        return frequency

    def crystal_life(self, channel=1):
        """ Read crystal life """
        command = 'R' + str(channel)
        value_string = self.comm(command)
        life = float(value_string)
        return life


if __name__ == "__main__":
    INFICON = InficonSQM160(baudrate=19200)
    print('Controler version: ', INFICON.show_version())

    print('Rate channel 1: ', INFICON.rate(1))
    print('Thinkness channel 1: ', INFICON.thickness(1))
    print('Frequency channel 1: ', INFICON.frequency(1))
    print('Crystal life channel 1: ', INFICON.crystal_life(1))