import minimalmodbus
import serial
import time

class Sensor():
    holding_register_start = 40001
    holding_register_end = 49999
    input_register_start = 30001
    input_register_end = 39999
    baudrates = [ 4800,9600,14400,19200,28800,38400,57600,76800,115200 ]
    input_register_offset = { \
            'CO2': 9, \
            'T_SHT4x': 10, \
            'RH_SHT4x': 11, \
            'T_SCD4x': 12, \
            'RH_SCD4x': 13, \
            'T_SHT4x_signed': 14, \
            'T_SCD4x_signed': 15 }
    holding_register_offset = { \
            'LED_on_register': 0, \
            'LED_brightness_register': 1, \
            'LED_smooth_register': 2, \
            'CO2_alert_limit_1_register': 3, \
            'CO2_alert_limit_2_register': 4, \
            'SCD4x_temperature_offset_register': 5, \
            'MODBUS_address_register': 6, \
            'baudrate_register': 7 }
    def __init__(self, dev_file='/dev/rs485', address=247, baudrate=19200):
        self.dev_file = dev_file
        self.address = address
        self.baudrate = baudrate
        self.open()
    def open(self):
        self.serial = minimalmodbus.Instrument(self.dev_file, self.address, close_port_after_each_call=True)
        self.serial.serial.baudrate = self.baudrate
        self.serial.serial.bytesize = 8
        self.serial.serial.parity   = serial.PARITY_EVEN
        self.serial.serial.stopbits = 1
        self.serial.serial.timeout  = 0.05          # seconds
        self.serial.mode = minimalmodbus.MODE_RTU   # rtu or ascii mode
        self.serial.clear_buffers_before_each_transaction = True
    def close(self):
        self.serial.serial.close()
        self.serial = None
    # High level read functions
    @property
    def CO2(self):
        return self.read_input_register(self.input_register_offset['CO2'])*10
    @property
    def T(self):
        # TODO maybe use rather signed version?
        return self.T_SHT4x
    @property
    def RH(self):
        return self.RH_SHT4x
    @property
    def T_SHT4x(self):
        return self.read_input_register(self.input_register_offset['T_SHT4x'])
    @property
    def T_SHT4x_signed(self):
        return self.read_input_register(self.input_register_offset['T_SHT4x_signed'], signed=True)
    @property
    def RH_SHT4x(self):
        return self.read_input_register(self.input_register_offset['RH_SHT4x'])*10
    @property
    def T_SCD4x(self):
        return self.read_input_register(self.input_register_offset['T_SCD4x'])
    @property
    def T_SCD4x_signed(self):
        return self.read_input_register(self.input_register_offset['T_SCD4x_signed'], signed=True)
    @property
    def RH_SCD4x(self):
        return self.read_input_register(self.input_register_offset['RH_SCD4x'])*10
    def read_input_register(self, register_offset):
        retries = 10
        while retries:
            try:
                return self.serial.read_register(register_offset, 1, functioncode=4)
            except (minimalmodbus.NoResponseError, minimalmodbus.InvalidResponseError) as e:
                retries -= 1
                continue
        raise e
    # generic read register function
    def read_register(self, register_number):
        if self.input_register_start <= register_number <= self.input_register_end:
            function_code = 4
            register_offset = register_number - self.input_register_start
        elif self.holding_register_start <= register_number <= self.holding_register_end:
            function_code = 3
            register_offset = register_number - self.holding_register_start
        else:
            # wrong register number
            raise ValueError
        return self.serial.read_register(register_offset, 1, functioncode=function_code) * 10
    def write_register(self, register_number, register_value):
        if not self.holding_register_start <= register_number <= self.holding_register_end:
            raise ValueError
        register_offset = register_number - self.holding_register_start
        return self.serial.write_register(register_offset, register_value, functioncode=6)