tsl2591.py

# tsl2591 lux sensor interface
import time

VISIBLE = 2
INFRARED = 1
FULLSPECTRUM = 0

ADDR = 0x29
READBIT = 0x01
COMMAND_BIT = 0xA0
CLEAR_BIT = 0x40
WORD_BIT = 0x20
BLOCK_BIT = 0x10
ENABLE_POWERON = 0x01
ENABLE_POWEROFF = 0x00
ENABLE_AEN = 0x02
ENABLE_AIEN = 0x10
CONTROL_RESET = 0x80
LUX_DF = 408.0
LUX_COEFB = 1.64
LUX_COEFC = 0.59
LUX_COEFD = 0.86

REGISTER_ENABLE = 0x00
REGISTER_CONTROL = 0x01
REGISTER_THRESHHOLDL_LOW = 0x02
REGISTER_THRESHHOLDL_HIGH = 0x03
REGISTER_THRESHHOLDH_LOW = 0x04
REGISTER_THRESHHOLDH_HIGH = 0x05
REGISTER_INTERRUPT = 0x06
REGISTER_CRC = 0x08
REGISTER_ID = 0x0A
REGISTER_CHAN0_LOW = 0x14
REGISTER_CHAN0_HIGH = 0x15
REGISTER_CHAN1_LOW = 0x16
REGISTER_CHAN1_HIGH = 0x17
INTEGRATIONTIME_100MS = 0x00
INTEGRATIONTIME_200MS = 0x01
INTEGRATIONTIME_300MS = 0x02
INTEGRATIONTIME_400MS = 0x03
INTEGRATIONTIME_500MS = 0x04
INTEGRATIONTIME_600MS = 0x05

GAIN_LOW = 0x00
GAIN_MED = 0x10
GAIN_HIGH = 0x20
GAIN_MAX = 0x30

def _bytes_to_int(data):
    return data[0] + (data[1]<<8)

from machine import I2C, Pin
class SMBusEmulator:
    __slots__ = ('i2c',)
    def __init__(self, scl_pinno=5, sda_pinno=4):
        self.i2c = I2C(scl=Pin(scl_pinno, Pin.IN),
                       sda=Pin(sda_pinno, Pin.IN))

    def write_byte_data(self, addr, cmd, val):
        buf = bytes([cmd, val])
        self.i2c.writeto(addr, buf)

    def read_word_data(self, addr, cmd):
        assert cmd < 256
        buf = bytes([cmd])
        self.i2c.writeto(addr, buf)
        data = self.i2c.readfrom(addr, 4)
        return _bytes_to_int(data)

SENSOR_ADDRESS=0x29

class Tsl2591:
    def __init__(
                 self,
                 sensor_id,
                 integration=INTEGRATIONTIME_100MS,
                 gain=GAIN_LOW
                 ):
        self.sensor_id = sensor_id
        self.bus = SMBusEmulator()
        self.integration_time = integration
        self.gain = gain
        self.set_timing(self.integration_time)
        self.set_gain(self.gain)
        self.disable()

    def set_timing(self, integration):
        self.enable()
        self.integration_time = integration
        self.bus.write_byte_data(
                    SENSOR_ADDRESS,
                    COMMAND_BIT | REGISTER_CONTROL,
                    self.integration_time | self.gain
                    )
        self.disable()

    def set_gain(self, gain):
        self.enable()
        self.gain = gain
        self.bus.write_byte_data(
                    SENSOR_ADDRESS,
                    COMMAND_BIT | REGISTER_CONTROL,
                    self.integration_time | self.gain
                    )
        self.disable()

    def calculate_lux(self, full, ir):
        if (full == 0xFFFF) | (ir == 0xFFFF):
            return 0
            
        case_integ = {
            INTEGRATIONTIME_100MS: 100.,
            INTEGRATIONTIME_200MS: 200.,
            INTEGRATIONTIME_300MS: 300.,
            INTEGRATIONTIME_400MS: 400.,
            INTEGRATIONTIME_500MS: 500.,
            INTEGRATIONTIME_600MS: 600.,
            }
        if self.integration_time in case_integ.keys():
            atime = case_integ[self.integration_time]
        else:
            atime = 100.

        case_gain = {
            GAIN_LOW: 1.,
            GAIN_MED: 25.,
            GAIN_HIGH: 428.,
            GAIN_MAX: 9876.,
            }

        if self.gain in case_gain.keys():
            again = case_gain[self.gain]
        else:
            again = 1.

        cpl = (atime * again) / LUX_DF
        lux1 = (full - (LUX_COEFB * ir)) / cpl

        lux2 = ((LUX_COEFC * full) - (LUX_COEFD * ir)) / cpl

        return max([lux1, lux2])

    def enable(self):
        self.bus.write_byte_data(
                    SENSOR_ADDRESS,
                    COMMAND_BIT | REGISTER_ENABLE,
                    ENABLE_POWERON | ENABLE_AEN | ENABLE_AIEN
                    )

    def disable(self):
        self.bus.write_byte_data(
                    SENSOR_ADDRESS,
                    COMMAND_BIT | REGISTER_ENABLE,
                    ENABLE_POWEROFF
                    )

    def get_full_luminosity(self):
        self.enable()
        time.sleep(0.120*self.integration_time+1)
        full = self.bus.read_word_data(
                    SENSOR_ADDRESS, COMMAND_BIT | REGISTER_CHAN0_LOW
                    )
        ir = self.bus.read_word_data(
                    SENSOR_ADDRESS, COMMAND_BIT | REGISTER_CHAN1_LOW
                    )                    
        self.disable()
        return full, ir

    def get_luminosity(self, channel):
        full, ir = self.get_full_luminosity()
        if channel == FULLSPECTRUM:
            return full
        elif channel == INFRARED:
            return ir
        elif channel == VISIBLE:
            return full - ir
        else:
            return 0

    def sample(self):
        full, ir = self.get_full_luminosity()
        return self.calculate_lux(full, ir)