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/*
* Copyright 2020 Birte Kristina Friesel
*
* SPDX-License-Identifier: BSD-2-Clause
*
* Driver for MAX44009 Ambient Light Sensor.
* Does not support interrupts.
*/
#include "driver/max44009.h"
#if defined(CONFIG_meta_driver_hardware_i2c)
#include "driver/i2c.h"
#elif defined(CONFIG_driver_softi2c)
#include "driver/soft_i2c.h"
#endif
float MAX44009::getLux()
{
unsigned char luxHigh;
unsigned char luxLow;
unsigned int mantissa, exponent;
txbuf[0] = 0x03;
txbuf[1] = 0x04;
if (i2c.xmit(address, 2, txbuf, 2, rxbuf) != 0) {
return -1;
}
luxHigh = rxbuf[0];
luxLow = rxbuf[1];
/*
* The lowest 4 bit of luxLow are the lowest 4 bit of the mantissa.
* The lowest 4 bit of luxHigh are the highest 4 bit of the mantissa.
*/
mantissa = (luxLow & 0x0F) + ((luxHigh & 0x0F) << 4);
/*
* The highest 4 bit of luxHigh are the 4 bit exponent
*/
exponent = (luxHigh & 0xF0) >> 4;
if (exponent == 0x0f) {
// overrange condition
return -1;
}
/*
* Cast base and mantissa to float to avoid calculation errors
* because of 16bit integer overflows.
*/
return (float)(1 << exponent) * (float)mantissa * 0.045;
}
MAX44009 max44009(0x4a);
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