/* * Copyright (C) 2014 Freie Universität Berlin * * This file is subject to the terms and conditions of the GNU Lesser General * Public License v2.1. See the file LICENSE in the top level directory for more * details. */ /** * @ingroup drivers_mq3 * @{ * * @file * @brief Device driver implementation for the MQ-3 alcohol sensor * * @author Hauke Petersen * * @} */ #include "mq3.h" #include "macros/math.h" #define PRECISION ADC_RES_10BIT /* TODO: calibrate to useful value */ #define MIN (100U) /* TODO: calibrate to useful value */ #define SHIFT (12U) #define FACTOR DIV_ROUND(233UL << SHIFT, 100) int mq3_init(mq3_t *dev, adc_t adc_line) { dev->adc_line = adc_line; return adc_init(dev->adc_line); } int16_t mq3_read_raw(const mq3_t *dev) { return adc_sample(dev->adc_line, PRECISION); } int16_t mq3_read(const mq3_t *dev) { uint32_t res = mq3_read_raw(dev); res = (res > MIN) ? res - MIN : 0; /* same as `(int16_t)(res * 2.33)` */ return (res * FACTOR) >> SHIFT; }