drivers/mq3: added driver for alcohol sensor

drivers/Makefile

@@ -46,5 +46,8 @@ endif
 ifneq (,$(filter isl29020,$(USEMODULE)))
     DIRS += isl29020
 endif
+ifneq (,$(filter mq3,$(USEMODULE)))
+    DIRS += mq3
+endif
 
 include $(RIOTBASE)/Makefile.base

drivers/include/mq3.h

@@ -0,0 +1,72 @@
+/*
+ * 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.
+ */
+
+/**
+ * @defgroup    driver_mq3 MQ-3 Alcohol Tester
+ * @ingroup     drivers
+ * @brief       Device driver for the MQ-3 alcohol sensor
+ * @{
+ *
+ * @file
+ * @brief       Device driver interface for the MQ-3 alcohol sensor
+ *
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ */
+
+#ifndef __MQ3_H
+#define __MQ3_H
+
+#include "periph/adc.h"
+
+#define MQ3_MAX_RAW_VALUE           (1023U)
+
+/**
+ * @brief device descriptor for a MQ-3 sensor
+ */
+typedef struct {
+    adc_t adc_dev;          /**< the used ADC device */
+    int adc_chan;           /**< used channel of the ADC */
+} mq3_t;
+
+/**
+ * @brief Initialize a MQ-3 alcohol sensor
+ *
+ * The MQ-3 sensor is interfaced by a single ADC pin, specified by `adc` and `channel`.
+ *
+ * @note The sensor needs about a minute to heat up before meaningful measurements
+ *       can be made.
+ *
+ * @param[out] dev      device descriptor of an MQ-3 sensor
+ * @param[in] adc       the ADC device the sensor is connected to
+ * @param[in] channel   the channel of the ADC device used
+ *
+ * @return              0 on success
+ * @return              -1 on error
+ */
+int mq3_init(mq3_t *dev, adc_t adc, int channel);
+
+/**
+ * @brief Read the RAW sensor value, can be between 0 and MQ3_MAX_RAW_VALUE
+ *
+ * @param[in] dev       device descriptor of the MQ-3 sensor to read from
+ *
+ * @return              the raw sensor value, between 0 and MQ3_MAX_RAW_VALUE
+ */
+int mq3_read_raw(mq3_t *dev);
+
+/**
+ * @brief Read the scaled sensor value of PPM of alcohol
+ *
+ * @param[in] dev       device descriptor of the MQ-3 sensor to read from
+ *
+ * @return              the scaled sensor value in PPM of alcohol
+ */
+int mq3_read(mq3_t *dev);
+
+#endif /* __MQ3_H */
+/** @} */

drivers/mq3/Makefile

@@ -0,0 +1,3 @@
+MODULE = mq3
+
+include $(RIOTBASE)/Makefile.base

drivers/mq3/mq3.c

@@ -0,0 +1,44 @@
+/*
+ * 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     driver_mq3
+ * @{
+ *
+ * @file
+ * @brief       Device driver implementation for the MQ-3 alcohol sensor
+ *
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ *
+ * @}
+ */
+
+#include "mq3.h"
+
+#define PRECISION           ADC_RES_10BIT
+#define MIN                 (100U)              /* TODO: calibrate to useful value */
+#define FACTOR              (2.33f)             /* TODO: calibrate to useful value */
+
+int mq3_init(mq3_t *dev, adc_t adc, int channel)
+{
+    dev->adc_dev = adc;
+    dev->adc_chan = channel;
+    return adc_init(dev->adc_dev, PRECISION);
+}
+
+int mq3_read_raw(mq3_t *dev)
+{
+    return adc_sample(dev->adc_dev, dev->adc_chan);
+}
+
+int mq3_read(mq3_t *dev)
+{
+    float res = mq3_read_raw(dev);
+    res = (res > MIN) ? res - MIN : 0;
+    return (int)(res * FACTOR);
+}