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drivers/mq3: avoid use of floats

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This commit is contained in:
Marian Buschsieweke 2023-05-31 20:05:11 +02:00
parent d742513b62
commit e29499cf3a
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GPG Key ID: CB8E3238CE715A94
2 changed files with 15 additions and 10 deletions
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8
drivers/include/mq3.h
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@ -50,8 +50,8 @@ typedef struct {
* @param[out] dev device descriptor of an MQ-3 sensor
* @param[in] adc_line the ADC device the sensor is connected to
*
* @return 0 on success
* @return -1 on error
* @retval 0 success
* @retval -1 failure
*/
int mq3_init(mq3_t *dev, adc_t adc_line);
@ -62,7 +62,7 @@ int mq3_init(mq3_t *dev, adc_t adc_line);
*
* @return the raw sensor value, between 0 and MQ3_MAX_RAW_VALUE
*/
int mq3_read_raw(const mq3_t *dev);
int16_t mq3_read_raw(const mq3_t *dev);
/**
* @brief Read the scaled sensor value of PPM of alcohol
@ -71,7 +71,7 @@ int mq3_read_raw(const mq3_t *dev);
*
* @return the scaled sensor value in PPM of alcohol
*/
int mq3_read(const mq3_t *dev);
int16_t mq3_read(const mq3_t *dev);
#ifdef __cplusplus
}

17
drivers/mq3/mq3.c
View File

@ -19,10 +19,14 @@
*/
#include "mq3.h"
#include "macros/math.h"
#define PRECISION ADC_RES_10BIT
#define MIN (100U) /* TODO: calibrate to useful value */
#define FACTOR (2.33f) /* TODO: calibrate to useful value */
/* 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)
{
@ -30,14 +34,15 @@ int mq3_init(mq3_t *dev, adc_t adc_line)
return adc_init(dev->adc_line);
}
int mq3_read_raw(const mq3_t *dev)
int16_t mq3_read_raw(const mq3_t *dev)
{
return adc_sample(dev->adc_line, PRECISION);
}
int mq3_read(const mq3_t *dev)
int16_t mq3_read(const mq3_t *dev)
{
float res = mq3_read_raw(dev);
uint32_t res = mq3_read_raw(dev);
res = (res > MIN) ? res - MIN : 0;
return (int)(res * FACTOR);
/* same as `(int16_t)(res * 2.33)` */
return (res * FACTOR) >> SHIFT;
}