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Merge #19609

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19609: drivers/lpsxxx: avoid float arithmetics r=aabadie a=maribu

### Contribution description

Perform computation directly in centi-degree-celsius to avoid floating point arithmetics. In addition, use scientific rounding in the division.


Co-authored-by: Marian Buschsieweke <marian.buschsieweke@ovgu.de>
This commit is contained in:
bors[bot] 2023-05-19 07:49:57 +00:00 committed by GitHub
commit 2327d74d24
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1 changed files with 14 additions and 9 deletions
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23
drivers/lpsxxx/lpsxxx.c
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@ -30,6 +30,7 @@
#include "periph/i2c.h" #include "periph/i2c.h"
#include "lpsxxx.h" #include "lpsxxx.h"
#include "lpsxxx_internal.h" #include "lpsxxx_internal.h"
#include "macros/math.h"
#define ENABLE_DEBUG 0 #define ENABLE_DEBUG 0
#include "debug.h" #include "debug.h"
@ -41,12 +42,14 @@
/** /**
* @brief temperature base value and divider for norming temperature output * @brief temperature base value and divider for norming temperature output
*
* @details temperature base is given in centi-degree-celsius
*/ */
#if MODULE_LPS331AP || MODULE_LPS25HB #if MODULE_LPS331AP || MODULE_LPS25HB
#define TEMP_BASE (42.5f) #define TEMP_BASE (4250U) /* = 42.5 C */
#define TEMP_DIVIDER (480U) #define TEMP_DIVIDER (480U)
#else #else
#define TEMP_BASE (0.0f) #define TEMP_BASE (0U)
#define TEMP_DIVIDER (100U) #define TEMP_DIVIDER (100U)
#endif #endif
@ -128,8 +131,8 @@ int lpsxxx_init(lpsxxx_t *dev, const lpsxxx_params_t * params)
int lpsxxx_read_temp(const lpsxxx_t *dev, int16_t *temp) int lpsxxx_read_temp(const lpsxxx_t *dev, int16_t *temp)
{ {
uint8_t tmp; uint8_t tmp;
int16_t val = 0; int32_t val = 0;
float res = TEMP_BASE; /* reference value -> see datasheet */ uint16_t res = TEMP_BASE; /* reference value -> see datasheet */
i2c_acquire(DEV_I2C); i2c_acquire(DEV_I2C);
if (i2c_read_reg(DEV_I2C, DEV_ADDR, LPSXXX_REG_TEMP_OUT_L, &tmp, 0) < 0) { if (i2c_read_reg(DEV_I2C, DEV_ADDR, LPSXXX_REG_TEMP_OUT_L, &tmp, 0) < 0) {
@ -147,13 +150,15 @@ int lpsxxx_read_temp(const lpsxxx_t *dev, int16_t *temp)
i2c_release(DEV_I2C); i2c_release(DEV_I2C);
val |= ((uint16_t)tmp << 8); val |= ((uint16_t)tmp << 8);
DEBUG("[lpsxxx] read_temp: raw data %08" PRIx32 "\n", (uint32_t)val); DEBUG("[lpsxxx] read_temp: raw data %08" PRIx32 "\n", val);
/* compute actual temperature value in °C */ /* convert val to c°C */
res += ((float)val) / TEMP_DIVIDER; val *= 100;
/* return temperature in c°C */ /* compute actual temperature value in c°C */
*temp = (int16_t)(res * 100); res += DIV_ROUND(val, TEMP_DIVIDER);
*temp = res;
return LPSXXX_OK; return LPSXXX_OK;
} }