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cpu/nrf5x_common/periph_temperature: Increase resolution

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Modify the periph_temperature implementation to expose the full
resolution of the temperature sensor. The accuracy of the sensor will
likely be less than 0.25 °C, but typically temperature sensors have
a precision in the order of their resolution. Exposing the full
resolution can therefore be useful to monitor relative temperature
changes.
This commit is contained in:
Marian Buschsieweke 2021-12-14 22:46:33 +01:00
parent 0afed1de20
commit 8ee657f0e5
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GPG Key ID: CB8E3238CE715A94
1 changed files with 12 additions and 6 deletions
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18
cpu/nrf5x_common/periph/temperature.c
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@ -24,7 +24,11 @@
#include "saul_reg.h"
#include "phydat.h"
void temperature_read(int16_t *temp)
/**
* @brief Read the temperature in E-02 °C
* @return The measured temperature in E-02 °C (e.g. 1825 would mean 18.25 °C)
*/
static int16_t temperature_read(void)
{
/* Start temperature measurement task */
NRF_TEMP->TASKS_START = 1;
@ -32,22 +36,24 @@ void temperature_read(int16_t *temp)
/* Wait for temperature measurement to be ready */
while (!NRF_TEMP->EVENTS_DATARDY); /* takes 36us according to manual */
/* temperature is in 0.25°C step, so just divide by 4 */
*temp = (int16_t)NRF_TEMP->TEMP >> 2;
/* temperature is in 0.25°C step, multiply by 25 to convert to E-02 °C */
int32_t temp = NRF_TEMP->TEMP * 25;
/* Clear data ready bit and stop temperature measurement task */
NRF_TEMP->EVENTS_DATARDY = 0;
NRF_TEMP->TASKS_STOP = 1;
return temp;
}
static int _read_temperature(const void *dev, phydat_t *res)
{
(void) dev;
temperature_read(&res->val[0]);
(void)dev;
res->val[0] = temperature_read();
res->val[1] = 0;
res->val[2] = 0;
res->unit = UNIT_TEMP_C;
res->scale = 0;
res->scale = -2;
return 1;
}