8fd4d7222a
The only change from v1 is how the temperature is encoded. In v2, two bytes at offset 4 and 5 represent a 16-bit signed int (in big-endian). It contains the temperature in degrees Celsius * 100. Fixes #29
70 lines
No EOL
1.9 KiB
C
70 lines
No EOL
1.9 KiB
C
#include "prst/shtc3.h"
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#include <app_error.h>
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#include <nrf_delay.h>
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#include <nrf_drv_twi.h>
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#include <nrf_log.h>
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#include <nrf_log_ctrl.h>
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#include "prst_config.h"
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static const nrf_drv_twi_t twi_ = NRF_DRV_TWI_INSTANCE(0);
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static nrf_drv_twi_config_t twi_config_ = NRF_DRV_TWI_DEFAULT_CONFIG;
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static uint8_t buff[6];
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static void write_cmd(uint16_t command) {
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uint8_t cmd[2];
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cmd[0] = command >> 8;
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cmd[1] = command & 0xff;
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APP_ERROR_CHECK(nrf_drv_twi_tx(&twi_, PRST_SHTC3_ADDR, cmd, 2,
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/*no_stop=*/false));
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}
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void prst_shtc3_init() {
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twi_config_.scl = PRST_SHT3C_SCL_PIN;
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twi_config_.sda = PRST_SHT3C_SDA_PIN;
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twi_config_.frequency = NRF_TWI_FREQ_100K;
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}
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prst_shtc3_read_t prst_shtc3_read() {
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APP_ERROR_CHECK(nrf_drv_twi_init(&twi_, &twi_config_, NULL, NULL));
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nrf_drv_twi_enable(&twi_);
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// Wake the sensor up.
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write_cmd(PRST_SHTC3_CMD_WAKEUP);
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nrf_delay_ms(1);
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// Request measurement.
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write_cmd(PRST_SHTC3_CMD_MEASURE_TFIRST_NORMAL);
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// Reading in normal (not low power) mode can take up to 12.1 ms, according to
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// the datasheet.
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nrf_delay_ms(15);
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// Read temp and humidity.
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while (nrf_drv_twi_rx(&twi_, PRST_SHTC3_ADDR, buff, 6) != 0) {
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nrf_delay_ms(10);
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}
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// Put the sensor in sleep mode.
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write_cmd(PRST_SHTC3_CMD_SLEEP);
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// Uninit i2c.
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nrf_drv_twi_uninit(&twi_);
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// TODO(rbaron): verify the CRC of the measurements. The function is described
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// in the datasheet.
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float temp_c = -45 + 175 * ((float)((buff[0] << 8) | buff[1])) / (1 << 16);
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uint16_t humi = (buff[3] << 8) | buff[4];
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prst_shtc3_read_t ret = {.temp_celsius = temp_c, .humidity = humi};
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#if PRST_SHT3C_DEBUG
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NRF_LOG_INFO("[sht3c] Read temp: " NRF_LOG_FLOAT_MARKER " oC",
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NRF_LOG_FLOAT((float)ret.temp_celsius));
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NRF_LOG_INFO("[sht3c] Read humi: " NRF_LOG_FLOAT_MARKER " %%",
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NRF_LOG_FLOAT(100.0 * ret.humidity / 0xffff));
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#endif
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return ret;
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} |