135 lines
3.1 KiB
C
135 lines
3.1 KiB
C
#include <stddef.h>
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/* Private header */
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#include "aht10.h"
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#define AHT10_STATUS_CALIBRATED_MASK (1U << 3U)
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#define AHT10_STATUS_BUSY_MASK (1U << 7U)
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#define AHT10_ERROR_CHECK(x) \
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if (x != AHT10_OK) return AHT10_FAIL
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typedef struct {
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uint8_t status;
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uint32_t temperature;
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uint32_t humidity;
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} aht10_raw_t;
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static aht10_ret_t aht10_software_reset(aht10_t *aht) {
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/* Reset and initialize device */
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uint8_t tx_data[3] = {0xBA};
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aht10_xfer_desc_t xfer = {
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.tx_data = tx_data,
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.tx_size = 1U,
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.rx_data = NULL,
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.rx_size = 0U,
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};
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AHT10_ERROR_CHECK(aht->cb.xfer(aht->user_data, &xfer));
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AHT10_ERROR_CHECK(aht->cb.delay(aht->user_data, 20));
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tx_data[0] = 0xE1;
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tx_data[1] = 0x08;
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tx_data[2] = 0x00;
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xfer.tx_size = 3U;
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AHT10_ERROR_CHECK(aht->cb.xfer(aht->user_data, &xfer));
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return AHT10_OK;
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}
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static aht10_ret_t aht10_start_measurement(aht10_t *aht) {
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/* Start measurement */
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uint8_t tx_data[3] = {0xAC, 0x33, 0x00};
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aht10_xfer_desc_t xfer = {
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.tx_data = tx_data,
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.tx_size = 3U,
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.rx_data = NULL,
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.rx_size = 0U,
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};
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AHT10_ERROR_CHECK(aht->cb.xfer(aht->user_data, &xfer));
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return AHT10_OK;
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}
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static aht10_ret_t aht10_read_result(aht10_t *aht, aht10_raw_t *raw) {
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/* Read conversion result */
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uint8_t tx_data[] = {0x71};
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uint8_t rx_data[6];
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aht10_xfer_desc_t xfer = {
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.tx_data = tx_data,
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.tx_size = 1U,
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.rx_data = rx_data,
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.rx_size = 6U,
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};
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AHT10_ERROR_CHECK(aht->cb.xfer(aht->user_data, &xfer));
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raw->humidity = rx_data[1] << 12U;
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raw->humidity |= rx_data[2] << 4U;
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raw->humidity |= rx_data[3] >> 4U;
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raw->temperature = (rx_data[3] & 0x0FU) << 16U;
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raw->temperature |= rx_data[4] << 8U;
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raw->temperature |= rx_data[5];
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raw->status = rx_data[0];
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return AHT10_OK;
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}
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aht10_ret_t aht10_init(aht10_t *aht) {
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/* Check if we need initialization */
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/* Delay 40ms after POR */
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AHT10_ERROR_CHECK(aht->cb.delay(aht->user_data, 40));
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aht10_raw_t raw;
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/* Check 0x71 status byte, if uncalibrated then reset and calibrate it. */
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AHT10_ERROR_CHECK(aht10_read_result(aht, &raw));
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if ((raw.status & AHT10_STATUS_CALIBRATED_MASK) == 0) {
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AHT10_ERROR_CHECK(aht10_software_reset(aht));
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}
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return AHT10_OK;
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}
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aht10_ret_t aht10_measure(aht10_t *aht, aht10_result_t *result) {
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/* Start a measurement and read back result... */
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AHT10_ERROR_CHECK(aht10_start_measurement(aht));
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AHT10_ERROR_CHECK(aht->cb.delay(aht->user_data, 80));
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aht10_raw_t raw;
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uint8_t max_retries = 5U;
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do {
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AHT10_ERROR_CHECK(aht10_read_result(aht, &raw));
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max_retries--;
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if (max_retries == 0) {
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return AHT10_FAIL;
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}
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#ifndef AHT10_SKIP_BUSY_CHECK
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} while (raw.status & AHT10_STATUS_BUSY_MASK);
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#else
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} while (0);
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#endif
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result->temperature = ((double)raw.temperature * 200.0 / 1048576.0) - 50.0;
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result->humidity = (double)raw.humidity * 100.0 / 1048576.0;
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return AHT10_OK;
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}
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