drivers: sensor: Fixed issues in DHT20 measurement
Refactor DHT20 sensor init and measurement handling. Added 100ms power-on wait to comply with datasheet. Simplified measurement frame handling. Initialize status register only once after power-on. Signed-off-by: Konrad Sikora <kontakt@konradsikora.pl>
This commit is contained in:
Konrad Sikora
Benjamin Cabé
parent
e1f4181c29
commit
8959d2857d
1 changed files with 47 additions and 48 deletions
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@ -18,8 +18,7 @@
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#define DHT20_STATUS_MASK (BIT(0) | BIT(1))
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#define DHT20_STATUS_MASK_CHECK 0x18
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#define DHT20_STATUS_MASK_POLL_STATE 0x80
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#define DHT20_STATUS_MASK_CHECK 0x18
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#define DHT20_MASK_RESET_REGISTER 0xB0
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@ -38,16 +37,24 @@
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#define DHT20_RESET_REGISTER_1 0x1C
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#define DHT20_RESET_REGISTER_2 0x1E
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/** Length of the buffer used for data measurement */
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#define DHT20_MEASUREMENT_BUFFER_LENGTH 7
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/** Measurement frame data indexes */
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#define DHT20_MEAS_STATUS_IDX 0
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#define DHT20_MEAS_HUMIDITY_IDX 1
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#define DHT20_MEAS_HUM_TEMP_IDX 3
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#define DHT20_MEAS_TEMPERATURE_IDX 4
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#define DHT20_MEAS_CRC_IDX 6
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#define DHT20_MEAS_FRAME_LENGTH 7
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/** Wait some time after reset sequence (in ms) */
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#define DHT20_RESET_SEQUENCE_WAIT_MS 10
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#define DHT20_STATUS_BUSY_BIT BIT(7)
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#define DHT20_IS_STATUS_BUSY(status) ((status) & DHT20_STATUS_BUSY_BIT)
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/** Wait after power on (in ms) */
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#define DHT20_POWER_ON_WAIT_MS 75
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/** Wait during polling after power on (in ms) */
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#define DHT20_INIT_POLL_STATUS_WAIT_MS 5
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/** Wait some time after status reset sequence (in ms) */
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#define DHT20_STATUS_RESET_SEQUENCE_WAIT_MS 10
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/* According to datasheet 7.4: Wait time after power-on should be at least 100ms */
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#define DHT20_POWER_ON_WAIT_TIME_MS 100
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/** Wait for the measurement to be completed (in ms) */
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#define DHT20_MEASUREMENT_TIME_MS 80
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LOG_MODULE_REGISTER(DHT20, CONFIG_SENSOR_LOG_LEVEL);
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@ -75,15 +82,9 @@ static inline int read_status(const struct device *dev, uint8_t *status)
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uint8_t rx_buf[1];
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/* Write DHT20_STATUS_REGISTER then read to get status */
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rc = i2c_write_dt(&cfg->bus, tx_buf, sizeof(tx_buf));
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rc = i2c_write_read_dt(&cfg->bus, tx_buf, sizeof(tx_buf), &rx_buf, sizeof(rx_buf));
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if (rc < 0) {
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LOG_ERR("Failed to start measurement.");
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return rc;
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}
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rc = i2c_read_dt(&cfg->bus, rx_buf, sizeof(rx_buf));
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if (rc < 0) {
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LOG_ERR("Failed to read data from device.");
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LOG_ERR("Failed to read status register.");
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return rc;
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}
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@ -119,7 +120,7 @@ static inline int reset_register(const struct device *dev, uint8_t reg)
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return rc;
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}
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static inline int reset_sensor(const struct device *dev)
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static inline int initialize_status_register(const struct device *dev)
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{
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int rc;
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uint8_t status;
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@ -147,16 +148,15 @@ static inline int reset_sensor(const struct device *dev)
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if (rc < 0) {
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return rc;
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}
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/* Wait 10ms after reset sequence */
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k_msleep(DHT20_RESET_SEQUENCE_WAIT_MS);
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/* Wait 10ms after status reset sequence */
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k_msleep(DHT20_STATUS_RESET_SEQUENCE_WAIT_MS);
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}
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return 0;
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}
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static int dht20_read_sample(const struct device *dev, uint32_t *t_sample, uint32_t *rh_sample)
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static int dht20_read_sample(const struct dht20_config *cfg, struct dht20_data *data)
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{
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const struct dht20_config *cfg = dev->config;
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/*
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* Datasheet shows content of the measurement data as follow
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*
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@ -172,32 +172,36 @@ static int dht20_read_sample(const struct device *dev, uint32_t *t_sample, uint3
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* | 6 | CRC |
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* +------+----------------------------------------+
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*/
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uint8_t rx_buf[DHT20_MEASUREMENT_BUFFER_LENGTH];
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uint8_t rx_buf[DHT20_MEAS_FRAME_LENGTH];
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int rc;
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uint8_t status;
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rc = i2c_read_dt(&cfg->bus, rx_buf, sizeof(rx_buf));
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if (rc < 0) {
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LOG_ERR("Failed to read data from device.");
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LOG_ERR("Failed to read measurement frame.");
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return rc;
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}
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status = rx_buf[0];
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if (DHT20_IS_STATUS_BUSY(rx_buf[DHT20_MEAS_STATUS_IDX])) {
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LOG_WRN("Sensor measurement is not ready");
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return -EBUSY;
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}
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/* Extract 20 bits for humidity data */
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*rh_sample = sys_get_be24(&rx_buf[1]) >> 4;
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data->rh_sample = sys_get_be24(&rx_buf[DHT20_MEAS_HUMIDITY_IDX]) >> 4;
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/* Extract 20 bits for temperature data */
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*t_sample = sys_get_be24(&rx_buf[3]) & 0x0FFFFF;
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data->t_sample = sys_get_be24(&rx_buf[DHT20_MEAS_HUM_TEMP_IDX]) & 0x0FFFFF;
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#if defined(CONFIG_DHT20_CRC)
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/* Compute and check CRC with last byte of measurement data */
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uint8_t crc = crc8(rx_buf, 6, DHT20_CRC_POLYNOM, 0xFF, false);
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if (crc != rx_buf[6]) {
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rc = -EIO;
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if (crc != rx_buf[DHT20_MEAS_CRC_IDX]) {
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return -EIO;
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}
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#endif
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return rc;
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return 0;
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}
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static int dht20_sample_fetch(const struct device *dev, enum sensor_channel chan)
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@ -207,16 +211,12 @@ static int dht20_sample_fetch(const struct device *dev, enum sensor_channel chan
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int rc;
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uint8_t tx_buf[DHT20_TRIGGER_MEASUREMENT_BUFFER_LENGTH] = {
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DHT20_TRIGGER_MEASUREMENT_COMMAND};
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uint8_t status;
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if (chan != SENSOR_CHAN_ALL && chan != SENSOR_CHAN_AMBIENT_TEMP &&
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chan != SENSOR_CHAN_HUMIDITY) {
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return -ENOTSUP;
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}
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/* Reset sensor if needed */
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reset_sensor(dev);
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/* Send trigger measurement command */
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rc = i2c_write_dt(&cfg->bus, tx_buf, sizeof(tx_buf));
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if (rc < 0) {
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@ -228,19 +228,9 @@ static int dht20_sample_fetch(const struct device *dev, enum sensor_channel chan
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* According to datasheet maximum time to make temperature and humidity
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* measurements is 80ms
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*/
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k_msleep(DHT20_POWER_ON_WAIT_MS);
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k_msleep(DHT20_MEASUREMENT_TIME_MS);
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do {
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k_msleep(DHT20_INIT_POLL_STATUS_WAIT_MS);
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rc = read_status(dev, &status);
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if (rc < 0) {
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LOG_ERR("Failed to read status.");
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return rc;
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}
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} while ((status & DHT20_STATUS_MASK_POLL_STATE) != 0);
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rc = dht20_read_sample(dev, &data->t_sample, &data->rh_sample);
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rc = dht20_read_sample(cfg, data);
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if (rc < 0) {
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LOG_ERR("Failed to fetch data.");
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return rc;
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@ -298,12 +288,21 @@ static int dht20_channel_get(const struct device *dev, enum sensor_channel chan,
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static int dht20_init(const struct device *dev)
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{
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const struct dht20_config *cfg = dev->config;
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int rc;
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if (!i2c_is_ready_dt(&cfg->bus)) {
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LOG_ERR("I2C dev %s not ready", cfg->bus.bus->name);
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return -ENODEV;
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}
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k_msleep(DHT20_POWER_ON_WAIT_TIME_MS);
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rc = initialize_status_register(dev);
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if (rc < 0) {
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LOG_ERR("Failed to initialize status register.");
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return rc;
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}
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return 0;
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}
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