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drivers: sensor: Fixed issues in DHT20 measurement

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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 2024-08-04 20:57:25 +02:00 • committed by Benjamin Cabé
commit 8959d2857d
1 changed files with 47 additions and 48 deletions
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95
drivers/sensor/aosong/dht20/dht20.c
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@ -18,8 +18,7 @@
#define DHT20_STATUS_MASK (BIT(0) | BIT(1)) #define DHT20_STATUS_MASK (BIT(0) | BIT(1))
#define DHT20_STATUS_MASK_CHECK 0x18 #define DHT20_STATUS_MASK_CHECK 0x18
#define DHT20_STATUS_MASK_POLL_STATE 0x80
#define DHT20_MASK_RESET_REGISTER 0xB0 #define DHT20_MASK_RESET_REGISTER 0xB0
@ -38,16 +37,24 @@
#define DHT20_RESET_REGISTER_1 0x1C #define DHT20_RESET_REGISTER_1 0x1C
#define DHT20_RESET_REGISTER_2 0x1E #define DHT20_RESET_REGISTER_2 0x1E
/** Length of the buffer used for data measurement */ /** Measurement frame data indexes */
#define DHT20_MEASUREMENT_BUFFER_LENGTH 7 #define DHT20_MEAS_STATUS_IDX 0
#define DHT20_MEAS_HUMIDITY_IDX 1
#define DHT20_MEAS_HUM_TEMP_IDX 3
#define DHT20_MEAS_TEMPERATURE_IDX 4
#define DHT20_MEAS_CRC_IDX 6
#define DHT20_MEAS_FRAME_LENGTH 7
/** Wait some time after reset sequence (in ms) */ #define DHT20_STATUS_BUSY_BIT BIT(7)
#define DHT20_RESET_SEQUENCE_WAIT_MS 10 #define DHT20_IS_STATUS_BUSY(status) ((status) & DHT20_STATUS_BUSY_BIT)
/** Wait after power on (in ms) */ /** Wait some time after status reset sequence (in ms) */
#define DHT20_POWER_ON_WAIT_MS 75 #define DHT20_STATUS_RESET_SEQUENCE_WAIT_MS 10
/** Wait during polling after power on (in ms) */
#define DHT20_INIT_POLL_STATUS_WAIT_MS 5 /* According to datasheet 7.4: Wait time after power-on should be at least 100ms */
#define DHT20_POWER_ON_WAIT_TIME_MS 100
/** Wait for the measurement to be completed (in ms) */
#define DHT20_MEASUREMENT_TIME_MS 80
LOG_MODULE_REGISTER(DHT20, CONFIG_SENSOR_LOG_LEVEL); LOG_MODULE_REGISTER(DHT20, CONFIG_SENSOR_LOG_LEVEL);
@ -75,15 +82,9 @@ static inline int read_status(const struct device *dev, uint8_t *status)
uint8_t rx_buf[1]; uint8_t rx_buf[1];
/* Write DHT20_STATUS_REGISTER then read to get status */ /* Write DHT20_STATUS_REGISTER then read to get status */
rc = i2c_write_dt(&cfg->bus, tx_buf, sizeof(tx_buf)); rc = i2c_write_read_dt(&cfg->bus, tx_buf, sizeof(tx_buf), &rx_buf, sizeof(rx_buf));
if (rc < 0) { if (rc < 0) {
LOG_ERR("Failed to start measurement."); LOG_ERR("Failed to read status register.");
return rc;
}
rc = i2c_read_dt(&cfg->bus, rx_buf, sizeof(rx_buf));
if (rc < 0) {
LOG_ERR("Failed to read data from device.");
return rc; return rc;
} }
@ -119,7 +120,7 @@ static inline int reset_register(const struct device *dev, uint8_t reg)
return rc; return rc;
} }
static inline int reset_sensor(const struct device *dev) static inline int initialize_status_register(const struct device *dev)
{ {
int rc; int rc;
uint8_t status; uint8_t status;
@ -147,16 +148,15 @@ static inline int reset_sensor(const struct device *dev)
if (rc < 0) { if (rc < 0) {
return rc; return rc;
} }
/* Wait 10ms after reset sequence */ /* Wait 10ms after status reset sequence */
k_msleep(DHT20_RESET_SEQUENCE_WAIT_MS); k_msleep(DHT20_STATUS_RESET_SEQUENCE_WAIT_MS);
} }
return 0; return 0;
} }
static int dht20_read_sample(const struct device *dev, uint32_t *t_sample, uint32_t *rh_sample) static int dht20_read_sample(const struct dht20_config *cfg, struct dht20_data *data)
{ {
const struct dht20_config *cfg = dev->config;
/* /*
* Datasheet shows content of the measurement data as follow * Datasheet shows content of the measurement data as follow
* *
@ -172,32 +172,36 @@ static int dht20_read_sample(const struct device *dev, uint32_t *t_sample, uint3
* | 6 | CRC | * | 6 | CRC |
* +------+----------------------------------------+ * +------+----------------------------------------+
*/ */
uint8_t rx_buf[DHT20_MEASUREMENT_BUFFER_LENGTH];
uint8_t rx_buf[DHT20_MEAS_FRAME_LENGTH];
int rc; int rc;
uint8_t status;
rc = i2c_read_dt(&cfg->bus, rx_buf, sizeof(rx_buf)); rc = i2c_read_dt(&cfg->bus, rx_buf, sizeof(rx_buf));
if (rc < 0) { if (rc < 0) {
LOG_ERR("Failed to read data from device."); LOG_ERR("Failed to read measurement frame.");
return rc; return rc;
} }
status = rx_buf[0]; if (DHT20_IS_STATUS_BUSY(rx_buf[DHT20_MEAS_STATUS_IDX])) {
LOG_WRN("Sensor measurement is not ready");
return -EBUSY;
}
/* Extract 20 bits for humidity data */ /* Extract 20 bits for humidity data */
*rh_sample = sys_get_be24(&rx_buf[1]) >> 4; data->rh_sample = sys_get_be24(&rx_buf[DHT20_MEAS_HUMIDITY_IDX]) >> 4;
/* Extract 20 bits for temperature data */ /* Extract 20 bits for temperature data */
*t_sample = sys_get_be24(&rx_buf[3]) & 0x0FFFFF; data->t_sample = sys_get_be24(&rx_buf[DHT20_MEAS_HUM_TEMP_IDX]) & 0x0FFFFF;
#if defined(CONFIG_DHT20_CRC) #if defined(CONFIG_DHT20_CRC)
/* Compute and check CRC with last byte of measurement data */ /* Compute and check CRC with last byte of measurement data */
uint8_t crc = crc8(rx_buf, 6, DHT20_CRC_POLYNOM, 0xFF, false); uint8_t crc = crc8(rx_buf, 6, DHT20_CRC_POLYNOM, 0xFF, false);
if (crc != rx_buf[6]) { if (crc != rx_buf[DHT20_MEAS_CRC_IDX]) {
rc = -EIO; return -EIO;
} }
#endif #endif
return rc; return 0;
} }
static int dht20_sample_fetch(const struct device *dev, enum sensor_channel chan) static int dht20_sample_fetch(const struct device *dev, enum sensor_channel chan)
@ -207,16 +211,12 @@ static int dht20_sample_fetch(const struct device *dev, enum sensor_channel chan
int rc; int rc;
uint8_t tx_buf[DHT20_TRIGGER_MEASUREMENT_BUFFER_LENGTH] = { uint8_t tx_buf[DHT20_TRIGGER_MEASUREMENT_BUFFER_LENGTH] = {
DHT20_TRIGGER_MEASUREMENT_COMMAND}; DHT20_TRIGGER_MEASUREMENT_COMMAND};
uint8_t status;
if (chan != SENSOR_CHAN_ALL && chan != SENSOR_CHAN_AMBIENT_TEMP && if (chan != SENSOR_CHAN_ALL && chan != SENSOR_CHAN_AMBIENT_TEMP &&
chan != SENSOR_CHAN_HUMIDITY) { chan != SENSOR_CHAN_HUMIDITY) {
return -ENOTSUP; return -ENOTSUP;
} }
/* Reset sensor if needed */
reset_sensor(dev);
/* Send trigger measurement command */ /* Send trigger measurement command */
rc = i2c_write_dt(&cfg->bus, tx_buf, sizeof(tx_buf)); rc = i2c_write_dt(&cfg->bus, tx_buf, sizeof(tx_buf));
if (rc < 0) { if (rc < 0) {
@ -228,19 +228,9 @@ static int dht20_sample_fetch(const struct device *dev, enum sensor_channel chan
* According to datasheet maximum time to make temperature and humidity * According to datasheet maximum time to make temperature and humidity
* measurements is 80ms * measurements is 80ms
*/ */
k_msleep(DHT20_POWER_ON_WAIT_MS); k_msleep(DHT20_MEASUREMENT_TIME_MS);
do { rc = dht20_read_sample(cfg, data);
k_msleep(DHT20_INIT_POLL_STATUS_WAIT_MS);
rc = read_status(dev, &status);
if (rc < 0) {
LOG_ERR("Failed to read status.");
return rc;
}
} while ((status & DHT20_STATUS_MASK_POLL_STATE) != 0);
rc = dht20_read_sample(dev, &data->t_sample, &data->rh_sample);
if (rc < 0) { if (rc < 0) {
LOG_ERR("Failed to fetch data."); LOG_ERR("Failed to fetch data.");
return rc; return rc;
@ -298,12 +288,21 @@ static int dht20_channel_get(const struct device *dev, enum sensor_channel chan,
static int dht20_init(const struct device *dev) static int dht20_init(const struct device *dev)
{ {
const struct dht20_config *cfg = dev->config; const struct dht20_config *cfg = dev->config;
int rc;
if (!i2c_is_ready_dt(&cfg->bus)) { if (!i2c_is_ready_dt(&cfg->bus)) {
LOG_ERR("I2C dev %s not ready", cfg->bus.bus->name); LOG_ERR("I2C dev %s not ready", cfg->bus.bus->name);
return -ENODEV; return -ENODEV;
} }
k_msleep(DHT20_POWER_ON_WAIT_TIME_MS);
rc = initialize_status_register(dev);
if (rc < 0) {
LOG_ERR("Failed to initialize status register.");
return rc;
}
return 0; return 0;
} }