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SHT3x driver - some minor changes

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- lookup tables made const to be held in flash
- crc8 computation changed to a non table lookup version
- measurement duration is now given in ticks and can be used directly
  for vTaskDelay (documentation and examples changed accordingly)
This commit is contained in:
Gunar Schorcht 2017-10-13 17:43:43 +02:00
parent 5a0fc09989
commit 1525f61fe3
5 changed files with 55 additions and 73 deletions
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45
extras/sht3x/sht3x.h
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@ -137,7 +137,7 @@ typedef struct {
sht3x_repeat_t repeatability; // used repeatability
bool meas_started; // indicates whether measurement started
uint32_t meas_start_time; // measurement start time in microseconds
TickType_t meas_start_tick; // measurement start time in RTOS ticks
bool meas_first; // first measurement in periodic mode
} sht3x_sensor_t;
@ -161,28 +161,31 @@ sht3x_sensor_t* sht3x_init_sensor (uint8_t bus, uint8_t addr);
* @brief Start single shot or periodic measurements
*
* The function starts the measurement either in *single shot mode*
* (exactly one measurement) or *periodic mode* (periodic measurements).
* (exactly one measurement) or *periodic mode* (periodic measurements) and
* returns an estimated measurement duration given in RTOS ticks.
*
* In the *single shot mode*, this function has to be called for each
* measurement. The measurement duration returned by the function has to be
* waited every time before the results can be fetched.
*
* In the *periodic mode*, this function has to be called only once. Also the
* measurement duration must be waited only once until the first results are
* available. After this first measurement, the sensor then automatically
* performs all subsequent measurements. The rate of periodic measurements can
* be 10, 4, 2, 1 or 0.5 measurements per second (mps). The user task can
* fetch the results with the half or less rate. The rate of the periodic
* measurements is defined by the parameter *mode*.
* In the *periodic mode*, this function has to be called only once. Also
* the measurement duration must be waited only once until the first
* results are available. After this first measurement, the sensor then
* automatically performs all subsequent measurements. The rate of periodic
* measurements can be 10, 4, 2, 1 or 0.5 measurements per second (mps). Due
* to inaccuracies in timing of the sensor, the user task should fetch the
* results at a lower rate. The rate of the periodic measurements is defined
* by the parameter *mode*.
*
* On success, the function returns an estimated measurement duration. This
* defines the duration needed by the sensor before first results become
* available. The user task has to wait this time before it can fetch the
* results using function *sht3x_get_results* or *sht3x_get_raw_data*.
* On success, the function returns an estimated measurement duration given
* in RTOS ticks. This defines the duration needed by the sensor before
* first results become available. The user task has to wait this time
* before it can fetch the results using function *sht3x_get_results* or
* *sht3x_get_raw_data*.
*
* @param dev pointer to sensor device data structure
* @param mode measurement mode, see type *sht3x_mode_t*
* @return true on success, false on error
* @param dev pointer to sensor device data structure
* @param mode measurement mode, see type *sht3x_mode_t*
* @return measurement duration in RTOS ticks or -1 on error
*/
int32_t sht3x_start_measurement (sht3x_sensor_t* dev, sht3x_mode_t mode);
@ -190,9 +193,9 @@ int32_t sht3x_start_measurement (sht3x_sensor_t* dev, sht3x_mode_t mode);
/**
* @brief Check whether measurement is still running
*
* The function can be used to test whether a measurement has been started
* at all and how long it still takes before measurement results become
* available. The return value can be
* The function can be used to test whether a measurement has been
* started and how long it still takes before measurement results
* become available. The return value is given in RTOS ticks and can be
*
* >0 in case the measurement is is still running,
* 0 in case the measurement has been already finished, or
@ -201,8 +204,8 @@ int32_t sht3x_start_measurement (sht3x_sensor_t* dev, sht3x_mode_t mode);
* That is, a return value greater than 0 indicates that the measurement
* results are still not available and the user task has to wait that time.
*
* @param dev pointer to sensor device data structure
* @return remaining measurement duration or -1 on error
* @param dev pointer to sensor device data structure
* @return remaining measurement duration in RTOS ticks or -1 on error
*/
int32_t sht3x_is_measuring (sht3x_sensor_t* dev);