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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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13
extras/sht3x/README.md
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@ -119,7 +119,7 @@ void user_task (void *pvParameters)
// passive waiting until first measurement results are available
if (duration > 0)
vTaskDelay (duration/portTICK_PERIOD_MS);
vTaskDelay (duration);
// busy waiting until first measurement results are available
// while (sht3x_is_measuring (sensor) > 0) ;
@ -140,7 +140,7 @@ void user_task (void *pvParameters)
}
```
At the beginning of the task, the periodic measurement is started by function **_sht3x_start_measurement_** with a rate of 1 measurement per second. Using the measurement duration returned from this function, the task is delayed using **_vTaskDelay_** to wait for first measurement results. The busy waiting alternative using function **_sht3x_is_measuring_** is shown in comments. Inside the task loop, the measurement results are fetched periodically using function **_sht3x_get_results_** with a rate of once per second.
At the beginning of the task, the periodic measurement is started by function **_sht3x_start_measurement_** with a rate of 1 measurement per second. Using the measurement duration in RTOS ticks returned from this function, the task is delayed using **_vTaskDelay_** to wait for first measurement results. The busy waiting alternative using function **_sht3x_is_measuring_** is shown in comments. Inside the task loop, the measurement results are fetched periodically using function **_sht3x_get_results_** with a rate of once per second.
In the **single shot mode**, the measurement has to be triggered
in each cycle. Waiting for measurement results is also required in each cylce, before the results can be fetched.
@ -162,7 +162,7 @@ void user_task (void *pvParameters)
// passive waiting until measurement results are available
if (duration > 0)
vTaskDelay (duration/portTICK_PERIOD_MS);
vTaskDelay (duration);
// busy waiting until first measurement results are available
// while (sht3x_is_measuring (sensor) > 0) ;
@ -233,7 +233,7 @@ static sht3x_sensor_t* sensor; // sensor device data structure
/*
* User task that fetches latest measurement results of sensor every 2
* seconds. It starts the SHT3x in periodic mode with 1 measurements per
* second (*periodic_1mps*). It uses busy waiting for first measurement
* second (*periodic_1mps*). It uses passive waiting for first measurement
* results.
*/
void user_task (void *pvParameters)
@ -242,9 +242,10 @@ void user_task (void *pvParameters)
// start periodic measurements with 1 measurement per second
sht3x_start_measurement (sensor, periodic_1mps);
// passive waiting until measurement results are available
if (duration > 0)
vTaskDelay (duration/portTICK_PERIOD_MS);
vTaskDelay (duration);
TickType_t last_wakeup = xTaskGetTickCount();