data caching removed

RIOT-OS · Jun 13, 2023 · 645ea94 · 645ea94
1 parent e62c6b8
commit 645ea94
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Showing 3 changed files with 27 additions and 64 deletions.
diff --git a/drivers/dht/dht.c b/drivers/dht/dht.c
@@ -44,9 +44,6 @@
 #define READ_THRESHOLD          (40U)
 /* If an expected pulse is not detected within 85µs, something is wrong */
 #define SPIN_TIMEOUT            (85U)
-/* According to datasheet the DHT sensor cannot measure more than once
- * every 2 seconds but most are faster */
-#define RESPAWN_TIMEOUT         (2U * US_PER_SEC)
 /* The start signal by pulling data low for at least 18 ms for DHT11, at
  * most 20 ms (AM2301 / DHT22 / DHT21). Then release the bus and the
  * sensor should respond by pulling data low for 80 µs, then release for
@@ -238,68 +235,36 @@ int dht_read(dht_t *dev, int16_t *temp, int16_t *hum)
 {
     assert(dev);
 
-    bool first_read = 0;
-    if (!dev->data_hold_time) {
-        first_read = 1;
-        uint16_t timeout = RESPAWN_TIMEOUT / US_PER_MS;
-        while (_send_start_signal(dev) == -ENODEV
-            && (timeout -= START_LOW_TIME / US_PER_MS) > 0) {}
-    }
-
-    uint32_t now_us = ztimer_now(ZTIMER_USEC);
-    if ((now_us - dev->last_read_us) > dev->data_hold_time) {
-        dev->last_read_us = now_us;
-        struct dht_data data = {
-            .pin = dev->params.pin,
-            .in_mode = dev->params.in_mode,
-            .bit_pos = 0,
-        };
+    struct dht_data data = {
+        .pin = dev->params.pin,
+        .in_mode = dev->params.in_mode,
+        .bit_pos = 0,
+    };
 
-        if (first_read) {
-            uint16_t timeout = RESPAWN_TIMEOUT / US_PER_MS;
-            while (_send_start_signal(dev) == -ENODEV
-                && (timeout -= START_LOW_TIME / US_PER_MS) > 0) {}
-            dev->last_read_us = ztimer_now(ZTIMER_USEC);
-            dev->data_hold_time = (dev->last_read_us - now_us);
-            /* DEBUG() delayed after _busy_wait_read() */
-        }
-        else if (_send_start_signal(dev) == -ENODEV) {
-            DEBUG_PUTS("[dht] error: No response from device, "
-                        "insufficient RESPAWN_TIMEOUT?");
-            DEBUG("[dht] data_hold_time = %" PRIu32 " µs\n", dev->data_hold_time);
-            return -ENODEV;
-        }
-
-        /* read the data */
-        _busy_wait_read(&data);
-
-        if (first_read) {
-             DEBUG("[dht] first read, set data_hold_time to: %" PRIu32 " ms\n",
-                    (uint32_t)(dev->data_hold_time / US_PER_MS));
-        }
+    if (_send_start_signal(dev) == -ENODEV) {
+        DEBUG_PUTS("[dht] error: No response from device");
+        return -ENODEV;
+    }
 
-        if (_validate_checksum(data.data) == -EIO) {
-            DEBUG("[dht] error: checksum doesn't match\n"
-                  "[dht] RAW data: 0x%02x, 0x%02x, 0x%02x, 0x%02x, 0x%02x\n",
-                  (unsigned)data.data[0], (unsigned)data.data[1],
-                  (unsigned)data.data[2], (unsigned)data.data[3],
-                  (unsigned)data.data[4]);
-            return -EIO;
-        }
+    /* read the data */
+    _busy_wait_read(&data);
 
-        if (_parse_raw_values(dev, data.data) == -ENOSYS) {
-            DEBUG_PUTS("[dht] error: data format not implemented");
-            return -ENOSYS;
-        }
+    if (_validate_checksum(data.data) == -EIO) {
+        DEBUG("[dht] error: checksum doesn't match\n"
+              "[dht] RAW data: 0x%02x, 0x%02x, 0x%02x, 0x%02x, 0x%02x\n",
+              (unsigned)data.data[0], (unsigned)data.data[1],
+              (unsigned)data.data[2], (unsigned)data.data[3],
+              (unsigned)data.data[4]);
+        return -EIO;
     }
 
-    if (temp) {
-        *temp = dev->last_val.temperature;
+    if (_parse_raw_values(dev, data.data) == -ENOSYS) {
+        DEBUG_PUTS("[dht] error: data format not implemented");
+        return -ENOSYS;
     }
 
-    if (hum) {
-        *hum = dev->last_val.humidity;
-    }
+    *hum = dev->last_val.humidity;
+    *temp = dev->last_val.temperature;
 
     return 0;
 }
diff --git a/drivers/include/dht.h b/drivers/include/dht.h
@@ -55,7 +55,7 @@ enum {
  * @brief   Data type for storing DHT sensor readings
  */
 typedef struct {
-    uint16_t humidity;      /**< relative percent */
+    uint16_t humidity;      /**< relative humidity in deci-percent */
     uint16_t temperature;   /**< temperature in deci-Celsius */
 } dht_data_t;
 
@@ -87,8 +87,6 @@ typedef struct {
 typedef struct {
     dht_params_t params;    /**< Device parameters */
     dht_data_t last_val;    /**< Values of the last measurement */
-    uint32_t last_read_us;  /**< Time of the last measurement */
-    uint32_t data_hold_time;/**< Measured minimal data hold time */
 } dht_t;
 
 /**

diff --git a/tests/drivers/dht/main.c b/tests/drivers/dht/main.c
@@ -28,7 +28,7 @@
 #include "time_units.h"
 #include "ztimer.h"
 
-#define DELAY           (500 * US_PER_MS)
+#define DELAY           (2 * US_PER_SEC)
 
 int main(void)
 {
@@ -49,15 +49,15 @@ int main(void)
 
     /* periodically read temp and humidity values */
     while (1) {
+        ztimer_sleep(ZTIMER_USEC, DELAY);
+
         if (dht_read(&dev, &temp, &hum) != DHT_OK) {
             puts("Error reading values");
             continue;
         }
 
         printf("DHT values - temp: %d.%d°C - relative humidity: %d.%d%%\n",
                temp/10, temp%10, hum/10, hum%10);
-
-        ztimer_sleep(ZTIMER_USEC, DELAY);
     }
 
     return 0;