Updated Drivers

drivers/0x09_dht11/0x09_dht11.c

@@ -45,24 +45,37 @@
 
 #define DHT11_GPIO 4
 
+
+/**
+ * @brief Read the DHT11 sensor and print the result over UART
+ *
+ * Attempts a single read. On success prints humidity and temperature;
+ * on failure prints a wiring-check message. Waits 2 s before returning
+ * to respect the DHT11 minimum polling interval.
+ */
+static void _print_reading(void) {
+    float humidity = 0.0f;
+    float temperature = 0.0f;
+    if (dht11_read(&humidity, &temperature))
+        printf("Humidity: %.1f%%  Temperature: %.1f C\r\n", humidity, temperature);
+    else
+        printf("DHT11 read failed - check wiring on GPIO %d\r\n", DHT11_GPIO);
+    sleep_ms(2000);
+}
+
+
+/**
+ * @brief Application entry point for the DHT11 sensor demo
+ *
+ * Initializes the DHT11 on GPIO4 and continuously reads temperature
+ * and humidity, printing results over UART every 2 seconds.
+ *
+ * @return int Does not return
+ */
 int main(void) {
     stdio_init_all();
     dht11_init(DHT11_GPIO);
-
     printf("DHT11 driver initialized on GPIO %d\r\n", DHT11_GPIO);
-
-    while (true) {
-        float humidity    = 0.0f;
-        float temperature = 0.0f;
-
-        if (dht11_read(&humidity, &temperature)) {
-            printf("Humidity: %.1f%%  Temperature: %.1f C\r\n",
-                   humidity, temperature);
-        } else {
-            printf("DHT11 read failed - check wiring on GPIO %d\r\n",
-                   DHT11_GPIO);
-        }
-
-        sleep_ms(2000);
-    }
+    while (true)
+        _print_reading();
 }

drivers/0x09_dht11/dht11.c

@@ -33,46 +33,114 @@
 
 static uint dht_pin;
 
-void dht11_init(uint8_t pin) {
-    dht_pin = pin;
-    gpio_init(pin);
-    gpio_pull_up(pin);
-}
 
-bool dht11_read(float *humidity, float *temperature) {
-    uint8_t data[5] = {0};
-    
-    // Start signal
+/**
+ * @brief Send the DHT11 start signal on the data pin
+ *
+ * Drives the pin LOW for 18 ms then HIGH for 40 us before switching
+ * the pin to input mode to listen for the sensor response.
+ */
+static void _send_start_signal(void) {
     gpio_set_dir(dht_pin, GPIO_OUT);
     gpio_put(dht_pin, 0);
     sleep_ms(18);
     gpio_put(dht_pin, 1);
     sleep_us(40);
     gpio_set_dir(dht_pin, GPIO_IN);
-    
-    // Wait for response
+}
+
+
+/**
+ * @brief Wait for the pin to leave a given logic level
+ *
+ * Spins until the pin no longer reads the specified level, returning
+ * false if a timeout of 10 000 iterations is exceeded.
+ *
+ * @param level Logic level to wait through (0 or 1)
+ * @return bool true once the level changed, false on timeout
+ */
+static bool _wait_for_level(int level) {
     uint32_t timeout = 10000;
-    while (gpio_get(dht_pin) == 1) if (--timeout == 0) return false;
-    timeout = 10000;
-    while (gpio_get(dht_pin) == 0) if (--timeout == 0) return false;
-    timeout = 10000;
-    while (gpio_get(dht_pin) == 1) if (--timeout == 0) return false;
-    
-    // Read 40 bits
-    for (int i = 0; i < 40; i++) {
-        timeout = 10000;
-        while (gpio_get(dht_pin) == 0) if (--timeout == 0) return false;
-        uint32_t start = time_us_32();
-        timeout = 10000;
-        while (gpio_get(dht_pin) == 1) if (--timeout == 0) return false;
-        uint32_t duration = time_us_32() - start;
-        data[i / 8] <<= 1;
-        if (duration > 40) data[i / 8] |= 1;
-    }
-    
-    // Check checksum
-    if (data[4] != ((data[0] + data[1] + data[2] + data[3]) & 0xFF)) return false;
-    
+    while (gpio_get(dht_pin) == level)
+        if (--timeout == 0) return false;
+    return true;
+}
+
+
+/**
+ * @brief Wait for the DHT11 response after the start signal
+ *
+ * The sensor pulls LOW then HIGH then LOW again; each transition
+ * is awaited with a timeout.
+ *
+ * @return bool true if the full response was received, false on timeout
+ */
+static bool _wait_response(void) {
+    if (!_wait_for_level(1)) return false;
+    if (!_wait_for_level(0)) return false;
+    if (!_wait_for_level(1)) return false;
+    return true;
+}
+
+
+/**
+ * @brief Read a single bit from the DHT11 data stream
+ *
+ * Waits for the low-period to end, measures the high-period duration,
+ * and shifts the result into the appropriate byte of the data array.
+ *
+ * @param data 5-byte array accumulating the received bits
+ * @param i    Bit index (0-39)
+ * @return bool true on success, false on timeout
+ */
+static bool _read_bit(uint8_t *data, int i) {
+    if (!_wait_for_level(0)) return false;
+    uint32_t start = time_us_32();
+    if (!_wait_for_level(1)) return false;
+    uint32_t duration = time_us_32() - start;
+    data[i / 8] <<= 1;
+    if (duration > 40) data[i / 8] |= 1;
+    return true;
+}
+
+
+/**
+ * @brief Read all 40 data bits from the DHT11
+ *
+ * @param data 5-byte array filled with the received data
+ * @return bool true if all 40 bits were read, false on timeout
+ */
+static bool _read_40_bits(uint8_t *data) {
+    for (int i = 0; i < 40; i++)
+        if (!_read_bit(data, i)) return false;
+    return true;
+}
+
+
+/**
+ * @brief Verify the DHT11 checksum byte
+ *
+ * @param data 5-byte received data (bytes 0-3 plus checksum in byte 4)
+ * @return bool true if the checksum matches, false otherwise
+ */
+static bool _validate_checksum(const uint8_t *data) {
+    return data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF);
+}
+
+
+void dht11_init(uint8_t pin) {
+    dht_pin = pin;
+    gpio_init(pin);
+    gpio_pull_up(pin);
+}
+
+
+bool dht11_read(float *humidity, float *temperature) {
+    uint8_t data[5] = {0};
+    _send_start_signal();
+    if (!_wait_response()) return false;
+    if (!_read_40_bits(data)) return false;
+    if (!_validate_checksum(data)) return false;
     *humidity = data[0] + data[1] * 0.1f;
     *temperature = data[2] + data[3] * 0.1f;
     return true;