style: enforce coding standard — headers, @brief on #define, Doxygen on statics, remove _ prefix, max 8 lines per function

0x001a_operators/dht11.c

@@ -31,8 +31,97 @@
 #include "hardware/gpio.h"
 #include "pico/time.h"
 
+/** @brief GPIO pin connected to the DHT11 sensor */
 static uint dht_pin;
 
+/**
+ * @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);
+}
+
+/**
+ * @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) == 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);
@@ -41,38 +130,10 @@ void dht11_init(uint8_t pin) {
 
 bool dht11_read(float *humidity, float *temperature) {
     uint8_t data[5] = {0};
-    
-    // Start signal
-    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
-    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;
-    
+    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;