feat: add waiting state; start communication

Author: zeldan

README.md

@@ -1,5 +1,6 @@
 # embedded-dht-rs
 
+![steps](/docs/steps.png)
 
 ## Step 1
 

docs/steps.png

@@ -1,18 +1,56 @@
 #![no_std]
 
-use embedded_hal::digital::{ErrorType, InputPin, OutputPin};
+use embedded_hal::{
+    delay::DelayNs,
+    digital::{ErrorType, InputPin, OutputPin, PinState},
+};
 
-pub struct Dht11<P: InputPin + OutputPin> {
-    pin: P
+pub struct Dht11<P: InputPin + OutputPin, D: DelayNs> {
+    pin: P,
+    delay: D,
 }
 
-impl<P: InputPin + OutputPin> Dht11<P> {
-
-    pub fn new(pin: P) -> Self {
-       Self { pin } 
+impl<P: InputPin + OutputPin, D: DelayNs> Dht11<P, D> {
+    pub fn new(pin: P, delay: D) -> Self {
+        Self { pin, delay }
     }
 
     pub fn read(&mut self) -> Result<bool, <P as ErrorType>::Error> {
+        // Start communication: pull pin low for 18ms, then release.
+        let _ = self.pin.set_low();
+        self.delay.delay_ms(18); 
+        let _ = self.pin.set_high();
+
+        // Wait for sensor to respond.
+        self.delay.delay_us(48);
+
+        // Sync with sensor: wait for high then low signals.
+        let _ = self.wait_until_state(PinState::High);
+        let _ = self.wait_until_state(PinState::Low);
+
+        // Start reading 
+
+        // TODO
+
         return self.pin.is_high();
     }
-}
+
+    /// Waits until the pin reaches the specified state.
+    ///
+    /// This helper function continuously polls the pin until it reaches the desired `PinState`.
+    ///
+    /// # Arguments
+    ///
+    /// * `state` - The target `PinState` to wait for (either `Low` or `High`).
+    fn wait_until_state(&mut self, state: PinState) -> Result<(), <P as ErrorType>::Error>{
+        loop {
+            match state {
+                PinState::Low => if self.pin.is_low()? { break; },
+                PinState::High => if self.pin.is_high()? { break; }
+            };
+            self.delay.delay_us(1);
+        }
+        Ok(())
+    }
+}
+