fix: V4 also has plain LED on GPIO35, not WS2812 on GPIO38

Per the official V4 schematic (HTIT-WB32LAF_V4.3.pdf), the V4 has
an orange LED on GPIO35 with a series resistor — same setup as V3.
GPIO38 is GNSS_RX on V4, not an LED. Neither V3 nor V4 has a WS2812.

- V4: switched from WS2812/GPIO38 to SimpleLed/GPIO35
- Removed ws2812.rs driver (no current board uses addressable LEDs)
- All ESP boards now use the same SimpleLed driver on GPIO35

src/driver/mod.rs

@@ -1,8 +1,5 @@
 #[cfg(feature = "wio_tracker_l1")]
 pub mod sh1106;
 
-#[cfg(any(feature = "heltec_v3", feature = "heltec_v3_uart"))]
+#[cfg(any(feature = "heltec_v3", feature = "heltec_v3_uart", feature = "heltec_v4"))]
 pub mod simple_led;
-
-#[cfg(feature = "heltec_v4")]
-pub mod ws2812;

src/driver/ws2812.rs

@@ -1,64 +0,0 @@
-//! WS2812B single-LED driver using the ESP32-S3 RMT peripheral.
-//!
-//! Encodes RGB values as GRB PulseCodes and transmits via RMT.
-//! At 80 MHz with divider=1, each tick is 12.5 ns.
-//! Uses blocking transmit (~31µs per LED update).
-
-use esp_hal::gpio::Level;
-use esp_hal::rmt::{Channel, PulseCode, Tx};
-
-use crate::board::RgbLed;
-
-/// WS2812 0-bit: High 400ns (32 ticks), Low 850ns (68 ticks).
-const BIT_0: PulseCode = PulseCode::new(Level::High, 32, Level::Low, 68);
-
-/// WS2812 1-bit: High 800ns (64 ticks), Low 450ns (36 ticks).
-const BIT_1: PulseCode = PulseCode::new(Level::High, 64, Level::Low, 36);
-
-/// WS2812B single-LED driver over RMT (blocking).
-pub struct Ws2812 {
-    channel: Option<Channel<'static, esp_hal::Blocking, Tx>>,
-}
-
-impl Ws2812 {
-    pub fn new(channel: Channel<'static, esp_hal::Blocking, Tx>) -> Self {
-        Self {
-            channel: Some(channel),
-        }
-    }
-
-    /// Encode 3 bytes (GRB order) + end marker into PulseCodes.
-    fn encode(r: u8, g: u8, b: u8) -> [PulseCode; 25] {
-        let mut data = [PulseCode::end_marker(); 25];
-        let bytes = [g, r, b]; // WS2812 expects GRB order
-        let mut idx = 0;
-        for byte in bytes {
-            for bit in (0..8).rev() {
-                data[idx] = if byte & (1 << bit) != 0 { BIT_1 } else { BIT_0 };
-                idx += 1;
-            }
-        }
-        data
-    }
-}
-
-impl RgbLed for Ws2812 {
-    async fn set_rgb(&mut self, r: u8, g: u8, b: u8) {
-        let data = Self::encode(r, g, b);
-        if let Some(ch) = self.channel.take() {
-            match ch.transmit(&data) {
-                Ok(tx) => match tx.wait() {
-                    Ok(ch) => self.channel = Some(ch),
-                    Err((e, ch)) => {
-                        defmt::warn!("WS2812 wait error: {}", e);
-                        self.channel = Some(ch);
-                    }
-                },
-                Err(e) => {
-                    defmt::warn!("WS2812 transmit error: {}", e);
-                    // Channel consumed on transmit error — LED is lost
-                }
-            }
-        }
-    }
-}