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

firmware/src/board/heltec_v4.rs

@@ -1,11 +1,9 @@
 use esp_hal::gpio::{Level, Output, OutputConfig};
-use esp_hal::rmt::{Rmt, TxChannelConfig, TxChannelCreator};
-use esp_hal::time::Rate;
 use static_cell::StaticCell;
 
 use super::esp32s3;
 use super::traits::{BoardParts, LoRaBoard};
-use crate::driver::ws2812::Ws2812;
+use crate::driver::simple_led::SimpleLed;
 use crate::hal::esp32s3 as mcu;
 
 pub use super::esp32s3::{
@@ -14,7 +12,7 @@ pub use super::esp32s3::{
 
 pub type UsbDriver = esp_hal::otg_fs::asynch::Driver<'static>;
 
-pub type LedDriver = Ws2812;
+pub type LedDriver = SimpleLed;
 
 pub struct UsbParts {
     pub driver: UsbDriver,
@@ -32,7 +30,7 @@ impl LoRaBoard for Board {
     type CommParts = UsbParts;
     type DisplayParts = DisplayParts;
     type DisplayDriver = DisplayDriver;
-    type LedDriver = Ws2812;
+    type LedDriver = LedDriver;
 
     fn init() -> Self {
         let p = esp_hal::init(esp_hal::Config::default());
@@ -43,7 +41,7 @@ impl LoRaBoard for Board {
         mcu::mac_address()
     }
 
-    fn into_parts(self) -> BoardParts<RadioParts, UsbParts, DisplayParts, Ws2812> {
+    fn into_parts(self) -> BoardParts<RadioParts, UsbParts, DisplayParts, LedDriver> {
         let p = self.p;
 
         mcu::start_timer(p.TIMG0);
@@ -77,18 +75,9 @@ impl LoRaBoard for Board {
         let i2c = mcu::init_i2c(p.I2C0, p.GPIO17, p.GPIO18);
         let display = Some(DisplayParts { i2c });
 
-        // WS2812B RGB LED on GPIO38 via RMT channel 0 (blocking, ~31µs per update)
-        let rmt = Rmt::new(p.RMT, Rate::from_mhz(80)).expect("RMT init");
-        let led_channel = rmt
-            .channel0
-            .configure_tx(
-                p.GPIO38,
-                TxChannelConfig::default()
-                    .with_clk_divider(1)
-                    .with_idle_output(true),
-            )
-            .expect("RMT TX channel init");
-        let led = Some(Ws2812::new(led_channel));
+        // Orange LED on GPIO35
+        let led_pin = Output::new(p.GPIO35, Level::Low, OutputConfig::default());
+        let led = Some(SimpleLed::new(led_pin));
 
         BoardParts {
             radio,

firmware/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;

firmware/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
-                }
-            }
-        }
-    }
-}