fix: V3 has white LED on GPIO35, not WS2812B on GPIO38

The Heltec V3 has a plain white LED on GPIO35 (simple GPIO, not
addressable). Only the V4 has a WS2812B RGB LED on GPIO38.

- Created driver/simple_led.rs for single-color GPIO LEDs
- V3/V3-UART boards: SimpleLed on GPIO35 (white blink on RX/TX)
- V4 board: unchanged (WS2812 on GPIO38, green/red colors)
- nRF boards: unchanged (no LED, type LedDriver = ())

firmware/src/board/heltec_v3.rs

@@ -7,13 +7,11 @@
 //! For stock (unmodified) V3 boards, use the `heltec_v3_uart` feature instead.
 
 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::{
@@ -21,7 +19,7 @@ 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,
@@ -39,7 +37,7 @@ 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());
@@ -50,7 +48,7 @@ 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);
@@ -84,14 +82,9 @@ 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
+        // White LED on GPIO35
-        let rmt = Rmt::new(p.RMT, Rate::from_mhz(80))
+        let led_pin = Output::new(p.GPIO35, Level::Low, OutputConfig::default());
-            .expect("RMT init")
+        let led = Some(SimpleLed::new(led_pin));
-            .into_async();
-        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));
 
         BoardParts {
             radio,

firmware/src/board/heltec_v3_uart.rs

@@ -7,12 +7,10 @@
 //! use the `heltec_v3` feature instead for native USB CDC-ACM support.
 
 use esp_hal::gpio::{Level, Output, OutputConfig};
-use esp_hal::rmt::{Rmt, TxChannelConfig, TxChannelCreator};
-use esp_hal::time::Rate;
 
 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::{
@@ -20,7 +18,7 @@ pub use super::esp32s3::{
 };
 
 pub type UartDriver = esp_hal::uart::Uart<'static, esp_hal::Async>;
-pub type LedDriver = Ws2812;
+pub type LedDriver = SimpleLed;
 
 pub struct UartParts {
     pub driver: UartDriver,
@@ -38,7 +36,7 @@ impl LoRaBoard for Board {
     type CommParts = UartParts;
     type DisplayParts = DisplayParts;
     type DisplayDriver = DisplayDriver;
-    type LedDriver = Ws2812;
+    type LedDriver = LedDriver;
 
     fn init() -> Self {
         let p = esp_hal::init(esp_hal::Config::default());
@@ -49,7 +47,7 @@ impl LoRaBoard for Board {
         mcu::mac_address()
     }
 
-    fn into_parts(self) -> BoardParts<RadioParts, UartParts, DisplayParts, Ws2812> {
+    fn into_parts(self) -> BoardParts<RadioParts, UartParts, DisplayParts, LedDriver> {
         let p = self.p;
 
         mcu::start_timer(p.TIMG0);
@@ -80,14 +78,9 @@ 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
+        // White LED on GPIO35
-        let rmt = Rmt::new(p.RMT, Rate::from_mhz(80))
+        let led_pin = Output::new(p.GPIO35, Level::Low, OutputConfig::default());
-            .expect("RMT init")
+        let led = Some(SimpleLed::new(led_pin));
-            .into_async();
-        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));
 
         BoardParts {
             radio,

firmware/src/driver/mod.rs

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

firmware/src/driver/simple_led.rs

@@ -0,0 +1,28 @@
+//! Simple single-color LED driver (GPIO on/off).
+//!
+//! For boards with a plain LED (not addressable RGB). Any non-zero
+//! RGB value turns the LED on; all zeros turns it off.
+
+use esp_hal::gpio::Output;
+
+use crate::board::RgbLed;
+
+pub struct SimpleLed {
+    pin: Output<'static>,
+}
+
+impl SimpleLed {
+    pub fn new(pin: Output<'static>) -> Self {
+        Self { pin }
+    }
+}
+
+impl RgbLed for SimpleLed {
+    async fn set_rgb(&mut self, r: u8, g: u8, b: u8) {
+        if r > 0 || g > 0 || b > 0 {
+            self.pin.set_high();
+        } else {
+            self.pin.set_low();
+        }
+    }
+}