feat: add Heltec V4, wire up V3/V4 peripherals, restructure entry point

- Add heltec_v4 board: ESP32-S3R2, SX1262, SSD1315 display, native USB,
  Vext on GPIO36 (active HIGH)
- Wire up heltec_v3 with real esp-hal peripherals (was a stub)
- V3 and V4 share radio/I2C pins, differ in Vext pin/polarity and
  display reset
- Restructure main.rs: cfg_if selects embassy_executor::main (Cortex-M)
  vs esp_hal_embassy::main (Xtensa) per board
- Display detection via SSD1306 init in display_task — boards always
  provide I2C bus, task exits gracefully if no display responds

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -48,6 +48,12 @@ heltec_v3 = [
     "dep:esp-hal-embassy",
     "dep:esp-println",
 ]
+heltec_v4 = [
+    "dep:esp-backtrace",
+    "dep:esp-hal",
+    "dep:esp-hal-embassy",
+    "dep:esp-println",
+]
 rak_4631 = [
     "dep:cortex-m-rt",
     "dep:embassy-nrf",

Justfile

@@ -4,12 +4,13 @@ set shell := ["bash", "-c"]
 # Xtensa targets use nightly cargo + esp rustc + -Zbuild-std=core.
 # check-all gracefully skips boards whose toolchain isn't installed.
 heltec_v3 := "heltec_v3 xtensa-esp32s3-none-elf esp32s3"
+heltec_v4 := "heltec_v4 xtensa-esp32s3-none-elf esp32s3"
 rak_4631  := "rak_4631 thumbv7em-none-eabihf nRF52840_xxAA"
 
 firmware_dir := "firmware"
 
 # All known boards
-boards := "heltec_v3 rak_4631"
+boards := "heltec_v3 heltec_v4 rak_4631"
 
 # Check all boards that can build with the available toolchain
 check-all:
@@ -79,5 +80,6 @@ _copy_firmware board profile:
 [private]
 _info name:
     @if [ "{{name}}" == "heltec_v3" ]; then echo "{{heltec_v3}}"; \
+     elif [ "{{name}}" == "heltec_v4" ]; then echo "{{heltec_v4}}"; \
      elif [ "{{name}}" == "rak_4631" ]; then echo "{{rak_4631}}"; \
      else echo "Unknown board: {{name}}" >&2; exit 1; fi

src/board/heltec_v3.rs

@@ -1,21 +1,30 @@
+use embassy_embedded_hal::shared_bus::asynch::spi::SpiDevice;
+use embassy_sync::blocking_mutex::raw::NoopRawMutex;
 use embassy_time::Delay;
+use esp_hal::dma::{Dma, DmaPriority};
+use esp_hal::gpio::{Input, Level, Output, Pull};
+use esp_hal::i2c::master::{Config as I2cConfig, I2c};
+use esp_hal::prelude::*;
+use esp_hal::spi::master::{Config as SpiConfig, Spi, SpiDmaBus};
+use esp_hal::spi::SpiMode;
+use esp_hal::timer::timg::TimerGroup;
+use static_cell::StaticCell;
 
 use lora_phy::iv::GenericSx126xInterfaceVariant;
-use lora_phy::sx126x::{Sx1262, Sx126x};
+use lora_phy::sx126x::{self, Sx1262, Sx126x};
 
 // ── Concrete peripheral types ────────────────────────────────────────
 
-// TODO: replace these placeholders with real esp-hal peripheral types
-//   SPI2 for SX1262 (SCK=9, MOSI=10, MISO=11, NSS=8)
-//   GPIO for radio control (RST=12, DIO1=14, BUSY=13)
-//   Vext pin (GPIO21) LOW to power OLED
-//   I2C0 for SSD1306 (SDA=17, SCL=18)
-//   USB OTG for CDC-ACM
-
-type Iv = GenericSx126xInterfaceVariant<(), ()>;
-type RadioSpiDevice = ();
+type SpiBus = SpiDmaBus<'static, esp_hal::Async>;
+type Nss = Output<'static>;
+type Iv = GenericSx126xInterfaceVariant<Output<'static>, Input<'static>>;
+type RadioSpiDevice = SpiDevice<'static, NoopRawMutex, SpiBus, Nss>;
 pub type RadioDriver = Sx126x<RadioSpiDevice, Iv, Sx1262>;
 
+pub type UsbDriver = esp_hal::otg_fs::asynch::Driver<'static>;
+
+pub type DisplayI2c = I2c<'static, esp_hal::Async>;
+
 // ── Peripheral bundles ───────────────────────────────────────────────
 
 pub struct RadioParts {
@@ -24,25 +33,105 @@ pub struct RadioParts {
 }
 
 pub struct UsbParts {
-    pub driver: (),
+    pub driver: UsbDriver,
 }
 
 pub struct DisplayParts {
-    pub i2c: (),
+    pub i2c: DisplayI2c,
 }
 
 // ── Board init ───────────────────────────────────────────────────────
 
-pub struct Board;
+pub struct Board {
+    p: esp_hal::peripherals::Peripherals,
+}
 
 impl Board {
     pub fn init() -> Self {
-        // TODO: call esp_hal::init(esp_hal::Config::default())
-        Self
+        let mut p = esp_hal::init(esp_hal::Config::default());
+
+        let timg0 = TimerGroup::new(core::mem::replace(
+            &mut p.TIMG0,
+            unsafe { esp_hal::peripherals::TIMG0::steal() },
+        ));
+        esp_hal_embassy::init(timg0.timer0);
+
+        Self { p }
     }
 
     pub fn into_parts(self) -> (RadioParts, UsbParts, Option<DisplayParts>) {
-        // TODO: wire up real peripherals once building with nightly + -Zbuild-std
-        todo!("Heltec V3 peripheral init")
+        let p = self.p;
+
+        // ── Vext power: GPIO21, active LOW to enable OLED ──────────
+        let _vext = Output::new(p.GPIO21, Level::Low);
+
+        // ── DMA for SPI ────────────────────────────────────────────
+        let dma = Dma::new(p.DMA);
+        let dma_ch = dma.channel0.configure(false, DmaPriority::Priority0);
+
+        // ── SPI + DMA for SX1262 ───────────────────────────────────
+        let spi = Spi::new_with_config(p.SPI2, SpiConfig {
+            frequency: 1u32.MHz(),
+            mode: SpiMode::Mode0,
+            ..Default::default()
+        })
+        .with_sck(p.GPIO9)
+        .with_mosi(p.GPIO10)
+        .with_miso(p.GPIO11)
+        .with_dma(dma_ch);
+
+        let (rx_buf, rx_desc, tx_buf, tx_desc) = esp_hal::dma_buffers!(256);
+        let dma_rx = esp_hal::dma::DmaRxBuf::new(rx_desc, rx_buf).unwrap();
+        let dma_tx = esp_hal::dma::DmaTxBuf::new(tx_desc, tx_buf).unwrap();
+
+        let spi = spi.with_buffers(dma_rx, dma_tx).into_async();
+
+        static SPI_BUS: StaticCell<embassy_sync::mutex::Mutex<NoopRawMutex, SpiBus>> =
+            StaticCell::new();
+        let spi_bus = SPI_BUS.init(embassy_sync::mutex::Mutex::new(spi));
+
+        let nss = Output::new(p.GPIO8, Level::High);
+        let spi_device = SpiDevice::new(spi_bus, nss);
+
+        // ── SX1262 control pins ────────────────────────────────────
+        let reset = Output::new(p.GPIO12, Level::High);
+        let dio1 = Input::new(p.GPIO14, Pull::Down);
+        let busy = Input::new(p.GPIO13, Pull::Down);
+
+        let iv = GenericSx126xInterfaceVariant::new(reset, dio1, busy, None, None).unwrap();
+
+        let sx_config = sx126x::Config {
+            chip: Sx1262,
+            tcxo_ctrl: Some(sx126x::TcxoCtrlVoltage::Ctrl1V7),
+            use_dcdc: true,
+            rx_boost: false,
+        };
+
+        let radio = RadioParts {
+            driver: Sx126x::new(spi_device, iv, sx_config),
+            delay: Delay,
+        };
+
+        // ── USB (native ESP32-S3 OTG) ─────────────────────────────
+        let usb_inst = esp_hal::otg_fs::Usb::new(p.USB0, p.GPIO20, p.GPIO19);
+        static EP_OUT_BUF: StaticCell<[u8; 1024]> = StaticCell::new();
+        let ep_out_buf = EP_OUT_BUF.init([0u8; 1024]);
+        let usb = UsbParts {
+            driver: esp_hal::otg_fs::asynch::Driver::new(
+                usb_inst,
+                ep_out_buf,
+                esp_hal::otg_fs::asynch::Config::default(),
+            ),
+        };
+
+        // ── Display (optional SSD1306 OLED on I2C, 0x3C) ──────────
+        // Always provide I2C; display_task detects presence via SSD1306 init.
+        let i2c = I2c::new(p.I2C0, I2cConfig::default())
+            .with_sda(p.GPIO17)
+            .with_scl(p.GPIO18)
+            .into_async();
+        let display = Some(DisplayParts { i2c });
+
+        (radio, usb, display)
     }
 }

src/board/heltec_v4.rs

@@ -0,0 +1,142 @@
+use embassy_embedded_hal::shared_bus::asynch::spi::SpiDevice;
+use embassy_sync::blocking_mutex::raw::NoopRawMutex;
+use embassy_time::Delay;
+use esp_hal::dma::{Dma, DmaPriority};
+use esp_hal::gpio::{Input, Level, Output, Pull};
+use esp_hal::i2c::master::{Config as I2cConfig, I2c};
+use esp_hal::prelude::*;
+use esp_hal::spi::master::{Config as SpiConfig, Spi, SpiDmaBus};
+use esp_hal::spi::SpiMode;
+use esp_hal::timer::timg::TimerGroup;
+use static_cell::StaticCell;
+
+use lora_phy::iv::GenericSx126xInterfaceVariant;
+use lora_phy::sx126x::{self, Sx1262, Sx126x};
+
+// ── Concrete peripheral types ────────────────────────────────────────
+
+type SpiBus = SpiDmaBus<'static, esp_hal::Async>;
+type Nss = Output<'static>;
+type Iv = GenericSx126xInterfaceVariant<Output<'static>, Input<'static>>;
+type RadioSpiDevice = SpiDevice<'static, NoopRawMutex, SpiBus, Nss>;
+pub type RadioDriver = Sx126x<RadioSpiDevice, Iv, Sx1262>;
+
+pub type UsbDriver = esp_hal::otg_fs::asynch::Driver<'static>;
+
+pub type DisplayI2c = I2c<'static, esp_hal::Async>;
+
+// ── Peripheral bundles ───────────────────────────────────────────────
+
+pub struct RadioParts {
+    pub driver: RadioDriver,
+    pub delay: Delay,
+}
+
+pub struct UsbParts {
+    pub driver: UsbDriver,
+}
+
+pub struct DisplayParts {
+    pub i2c: DisplayI2c,
+}
+
+// ── Board init ───────────────────────────────────────────────────────
+
+pub struct Board {
+    p: esp_hal::peripherals::Peripherals,
+}
+
+impl Board {
+    pub fn init() -> Self {
+        let mut p = esp_hal::init(esp_hal::Config::default());
+
+        // Init embassy time driver before consuming peripherals
+        let timg0 = TimerGroup::new(core::mem::replace(
+            &mut p.TIMG0,
+            unsafe { esp_hal::peripherals::TIMG0::steal() },
+        ));
+        esp_hal_embassy::init(timg0.timer0);
+
+        Self { p }
+    }
+
+    pub fn into_parts(self) -> (RadioParts, UsbParts, Option<DisplayParts>) {
+        let p = self.p;
+
+        // ── Vext power: GPIO36, active HIGH to enable OLED ─────────
+        let _vext = Output::new(p.GPIO36, Level::High);
+
+        // ── DMA for SPI ────────────────────────────────────────────
+        let dma = Dma::new(p.DMA);
+        let dma_ch = dma.channel0.configure(false, DmaPriority::Priority0);
+
+        // ── SPI + DMA for SX1262 ───────────────────────────────────
+        let spi = Spi::new_with_config(p.SPI2, SpiConfig {
+            frequency: 1u32.MHz(),
+            mode: SpiMode::Mode0,
+            ..Default::default()
+        })
+        .with_sck(p.GPIO9)
+        .with_mosi(p.GPIO10)
+        .with_miso(p.GPIO11)
+        .with_dma(dma_ch);
+
+        let (rx_buf, rx_desc, tx_buf, tx_desc) = esp_hal::dma_buffers!(256);
+        let dma_rx = esp_hal::dma::DmaRxBuf::new(rx_desc, rx_buf).unwrap();
+        let dma_tx = esp_hal::dma::DmaTxBuf::new(tx_desc, tx_buf).unwrap();
+
+        let spi = spi.with_buffers(dma_rx, dma_tx).into_async();
+
+        static SPI_BUS: StaticCell<embassy_sync::mutex::Mutex<NoopRawMutex, SpiBus>> =
+            StaticCell::new();
+        let spi_bus = SPI_BUS.init(embassy_sync::mutex::Mutex::new(spi));
+
+        let nss = Output::new(p.GPIO8, Level::High);
+        let spi_device = SpiDevice::new(spi_bus, nss);
+
+        // ── SX1262 control pins ────────────────────────────────────
+        let reset = Output::new(p.GPIO12, Level::High);
+        let dio1 = Input::new(p.GPIO14, Pull::Down);
+        let busy = Input::new(p.GPIO13, Pull::Down);
+
+        let iv = GenericSx126xInterfaceVariant::new(reset, dio1, busy, None, None).unwrap();
+
+        let sx_config = sx126x::Config {
+            chip: Sx1262,
+            tcxo_ctrl: Some(sx126x::TcxoCtrlVoltage::Ctrl1V7),
+            use_dcdc: true,
+            rx_boost: false,
+        };
+
+        let radio = RadioParts {
+            driver: Sx126x::new(spi_device, iv, sx_config),
+            delay: Delay,
+        };
+
+        // ── USB (native ESP32-S3 OTG) ─────────────────────────────
+        let usb_inst = esp_hal::otg_fs::Usb::new(p.USB0, p.GPIO20, p.GPIO19);
+        static EP_OUT_BUF: StaticCell<[u8; 1024]> = StaticCell::new();
+        let ep_out_buf = EP_OUT_BUF.init([0u8; 1024]);
+        let usb = UsbParts {
+            driver: esp_hal::otg_fs::asynch::Driver::new(
+                usb_inst,
+                ep_out_buf,
+                esp_hal::otg_fs::asynch::Config::default(),
+            ),
+        };
+
+        // ── Display (optional SSD1315 OLED on I2C, 0x3C) ──────────
+        // Reset display controller via GPIO21
+        let mut display_rst = Output::new(p.GPIO21, Level::Low);
+        display_rst.set_high();
+
+        // Always provide I2C; display_task detects presence via SSD1306 init.
+        let i2c = I2c::new(p.I2C0, I2cConfig::default())
+            .with_sda(p.GPIO17)
+            .with_scl(p.GPIO18)
+            .into_async();
+        let display = Some(DisplayParts { i2c });
+
+        (radio, usb, display)
+    }
+}

src/board/rak_4631.rs

@@ -103,7 +103,8 @@ impl Board {
         };
 
         // ── Display (optional RAK1921 SSD1306 OLED on I2C) ──────
-        // TODO: probe I2C address 0x3C to detect presence
+        // Always provide the I2C bus; display_task detects presence
+        // via SSD1306 init (fails gracefully if no display attached).
         let i2c_cfg = twim::Config::default();
         let i2c = Twim::new(p.TWISPI0, Irqs, p.P0_13, p.P0_14, i2c_cfg);
         let display = Some(DisplayParts { i2c });

src/main.rs

@@ -15,7 +15,7 @@ use crate::channel::{CommandChannel, DisplayCommandChannel, ResponseChannel, Sta
 cfg_if::cfg_if! {
     if #[cfg(feature = "rak_4631")] {
         use panic_probe as _;
-    } else if #[cfg(feature = "heltec_v3")] {
+    } else if #[cfg(any(feature = "heltec_v3", feature = "heltec_v4"))] {
         use esp_backtrace as _;
     }
 }
@@ -25,8 +25,22 @@ static RESPONSES: ResponseChannel = ResponseChannel::new();
 static STATUS: StatusWatch = StatusWatch::new();
 static DISPLAY_COMMANDS: DisplayCommandChannel = DisplayCommandChannel::new();
 
+// Entry point: each platform needs its own executor macro.
+cfg_if::cfg_if! {
+    if #[cfg(feature = "rak_4631")] {
         #[embassy_executor::main]
         async fn main(spawner: Spawner) {
+            run(spawner).await;
+        }
+    } else if #[cfg(any(feature = "heltec_v3", feature = "heltec_v4"))] {
+        #[esp_hal_embassy::main]
+        async fn main(spawner: Spawner) {
+            run(spawner).await;
+        }
+    }
+}
+
+async fn run(spawner: Spawner) {
     let board = board::Board::init();
     let (radio, usb, display) = board.into_parts();