feat: Heltec V3 native USB, remove all dead_code suppressions

- heltec_v3 now uses USB OTG (requires hardware mod: solder R29/R3)
- heltec_v3_uart added as fallback for stock boards
- Removed every #[allow(dead_code)] — fixed root causes instead:
  - Comm types (UsbParts/UartParts) moved to individual board files
  - USB/UART init removed from hal (boards call esp-hal directly)
  - SH1106 driver gated on boards that use it
  - UART task sends DisplayCommand::Reset at startup (variant now used)
  - ErrorCode::CrcError removed (SX1262 drops bad-CRC silently)
- check/clippy now use --release (no more Xtensa dev-mode warnings)
- Updated README with hardware mod docs and board table

justfile

@@ -57,11 +57,11 @@ check-all:
 
 # Check a single board compiles
 check board:
-    @just _cargo {{board}} check
+    @just _cargo {{board}} "check --release"
 
 # Run clippy on a single board
 clippy board:
-    @just _cargo {{board}} "clippy" "-- -D warnings"
+    @just _cargo {{board}} "clippy --release" "-- -D warnings"
 
 # Build release firmware and copy to builds/ with a readable name
 build board profile="release":

src/board/esp32s3.rs

@@ -1,7 +1,8 @@
 //! Shared types and peripheral wiring for ESP32-S3 boards.
 //!
 //! Delegates MCU-level init to `hal::esp32s3` and defines peripheral-level
-//! types (RadioDriver, Parts structs) used by ESP32-S3 board files.
+//! types (RadioDriver, display) used by ESP32-S3 board files.
+//! Each board defines its own comm types (UsbParts/UartParts) directly.
 
 use embassy_embedded_hal::shared_bus::asynch::spi::SpiDevice;
 use embassy_sync::blocking_mutex::raw::NoopRawMutex;
@@ -15,8 +16,7 @@ use crate::hal::esp32s3 as mcu;
 
 // ── Re-export MCU types ─────────────────────────────────────────────
 
-#[allow(unused_imports)] // Each board uses one of USB/UART, not both
-pub use mcu::{I2cBus as DisplayI2c, SpiBus, UartDriver, UsbOtgDriver as UsbDriver};
+pub use mcu::{I2cBus as DisplayI2c, SpiBus};
 
 // ── Concrete peripheral types ───────────────────────────────────────
 
@@ -32,16 +32,6 @@ pub struct RadioParts {
     pub delay: Delay,
 }
 
-#[allow(dead_code)] // Not used by heltec_v3_uart
-pub struct UsbParts {
-    pub driver: UsbDriver,
-}
-
-#[allow(dead_code)] // Only used by heltec_v3_uart
-pub struct UartParts {
-    pub driver: UartDriver,
-}
-
 pub struct DisplayParts {
     pub i2c: DisplayI2c,
 }

src/board/heltec_v3.rs

@@ -7,17 +7,22 @@
 //! For stock (unmodified) V3 boards, use the `heltec_v3_uart` feature instead.
 
 use esp_hal::gpio::{Level, Output, OutputConfig};
+use static_cell::StaticCell;
 
 use super::esp32s3;
 use super::traits::{BoardParts, LoRaBoard};
 use crate::hal::esp32s3 as mcu;
 
-#[allow(unused_imports)] // Re-exported for other modules (display, radio, host tasks)
 pub use super::esp32s3::{
-    create_display, DisplayDriver, DisplayI2c, DisplayParts, RadioDriver, RadioParts, UsbDriver,
-    UsbParts,
+    create_display, DisplayDriver, DisplayParts, RadioDriver, RadioParts,
 };
 
+pub type UsbDriver = esp_hal::otg_fs::asynch::Driver<'static>;
+
+pub struct UsbParts {
+    pub driver: UsbDriver,
+}
+
 pub struct Board {
     p: esp_hal::peripherals::Peripherals,
 }
@@ -53,9 +58,15 @@ impl LoRaBoard for Board {
         let radio = esp32s3::init_radio(spi_bus, p.GPIO8, p.GPIO12, p.GPIO14, p.GPIO13);
 
         // Note: switches internal USB PHY from Serial-JTAG to OTG.
-        // espflash --monitor will stop working after this point.
+        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 host = UsbParts {
-            driver: mcu::init_usb(p.USB0, p.GPIO20, p.GPIO19),
+            driver: esp_hal::otg_fs::asynch::Driver::new(
+                usb_inst,
+                ep_out_buf,
+                esp_hal::otg_fs::asynch::Config::default(),
+            ),
         };
 
         // SSD1306 display reset: pulse GPIO21 low->high before I2C init

src/board/heltec_v3_uart.rs

@@ -12,12 +12,16 @@ use super::esp32s3;
 use super::traits::{BoardParts, LoRaBoard};
 use crate::hal::esp32s3 as mcu;
 
-#[allow(unused_imports)] // Re-exported for other modules (display, radio, host tasks)
 pub use super::esp32s3::{
-    create_display, DisplayDriver, DisplayI2c, DisplayParts, RadioDriver, RadioParts, UartDriver,
-    UartParts,
+    create_display, DisplayDriver, DisplayParts, RadioDriver, RadioParts,
 };
 
+pub type UartDriver = esp_hal::uart::Uart<'static, esp_hal::Async>;
+
+pub struct UartParts {
+    pub driver: UartDriver,
+}
+
 pub struct Board {
     p: esp_hal::peripherals::Peripherals,
 }
@@ -51,8 +55,14 @@ impl LoRaBoard for Board {
 
         let spi_bus = mcu::init_spi(p.SPI2, p.DMA_CH0, p.GPIO9, p.GPIO10, p.GPIO11);
         let radio = esp32s3::init_radio(spi_bus, p.GPIO8, p.GPIO12, p.GPIO14, p.GPIO13);
+
+        use esp_hal::uart::{Config as UartConfig, Uart};
         let host = UartParts {
-            driver: mcu::init_uart(p.UART0, p.GPIO43, p.GPIO44),
+            driver: Uart::new(p.UART0, UartConfig::default())
+                .expect("UART init")
+                .with_tx(p.GPIO43)
+                .with_rx(p.GPIO44)
+                .into_async(),
         };
 
         // SSD1306 display reset: pulse GPIO21 low->high before I2C init

src/board/heltec_v4.rs

@@ -1,15 +1,20 @@
 use esp_hal::gpio::{Level, Output, OutputConfig};
+use static_cell::StaticCell;
 
 use super::esp32s3;
 use super::traits::{BoardParts, LoRaBoard};
 use crate::hal::esp32s3 as mcu;
 
-#[allow(unused_imports)] // Re-exported for other modules (display, radio, host tasks)
 pub use super::esp32s3::{
-    create_display, DisplayDriver, DisplayI2c, DisplayParts, RadioDriver, RadioParts, UsbDriver,
-    UsbParts,
+    create_display, DisplayDriver, DisplayParts, RadioDriver, RadioParts,
 };
 
+pub type UsbDriver = esp_hal::otg_fs::asynch::Driver<'static>;
+
+pub struct UsbParts {
+    pub driver: UsbDriver,
+}
+
 pub struct Board {
     p: esp_hal::peripherals::Peripherals,
 }
@@ -45,8 +50,15 @@ impl LoRaBoard for Board {
         let radio = esp32s3::init_radio(spi_bus, p.GPIO8, p.GPIO12, p.GPIO14, p.GPIO13);
 
         // Note: switches internal USB PHY from Serial-JTAG to 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 host = UsbParts {
-            driver: mcu::init_usb(p.USB0, p.GPIO20, p.GPIO19),
+            driver: esp_hal::otg_fs::asynch::Driver::new(
+                usb_inst,
+                ep_out_buf,
+                esp_hal::otg_fs::asynch::Config::default(),
+            ),
         };
 
         // SSD1315 display reset: pulse GPIO21 low->high before I2C init

src/channel.rs

@@ -14,7 +14,6 @@ use crate::protocol::{Command, RadioConfig, Response};
 
 /// Display commands routed from host_task to display_task.
 #[derive(Debug, Clone, Copy, defmt::Format)]
-#[allow(dead_code)] // Reset is only used by USB boards (DTR disconnect detection)
 pub enum DisplayCommand {
     On,
     Off,

src/driver/mod.rs

@@ -1,2 +1,2 @@
-#[allow(dead_code)]
+#[cfg(feature = "wio_tracker_l1")]
 pub mod sh1106;

src/hal/esp32s3.rs

@@ -1,8 +1,8 @@
 //! ESP32-S3 MCU initialization primitives.
 //!
-//! Provides low-level bus and peripheral init for ESP32-S3 boards.
+//! Provides low-level bus init for ESP32-S3 boards.
 //! Board files call these with specific pins and construct higher-level
-//! drivers (Sx126x, SSD1306, etc.) themselves.
+//! drivers (Sx126x, SSD1306, USB, UART, etc.) themselves.
 
 use embassy_sync::blocking_mutex::raw::NoopRawMutex;
 use esp_hal::dma::{DmaRxBuf, DmaTxBuf};
@@ -17,10 +17,6 @@ use static_cell::StaticCell;
 
 pub type SpiBus = SpiDmaBus<'static, esp_hal::Async>;
 pub type I2cBus = I2c<'static, esp_hal::Async>;
-#[allow(dead_code)] // Used by USB boards, not UART boards
-pub type UsbOtgDriver = esp_hal::otg_fs::asynch::Driver<'static>;
-#[allow(dead_code)] // Used by UART boards, not USB boards
-pub type UartDriver = esp_hal::uart::Uart<'static, esp_hal::Async>;
 
 // ── Timer ───────────────────────────────────────────────────────────
 
@@ -33,8 +29,6 @@ pub fn start_timer(timg0: esp_hal::peripherals::TIMG0<'static>) {
 // ── SPI bus ─────────────────────────────────────────────────────────
 
 /// Initialize SPI2 with DMA and wrap in a shared bus (StaticCell + Mutex).
-///
-/// Returns a reference to the shared SPI bus suitable for `SpiDevice::new()`.
 pub fn init_spi(
     spi2: esp_hal::peripherals::SPI2<'static>,
     dma_ch0: esp_hal::peripherals::DMA_CH0<'static>,
@@ -80,43 +74,6 @@ pub fn init_i2c(
         .into_async()
 }
 
-// ── USB OTG ─────────────────────────────────────────────────────────
-
-/// Initialize USB OTG FS driver for CDC-ACM.
-#[allow(dead_code)] // Used by USB boards, not UART boards
-pub fn init_usb(
-    usb0: esp_hal::peripherals::USB0<'static>,
-    dp: esp_hal::peripherals::GPIO20<'static>,
-    dm: esp_hal::peripherals::GPIO19<'static>,
-) -> UsbOtgDriver {
-    let usb_inst = esp_hal::otg_fs::Usb::new(usb0, dp, dm);
-    static EP_OUT_BUF: StaticCell<[u8; 1024]> = StaticCell::new();
-    let ep_out_buf = EP_OUT_BUF.init([0u8; 1024]);
-    esp_hal::otg_fs::asynch::Driver::new(
-        usb_inst,
-        ep_out_buf,
-        esp_hal::otg_fs::asynch::Config::default(),
-    )
-}
-
-// ── UART ────────────────────────────────────────────────────────────
-
-/// Initialize UART0 for boards with USB-UART bridge chips (e.g. CP2102).
-#[allow(dead_code)] // Used by UART boards, not USB boards
-pub fn init_uart(
-    uart0: esp_hal::peripherals::UART0<'static>,
-    tx: esp_hal::peripherals::GPIO43<'static>,
-    rx: esp_hal::peripherals::GPIO44<'static>,
-) -> UartDriver {
-    use esp_hal::uart::{Config as UartConfig, Uart};
-
-    Uart::new(uart0, UartConfig::default())
-        .expect("UART init")
-        .with_tx(tx)
-        .with_rx(rx)
-        .into_async()
-}
-
 // ── MAC address ─────────────────────────────────────────────────────
 
 /// Read the factory-programmed MAC address from eFuse.

src/host/uart.rs

@@ -6,7 +6,7 @@ use defmt::warn;
 use embassy_executor::task;
 use embedded_io_async::Write;
 
-use crate::channel::{CommandChannel, DisplayCommandChannel, ResponseChannel};
+use crate::channel::{CommandChannel, DisplayCommand, DisplayCommandChannel, ResponseChannel};
 use super::framing::{self, CobsDecoder, MAX_FRAME};
 
 #[task]
@@ -20,6 +20,11 @@ pub async fn host_task(
 ) {
     let (mut rx, mut tx) = parts.driver.split();
 
+    // UART has no DTR — signal the display that a host is present at boot.
+    if has_display {
+        display_commands.send(DisplayCommand::Reset).await;
+    }
+
     let mut read_buf = [0u8; 64];
     let mut write_buf = [0u8; MAX_FRAME];
     let mut cobs_encode_buf = [0u8; MAX_FRAME];

src/protocol.rs

@@ -277,12 +277,11 @@ impl Response {
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 #[cfg_attr(not(test), derive(defmt::Format))]
 #[repr(u8)]
-#[allow(dead_code)] // CrcError reserved per PROTOCOL.md (error code 3)
 pub enum ErrorCode {
     InvalidConfig = 0,
     RadioBusy = 1,
     TxTimeout = 2,
-    CrcError = 3,
+    // 3 reserved (was CrcError — SX1262 silently drops bad-CRC packets)
     NotConfigured = 4,
     NoDisplay = 5,
 }
@@ -686,7 +685,6 @@ mod tests {
             (ErrorCode::InvalidConfig, 0),
             (ErrorCode::RadioBusy, 1),
             (ErrorCode::TxTimeout, 2),
-            (ErrorCode::CrcError, 3),
             (ErrorCode::NotConfigured, 4),
             (ErrorCode::NoDisplay, 5),
         ] {