chore: release 1.3.1

The classic T-Beam's red LED on GPIO4 is wired active-low (anode to V+,
cathode to GPIO). Release v1.3.0 drove it as active-high, so the LED sat
lit at idle and dimmed briefly on TX/RX instead of flashing on activity.

Express the polarity where it physically lives — at the pin — via a new
generic InvertedPin<P> wrapper that swaps set_high/set_low. SimpleLed
stays polarity-agnostic and every other board's code path is
byte-for-byte unchanged from v1.3.0.

Empirically verified against hardware on both T-Beam boards: classic red
LED is now dark at idle and flashes on TX/RX; Supreme blue LED behaves
unchanged.

CHANGELOG.md

@@ -7,6 +7,24 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 
 ## [Unreleased]
 
+## [1.3.1] - 2026-04-23
+
+### Fixed
+
+- **LilyGo T-Beam (classic) red LED now flashes on TX/RX** instead of
+  dimming off. The red LED under the OLED is wired active-LOW on this
+  board (anode to V+, cathode to GPIO4); v1.3.0 drove it as active-HIGH,
+  so the LED sat lit at idle and briefly dimmed during activity.
+  - Empirically verified on hardware against both T-Beam variants.
+  - Introduces `src/driver/inverted_pin.rs::InvertedPin<P>`, a generic
+    `OutputPin` wrapper that swaps `set_high`/`set_low`. Polarity is
+    expressed at the pin (where the physical wiring lives), so
+    `SimpleLed` stays polarity-agnostic and every other board's code
+    path is byte-for-byte unchanged.
+  - Classic T-Beam now constructs its LED as
+    `SimpleLed(InvertedPin(led_pin))` with pin init at `Level::High`
+    (dark at boot).
+
 ## [1.3.0] - 2026-04-23
 
 ### Added

Cargo.lock

@@ -486,7 +486,7 @@ dependencies = [
 
 [[package]]
 name = "donglora"
-version = "1.3.0"
+version = "1.3.1"
 dependencies = [
  "cfg-if",
  "cortex-m",

Cargo.toml

@@ -3,7 +3,7 @@ members = ["."]
 
 [package]
 name = "donglora"
-version = "1.3.0"
+version = "1.3.1"
 edition = "2021"
 build = "build.rs"
 authors = ["Stephen Waits <steve@waits.net>"]

src/board/lilygo_tbeam.rs

@@ -13,7 +13,8 @@
 //!   LoRa ctl:  RESET=23, DIO0=26 (primary IRQ — SX127x has no BUSY)
 //!   OLED I²C:  SDA=21, SCL=22, SSD1306 @ 0x3C (shared with AXP192 @ 0x34)
 //!   UART host: TX=1, RX=3 via CP2102 bridge (USB 10c4:ea60)
-//!   LED:       GPIO4 (active HIGH — reuses MeshCore's P_LORA_TX_LED)
+//!   LED:       GPIO4 (active LOW — red LED under the OLED, wrapped in
+//!              InvertedPin so SimpleLed sees normal polarity)
 //!
 //! GPS / battery / IMU / PCF8563 RTC are populated on the board but unused
 //! by this firmware.
@@ -24,6 +25,7 @@ use esp_hal::i2c::master::{Config as I2cConfig, I2c};
 use super::esp32;
 use super::traits::{BoardParts, LoRaBoard};
 use crate::driver::axp;
+use crate::driver::inverted_pin::InvertedPin;
 use crate::driver::simple_led::SimpleLed;
 use crate::hal::esp32 as mcu;
 use crate::protocol::RadioChipId;
@@ -33,7 +35,7 @@ pub use super::esp32::{create_display, DisplayDriver, DisplayParts, RadioDriver,
 // ── Concrete peripheral types ───────────────────────────────────────
 
 pub type UartDriver = esp_hal::uart::Uart<'static, esp_hal::Async>;
-pub type LedDriver = SimpleLed<Output<'static>>;
+pub type LedDriver = SimpleLed<InvertedPin<Output<'static>>>;
 
 // ── Peripheral bundles ──────────────────────────────────────────────
 
@@ -122,9 +124,10 @@ impl LoRaBoard for Board {
             i2c: i2c_blocking.into_async(),
         });
 
-        // TX activity LED on GPIO4 (active HIGH).
-        let led_pin = Output::new(p.GPIO4, Level::Low, OutputConfig::default());
-        let led = SimpleLed(led_pin);
+        // TX activity LED on GPIO4 (active LOW — pin idles HIGH = LED off).
+        // InvertedPin flips set_high/set_low so SimpleLed stays polarity-agnostic.
+        let led_pin = Output::new(p.GPIO4, Level::High, OutputConfig::default());
+        let led = SimpleLed(InvertedPin(led_pin));
 
         BoardParts {
             radio,

src/driver/inverted_pin.rs

@@ -0,0 +1,30 @@
+//! Generic `OutputPin` wrapper that inverts logic levels.
+//!
+//! When a peripheral is wired active-low (LED anode to V+, cathode to GPIO;
+//! reset line idle-high, etc.) the physical polarity is a property of the
+//! board, not of the driver. Wrapping the pin in `InvertedPin` lets drivers
+//! keep "set_high = assert" semantics while the board file expresses the
+//! wiring reality at construction time.
+//!
+//! ```ignore
+//! let pin = Output::new(p.GPIO4, Level::High, OutputConfig::default()); // off
+//! let led = SimpleLed(InvertedPin(pin)); // driver sees normal polarity
+//! ```
+
+use embedded_hal::digital::{ErrorType, OutputPin};
+
+pub struct InvertedPin<P>(pub P);
+
+impl<P: ErrorType> ErrorType for InvertedPin<P> {
+    type Error = P::Error;
+}
+
+impl<P: OutputPin> OutputPin for InvertedPin<P> {
+    fn set_low(&mut self) -> Result<(), Self::Error> {
+        self.0.set_high()
+    }
+
+    fn set_high(&mut self) -> Result<(), Self::Error> {
+        self.0.set_low()
+    }
+}

src/driver/mod.rs

@@ -8,6 +8,9 @@ pub mod sh1106;
 #[cfg(any(feature = "lilygo_tbeam_supreme", feature = "lilygo_tbeam"))]
 pub mod axp;
 
+#[cfg(feature = "lilygo_tbeam")]
+pub mod inverted_pin;
+
 #[cfg(any(
     feature = "heltec_v3",
     feature = "heltec_v3_uart",