First RP2040 board and third MCU family (after ESP32-S3 and nRF52840).
Hardware: RP2040 + SX1262 radio, 850-930 MHz HF, PE4259 antenna switch,
LED on GPIO25, no OLED, USB-C via FPC ribbon cable to adapter board.
New files:
- src/hal/rp2040.rs: MCU primitives (SPI bus, USB driver, flash unique ID MAC)
- src/board/waveshare_rp2040_lora.rs: board implementation
- ld/rp2040-memory.x: linker memory layout
Also fixes cortex-m-rt/set-vtor (moved from global dep to per-board feature,
since Cortex-M0+ has no VTOR register) and makes build.rs memory.x selection
target-aware.
The default heltec_v3 feature now uses native USB OTG (same as V4),
appearing as /dev/ttyACM0 with the DongLoRa VID:PID (1209:5741).
This requires a hardware mod: solder R29/R3 and disconnect the CP2102
from the USB data lines.
Stock (unmodified) V3 boards should use the new heltec_v3_uart feature
which preserves the original UART-over-CP2102 behavior (/dev/ttyUSB0).
- heltec_v3: switched from UART to USB OTG
- heltec_v3_uart: new feature, UART fallback for stock boards
- Removed #[cfg] gates on UsbParts/UartParts (both always defined)
- Updated README with hardware mod instructions and board table
- Updated justfile with heltec_v3_uart board definition
swaits