feat(boards): Add Waveshare ESP32-C6-Touch-AMOLED-2.16 support

- Add complete board support for Waveshare ESP32-C6-Touch-AMOLED-2.16 with SH8601 display driver
- Implement board initialization with AXP2101 PMU rail configuration for LCD and touch power
- Add display driver for SH8601 QSPI panel (480×480 resolution)
- Add CST9217 touch controller support via I2C
- Add QMI8658 IMU initialization and sensor reading
- Add AXP2101 power management and battery monitoring
- Add input handling for BOOT button (GPIO 9)
- Configure PlatformIO environment with C6-specific build flags and 16 MB flash layout
- Update capability flags documentation to clarify BOARD_HAS_PSRAM build-flag macro usage
- C6 has no external PSRAM; shared code gates on this flag to use internal SRAM and reduce LVGL buffer sizes
- Screenshot capture disabled on this board due to internal SRAM constraints

firmware/platformio.ini

@@ -109,3 +109,71 @@ lib_deps =
     lvgl/lvgl@^9.2.0
     bblanchon/ArduinoJson@^7.0.0
     h2zero/NimBLE-Arduino@^2.1.1
+
+
+[env:waveshare_amoled_216_c6]
+; C6 sibling of the AMOLED-2.16. Same panel/touch/PMU/IMU, no PSRAM,
+; single-core RISC-V, BLE 5.3 only (no classic BT). If the build fails
+; resolving the C6 board, bump pioarduino to a newer 55.x release that
+; ships esp32-c6-devkitc-1.
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/55.03.38-1/platform-espressif32.zip
+board = esp32-c6-devkitc-1
+framework = arduino
+upload_speed = 921600
+monitor_speed = 115200
+; Waveshare's C6-AMOLED-2.16 ships with 16 MB flash. The default 1.25 MB
+; app partition can't hold this firmware (~1.43 MB) — switch to the
+; 16 MB layout that gives the app ~6.5 MB, matching the AMOLED-1.8 env.
+board_upload.flash_size = 16MB
+board_upload.maximum_size = 16777216
+board_build.partitions = default_16MB.csv
+
+build_src_filter =
+    +<*>
+    -<boards/>
+    +<boards/waveshare_amoled_216_c6/>
+
+build_flags =
+    -DBOARD_AMOLED_216_C6
+    ; C6 has only USB-Serial-JTAG (HWCDC), no native USB-OTG. The Arduino
+    ; core maps Serial → HWCDCSerial only when BOTH flags below are set;
+    ; CDC_ON_BOOT alone selects USBSerial (TinyUSB) which doesn't exist on
+    ; C6 and breaks the build. Without either flag, Serial routes to UART0
+    ; on physical pins and nothing reaches the USB host.
+    -DARDUINO_USB_CDC_ON_BOOT=1
+    -DARDUINO_USB_MODE=1
+    ; No -DBOARD_HAS_PSRAM — C6 has no external PSRAM. Shared code
+    ; (main.cpp, splash.cpp) gates on this to pick MALLOC_CAP_INTERNAL
+    ; and shrink LVGL buffers + splash canvas accordingly.
+    -DXPOWERS_CHIP_AXP2101
+    -DCONFIG_BT_NIMBLE_ROLE_BROADCASTER=1
+    -DCONFIG_BT_NIMBLE_ROLE_PERIPHERAL=1
+    -DCONFIG_BT_NIMBLE_ROLE_CENTRAL=0
+    -DCONFIG_BT_NIMBLE_ROLE_OBSERVER=0
+    -DCONFIG_BT_NIMBLE_MAX_CONNECTIONS=2
+    -DLV_CONF_SKIP
+    -DLV_COLOR_DEPTH=16
+    -DLV_USE_LOG=0
+    -DLV_USE_BAR=1
+    -DLV_USE_LABEL=1
+    -DLV_USE_ARC=1
+    -DLV_USE_BTN=1
+    -DLV_USE_LINE=1
+    -DLV_USE_OBJ=1
+    -DLV_USE_IMG=1
+    -DLV_USE_IMAGE=1
+    -DLV_USE_ANIMIMG=0
+    -DLV_TICK_CUSTOM=1
+    ; Screenshot capture needs a full-frame RGB565 buffer (~460 KB on
+    ; 480×480) which doesn't fit in C6 internal SRAM. send_screenshot
+    ; prints SCREENSHOT_UNSUPPORTED on this board.
+    -DLV_USE_SNAPSHOT=0
+
+lib_deps =
+    ; 1.6.4+ required for Arduino_SH8601 (this board uses SH8601, not CO5300)
+    moononournation/GFX Library for Arduino@^1.6.4
+    lewisxhe/SensorLib@^0.2.6
+    lewisxhe/XPowersLib@^0.2.7
+    lvgl/lvgl@^9.2.0
+    bblanchon/ArduinoJson@^7.0.0
+    h2zero/NimBLE-Arduino@^2.1.1