Custom 96px font was not rendering because lv_font_conv defaults
to compressed bitmap format (bitmap_format=1) which requires
LV_USE_FONT_COMPRESSED. Regenerated with --no-compress.
Eliminated scroll tearing by switching from partial-strip rendering
to full-frame double buffering (LV_DISPLAY_RENDER_MODE_FULL).
Each buffer is 412KB in PSRAM (824KB total). Removes the need for
a separate byte-swap buffer — using LV_COLOR_FORMAT_RGB565_SWAPPED
so LVGL renders directly in the display's native byte order.
Also: hidden tileview scrollbar, enabled PSRAM in build flags.
LVGL 9.5.0 integration replacing direct framebuffer rendering.
Watch face with time, date, status bar (mode/battery), and three
complications (LoRa/GPS/Steps). Tileview swipe navigation between
five screens: watch face, radio status, GPS, messages, settings.
Haptic feedback on screen transitions via DRV2605.
Radio status screen shows frequency, LoRa params, RSSI bar gauge,
channel utilization, BLE state, and packet counts. GPS screen shows
coordinates, fix quality, altitude/speed, and beacon status.
Serial screenshot tool (scripts/screenshot.py) captures display
contents over USB CDC by sending trigger bytes and receiving the
shadow framebuffer as raw RGB565.
Build changes:
- FlashSize=16M in FQBN (bootloader embeds flash size, defaults 4MB)
- PSRAM=enabled for LVGL draw buffers and screenshot shadow buffer
- Custom 8MB app partition (partition_twatch.csv) for 16MB flash
- flash-twatch_ultra-full make target for full bootloader+partition+app flash
Architecture notes in code:
- display_init() must run BEFORE xl9555_init() (display power gate
defaults high at power-on, reordering causes black screen)
- LVGL draw buffers use separate swap buffer for RGB565 byte-order
conversion to avoid corrupting LVGL's internal buffer state
- Touch input registered via function pointer to decouple Gui.h from
touch library include order
