## PlatformIO setup (preferred build system, since 2026-10-23)
- All projects are **PlatformIO projects** (`platformio.ini`, `src/main.cpp`, `include/`). They no longer open in the Arduino IDE.
- PlatformIO IDE extension is installed in VS Code. CLI: `%USERPROFILE%\.platformio\penv\Scripts\pio.exe` (Core 6.2.0, not on PATH).
- **JC3636W518 (ESP32-S3)**: platform `https://github.com/pioarduino/platform-espressif32/releases/download/51.03.05/platform-espressif32.zip` (pioarduino = Arduino core 3.0.5; the official PIO espressif32 only has core 2.x, which ESP32_Display_Panel 0.1.4 can't use).
**All of this lives in `shared/jc3636w518.ini`**; a project's `platformio.ini` only does `extra_configs` + `[shared] dir` + `extends = jc3636w518` (see `shared/README.md`).
Libraries: `lib_deps = lvgl/lvgl@9.6.0`, `lib_extra_dirs` → `shared/lib` (board library) + vendor `2-Program Example/Demo_Arduino/library` (ESP32_Display_Panel, ESP32_IO_Expander; its lvgl 8 is not used).
**LVGL config:**`-DLV_CONF_INCLUDE_SIMPLE -I${shared.dir}/include` — the `-I` is required, otherwise the LVGL library compiles without `lv_conf.h` (symptom: `undefined reference to lv_gif_create`).
- (Classic ESP32 projects — the 2024 BT-Classic→WiFi bridge and ELMulator — were removed 2026-10-23; they used `espressif32@6.10.0`, board `esp32dev`. In git history.)
- When converting `.ino` → `main.cpp`: add `#include <Arduino.h>` and prototypes for functions used before their definition; don't `#include``.c` files that are also in `src/`.
## Software stack used by the vendor demo
- **Arduino IDE** + **arduino-esp32 core ≥ 3.0.1** (core **3.0.5 already installed** on this PC under `%LOCALAPPDATA%\Arduino15`).
- Libraries (bundled in `2-Program Example/Demo_Arduino/library/`):
-`lvgl`**8.3.11** bundled (instructions say "8.4.0 and below"; LVGL 9 is NOT supported by the demo)
-`lv_conf.h` must be copied next to the `lvgl` library folder (`Documents\Arduino\libraries\lv_conf.h`); for the LVGL demos, move `lvgl/demos` into `lvgl/src/`.
- None of these libraries are currently in `Documents\Arduino\libraries` (only unrelated Adafruit libs). No arduino-cli / PlatformIO / ESP-IDF installed. Python 3.12 and git are available.
### Arduino board settings (from `Arduino set up.png`)
Board **ESP32S3 Dev Module**, USB CDC On Boot **Enabled**, CPU 240 MHz, Flash **QIO 120 MHz**, Flash Size **16 MB**,
Helpers: `setRotation(0..3)` / `getRotation()` (panel rotates via MADCTL swap/mirror like the vendor table; touch converted in software in `touchpad_read`; **verified by the user at all 4 angles**, 2026-10-23), `set_brightness(0..100)`, `screen_switch(bool)`; `perf_monitor.h` prints FPS/refresh/other/CPU once per second.
| `shared` | **Shared code for all JC3636W518 projects:**`jc3636w518.ini` (PlatformIO base config), `include/lv_conf.h` (LVGL 9.6), `lib/JC3636W518` (board library). See its `README.md` |
| `12-OBD-Speed` | **The new program — working in the car (2026-10-23):** speed from the ELM327 over BLE as big number + arc gauge on a GIF background, battery-voltage arc in the bottom gap, idle/screen-off mode (both **verified by the user**); swipe left for the adapter menu (scan, select → remembered in NVS, auto-reconnect every 3 s), again for settings (rotation, idle/screen-off timeout), again for the background (GIF from SD `/gifs` copied into an 11.9 MB raw flash partition, own `partitions.csv`). See its `README.md` |
| `10-GIF-Tests` | **GIF playback experiments** (was `10-OBD-Display-2024`): `display_gif_embedded`, `display_gif_sd`, `assets/gifs`. The 2024 bridge/ELMulator/WiFi speed sketch, the broken LVGL 9 archive and the BLE scanner tool (`11-BLE-Scanner`: on-screen scan, GATT listing, ELM test, LittleFS log) were removed 2026-10-23 — all in git history |
| `8-Tool` | Network debugging assistant, SSCOM serial tool (Chinese Windows tools, .rar) |
| `9-Burn` | Espressif Flash Download Tool 3.9.3, factory demo `1.85_demo.bin` (1.7 MB, flash at 0x0), screenshots. `logs/` are old (2022) logs from other boards — ignore |
## Factory firmware (for reference)
AIDA64 secondary screen (18 styles), mic spectrum, MP3 player (`/music` on SD), photo frame (`/pic`, 360×360 JPEG), MJPEG player (`/mjpeg`), weather, theme clocks, WiFi provisioning AP "My App"/12345678 + web config at device IP.
Re-flash it with Flash Download Tool: ESP32-S3, `1.85_demo.bin` @ 0x0.
Cheap ELM327 clones draw ~20–50 mA permanently (OBD pin 16 = always 12 V); the display ~180 mA if its USB stays powered. `12-OBD-Speed` idle mode stops OBD polling after N min without data so the car's ECUs can sleep; `ATRV` (adapter-internal) every 30 s detects an engine start (> 13.2 V).
AliExpress "ELM327 Mini V2.1 Bluetooth OBD **Dual Mode** 5.1" — dual mode = Bluetooth Classic SPP **and BLE**, so the ESP32-S3 should be able to connect directly over BLE (no bridge ESP32).
- **LVGL 8 GIF bug (patched locally, only relevant if LVGL 8 is used again):** LVGL 8.3.11 `gifdec.c` (`gd_open_gif`) filled the canvas *opaque* with the GIF's background color. GIFs with a transparent background (e.g. `loligod.gif`, bg = RGB 28,29,49) showed that dark gray except where "restore to background" frames had cleared to transparent (→ screen black). **Patched** in the vendor copy `2-Program Example/Demo_Arduino/library/lvgl/src/extra/libs/gif/gifdec.c`: initial canvas alpha 0x00 (marked `LOCAL PATCH`). Re-apply if LVGL is ever replaced/upgraded.
- Most GIFs in `assets/gifs` are optimized (transparent unchanged pixels, disposal 1/2); `loligod.gif` has a fully transparent background (~84 % of each frame).
- **GIF performance** (360×360 loligod, embedded, measured with a `monitor_cb` FPS counter in `display_gif_embedded`):
baseline 15.4 fps (decode 27 ms + refresh 31 ms) → no LVGL log / no per-loop prints: no change → `vTaskDelay(1)`: 16.5 → **double draw buffer** (2×72 rows internal RAM): 19.5 (refresh 21 ms) → **`-O2`** instead of `-Os`: **20.6 fps** (refresh 19 ms, decode ~24 ms). GIF's own rate is 23.7 fps. From SD card it was only ~1.4 fps.
Remaining limit is LVGL's single-threaded GIF decode; going further would need decoding on the other core or a lighter format (e.g. pre-converted frames/MJPEG).
- **SD card (user's 487 MB SDSC)** intermittently fails to init (`sdmmc_init_ocr ... 0x107`) after resets; once stuck only a power cycle helps (card VDD is hard-wired to 3V3). Recommend a newer SDHC card.
- Reading boot logs: USB-CDC — reset via DTR=0/RTS pulse, then reopen the port (it re-enumerates).
- **LVGL 9.6.0 port** (`display_gif_embedded`, 2026-10-23): **23.4 fps** (= the GIF's own 23.7 fps; decode ~12 ms, refresh ~24 ms) vs 20.6 fps tuned LVGL 8.3. LVGL 9.6 replaced gifdec with bitbank2 AnimatedGIF (2× faster decode, correct transparency — no local patch needed).
Port notes: `lib_deps = lvgl/lvgl@9.6.0` (takes priority over the vendor lvgl 8 in `lib_extra_dirs`); `lv_conf.h` generated from the 9.6 template (CLIB malloc, refresh 15 ms, GIF on, examples off); in 9.6 public headers live in `include/lvgl/` and `LV_COLOR_DEPTH` is deprecated → `LV_COLOR_FORMAT_DEFAULT` (RGB565); no LV_COLOR_16_SWAP → `lv_draw_rgb565_swap()` in the flush cb; no LV_TICK_CUSTOM → `lv_tick_set_cb(millis)`; no `monitor_cb` → display events `LV_EVENT_REFR_START/RENDER_START/REFR_READY`; images are `lv_image_dsc_t` with `LV_IMAGE_HEADER_MAGIC`. `lv_gif_set_color_format()` switches the GIF buffer format (used, see below).
- **LVGL 9 tuning** (display_gif_embedded, CPU at full 23.8 fps): start 86 % → GIF in display color format 66 % → render `RGB565_SWAPPED` (no swap pass) 60 % → QSPI 80 MHz 55 % → IRAM for hot LVGL code 53 %. No effect: `LV_GIF_CACHE_DECODE_DATA` (not used anywhere in 9.6), 120-row buffers. AnimatedGIF "turbo" mode can't be used: it only outputs in COOKED draw mode, LVGL uses RAW.
- **All JC3636W518 LVGL projects now use LVGL 9.6.0 + the shared library** (10-GIF-Tests/*, 12-OBD-Speed). SD drive `A:` = `LV_USE_FS_STDIO` on `/sdcard/`.
- Draw buffer is in internal RAM; PSRAM is available for larger buffers / images.
- **LittleFS** works on the `spiffs` partition of `huge_app.csv` (~900 KB); the first mount after flashing formats it (prints `Corrupted dir pair` / `mount failed (-84)` and some `task_wdt ... task not found` once — harmless).
- BLE (NimBLE) in the user's home: ~12 devices visible within 10 s.
- Big fonts: generate with `npx lv_font_conv` (Node 22 installed) from `lvgl/scripts/generators/built_in_font/Montserrat-Medium.ttf`; `-DLV_LVGL_H_INCLUDE_SIMPLE` (in shared ini) makes the generated `#include` work.
- Binary assets (GIFs): `board_build.embed_files = data/x.gif` → `extern const uint8_t x_start[] asm("_binary_data_x_gif_start")` (no huge C arrays).
- Python edit scripts: never pass C strings containing `\n` through a bash heredoc into Python — it turned into a real line break twice; write the script with the Write tool instead.
- Serial output from the background task (core 0) is often lost, not only right after reset; don't rely on it as proof. Serial output right after a reset can be lost/garbled (USB-CDC re-enumeration, prints from two cores interleave) — don't conclude a task isn't running from a missing early line.
