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# OBD Display (2024 experiments)
Earlier attempt to show car speed from an ELM327 OBD-II adapter on the JC3636W518.
Because the ESP32-S3 has no Bluetooth Classic, the design used a second (classic) ESP32 as a bridge:
```
ELM327 --(BT Classic SPP)--> classic ESP32 (elm327_wifi_bridge) --(WiFi AP, HTTP /speed)--> JC3636W518 (display_speed_wifi)
```
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Split out of `2-Program Example/Demo_Arduino/ST77916_LVGL_DEMO/` on 2026-10-22 and converted to PlatformIO. History is in git.
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## Projects (all PlatformIO)
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| Folder | Runs on | What it does | Was |
|---|---|---|---|
| `display_speed_wifi/` | JC3636W518 | GIF background from SD (`A:wallpaper.gif` ) + joins AP `ESP32-Access-Point` , polls `http://192.168.4.1/speed` , shows it in a label | `ST77916_LVGL_DEMO/8.4/` |
| `display_gif_sd/` | JC3636W518 | GIF from SD (`A:wallpaper.gif` ) + static text label | `ST77916_LVGL_DEMO/working version/` |
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| `display_gif_embedded/` | JC3636W518 | GIF compiled into firmware (`src/loligod.c` , 2.2 MB GIF → 3.4 MB firmware, uses `default_16MB.csv` with 6.25 MB app slots). WiFi code commented out. Stops in `setup()` if no SD card | `ST77916_LVGL_DEMO/` (top level) |
| `elm327_wifi_bridge/` | **classic ESP32** (not S3) | BT Classic → ELM327 named `OBDII` (PIN 1234), WiFi AP `ESP32-Access-Point` / `123456789` , serves `/speed` (kph) | `ST77916_LVGL_DEMO/esp23_elm327_to_wifi/` |
| `elmulator/` | classic ESP32 | Fake ELM327 for testing without a car. Library in `lib/ELMulator` , envs `simple` , `custom` , `wifi` (BT name `OBDII` ) | `ST77916_LVGL_DEMO/ELMulator-master/` |
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| `assets/gifs/` | — | GIF files (`dump/` = unused collection) | `ST77916_LVGL_DEMO/gifs/` |
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| `_archive/lvgl9_broken/` | — | Unfinished LVGL 9 port, does not compile, not converted | `ST77916_LVGL_DEMO/9.1/` |
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## Build / upload
Open a project folder in VS Code with the PlatformIO extension, or from a terminal:
```
pio run -d display_speed_wifi # build
pio run -d display_speed_wifi -t upload # flash (COM21)
pio device monitor -d display_speed_wifi # serial monitor
pio run -d elmulator -e wifi -t upload --upload-port COMxx
```
(`pio` = `%USERPROFILE%\.platformio\penv\Scripts\pio.exe` if not on PATH.)
## Configuration
- **JC3636W518 projects:** pioarduino platform `51.03.05` (= Arduino core 3.0.5), board `esp32-s3-devkitc-1` with 16 MB QIO flash, OPI PSRAM, `huge_app.csv` (3 MB app), USB-CDC on boot, COM21.
Libraries come from the vendor folder via `lib_extra_dirs = ../../2-Program Example/Demo_Arduino/library` .
Each project uses its **own `include/lv_conf.h`** (`-DLV_CONF_INCLUDE_SIMPLE -Iinclude` ):
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- `display_speed_wifi` : LVGL heap 4 MB in PSRAM (`ps_malloc` )
- `display_gif_sd` : LVGL heap 7 MB in PSRAM
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- **Classic ESP32 projects:** official `espressif32@6.10.0` (Arduino core 2.0.17), board `esp32dev` , `huge_app.csv` . Set `upload_port` to the classic ESP32's COM port.
Bridge libraries: `powerbroker2/ELMduino@3.4.1` , `esphome/ESPAsyncWebServer-esphome@3.4.0` .
## Notes
- `src/montserrat_100.c` (100 px digits font) is present but not referenced by any sketch yet.
- SD-based GIFs use LVGL drive `A:` = `LV_USE_FS_FATFS` (reads through ESP-IDF FatFS on the SD_MMC mount). Not yet verified on hardware.
