JC3636W518EN/10-OBD-Display-2024

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)

Split out of 2-Program Example/Demo_Arduino/ST77916_LVGL_DEMO/ on 2026-10-22 and converted to PlatformIO. History is in git.

Projects (all PlatformIO)

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/
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). LVGL 9.6.0, plays at full GIF speed (~23.4 fps), prints FPS once per second. GIF starts without SD card. WiFi code commented out.	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/
assets/gifs/	—	GIF files (dump/ = unused collection)	ST77916_LVGL_DEMO/gifs/
_archive/lvgl9_broken/	—	Unfinished LVGL 9 port, does not compile, not converted	ST77916_LVGL_DEMO/9.1/

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 (display_*): LVGL 9.6.0 and the shared board library/config in ../shared (see shared/README.md). Each platformio.ini only extends shared/jc3636w518.ini; display_gif_embedded additionally uses default_16MB.csv. All three print FPS / refresh / other / CPU once per second on serial (115200).
• 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_STDIO on /sdcard/ (the SD_MMC mount). Not yet verified with LVGL 9 on hardware (SD card was stuck during the port).
• display_speed_wifi polls /speed with a blocking HTTP request on every loop pass (unchanged from 2024) — slows the UI when WiFi is connected.