# Shared JC3636W518 code

Everything every JC3636W518 project needs, in one place:

| Path | What |
|---|---|
| `jc3636w518.ini` | Common PlatformIO settings: pioarduino 51.03.05 (Arduino core 3.0.5), ESP32-S3 16 MB QIO / OPI PSRAM, `huge_app.csv`, `-O2`, LVGL 9.6.0, vendor display libraries, COM21 |
| `include/lv_conf.h` | LVGL 9.6 config (generated from the 9.6 template; every change is marked `JC3636W518`) |
| `include/lv_attr_jc3636w518.h` | LVGL attribute overrides: hot functions and `lv_display_flush_ready()` in IRAM |
| `lib/JC3636W518/` | Board library: `jc3636w518.h` (display/touch/backlight init + LVGL glue), `pincfg.h` (pin map), `perf_monitor.h` (FPS/CPU monitor) |

## New project
```ini
; platformio.ini
[platformio]
extra_configs = ../shared/jc3636w518.ini   ; path to this folder

[shared]
dir = ../shared                            ; same path

[env:jc3636w518]
extends = jc3636w518
; project-specific overrides, e.g. board_build.partitions = default_16MB.csv
```
```cpp
#include <Arduino.h>
#include "jc3636w518.h"
#include "perf_monitor.h"   // optional

void setup() {
  Serial.begin(115200);
  lv_display_t *disp = scr_lvgl_init();   // also does lv_init()
  perf_monitor_begin(disp);              // optional
  // ... create LVGL UI ...
}

void loop() {
  perf_timer_handler();                  // or lv_timer_handler()
  vTaskDelay(1);
  perf_monitor_print();                  // optional: FPS / refresh / other / CPU once per second
}
```
Add `-DJC_DRAW_BUF_ROWS=<n>` to `build_flags` (as `${jc3636w518.build_flags}` + extra line) to change the draw buffer height (default 72).

## Performance settings (measured with `display_gif_embedded`, 360×360 GIF at 23.7 fps)
| Setting | Effect |
|---|---|
| LVGL 9.6 (AnimatedGIF decoder) | GIF decode 24 → 12 ms per frame vs LVGL 8.3 |
| Two 72-row draw buffers in internal RAM | render while the previous chunk is sent (120 rows: no gain) |
| `LV_COLOR_FORMAT_DEFAULT = RGB565_SWAPPED` | renders in the ST77916 byte order → no swap pass in flush |
| QSPI 80 MHz (was 50) | faster transfer to the panel |
| `-O2`, IRAM for hot LVGL functions | faster rendering/decoding |
| GIF in display color format (`lv_gif_set_color_format`) | per sketch, only when the GIF needs no transparency (plain background) |

Result: CPU for the GIF 86 % → 53 % at full frame rate.

## Display / LVGL facts
- Display format is `RGB565_SWAPPED`. For images/canvases you create yourself, use `lv_display_get_color_format(disp)` or ARGB8888 when transparency is needed.
- LVGL drive `A:` = SD card (`LV_USE_FS_STDIO`, path `/sdcard/`); mount the card with `SD_MMC` first.
- `LV_USE_STDLIB_MALLOC = CLIB`: LVGL uses `malloc`, so large allocations land in PSRAM. `lv_mem_monitor()` reports 0 in this mode.