## Build Options and flags

This library supports build-time defines to modify its features or enable greater debugging information. Please use the debugging capabilities before raising any issues. 

### When using PlatformIO
For example build flags could be set using PlatformIO's  .ini file like this

```
[env]
framework = arduino
platform = espressif32
lib_deps =
    ESP32 HUB75 LED MATRIX PANEL DMA Display
build_flags =
    -DCORE_DEBUG_LEVEL=3
    -DNO_GFX=1
    (etc.....)
```

### When using the Arudino IDE
It is possible to set compile-time  options when using Arduino by creating a file called "build_opt.h" in the Arudino Sketch folder.

This file would contain compile-time options in a format on a seperate line. e.g: `-DNO_GFX=1`

Refer to: https://github.com/stm32duino/Arduino_Core_STM32/wiki/Customize-build-options-using-build_opt.h


## Build flags

| Flag  | Description  | Note |
| :------------ |---------------|-----|
| **CORE_DEBUG_LEVEL** |Adjust the espressif ESP32 IDF debug level, for which this library leverages to output information on what is going on when allocating memory etc. This will provide detailed information about memory allocations, DMA descriptors setup and color depth [BCM](http://www.batsocks.co.uk/readme/art_bcm_5.htm) |Set value to at least 3 [(Info)](https://iotespresso.com/core-debug-level-in-esp32/)
| **USE_GFX_LITE** | Use my [customised library](https://github.com/mrcodetastic/GFX_Lite) that is a combination of AdaFruit_GFX and FastLED. | You **must** have the [GFX_Lite](https://github.com/mrcodetastic/GFX_Lite) library downloaded (installed) in your compile path when using this option of course. |
| **NO_GFX** | Build without AdafuitGFX API, only native methods supported based on manipulating DMA buffer. I.e. no methods of drawing circles/shapes, typing text or using fonts!!!    This might save some resources for applications using it's own internal graphics buffer or working solely with per-pixel manipulation.  |   Use this if you rely on FastLED, Neomatrix or any other API. For example [Aurora](/examples/AuroraDemo/) effects can work fine w/o AdafruitGFX. |
| **NO_FAST_FUNCTIONS** | Do not build auxiliary speed-optimized functions. Those are used to speed-up operations like drawing straight lines or rectangles. Otherwise lines/shapes are drawn using drawPixel() method. The trade-off for speed is RAM/code-size, take it or leave it ;)        | If you are not using AdafruitGFX than you probably do not need this either|
|**NO_CIE1931**|Do not use LED brightness [compensation](https://ledshield.wordpress.com/2012/11/13/led-brightness-to-your-eye-gamma-correction-no/) described in [CIE 1931](https://en.wikipedia.org/wiki/CIE_1931_color_space). Normally library would adjust every pixel's RGB888 so that luminance (or brightness control) for the corresponding LED's would appear 'linear' to the human's eye. I.e. a white dot with rgb(128,128,128) would seem to be at 50% brightness between rgb(0,0,0) and rgb(255,255,255). Normally you would like to keep this enabled by default. Not only it makes brightness control "linear", it also makes colours more vivid, otherwise it looks brighter but 'bleached'.|You might want to turn it off in some special cases like: <ul><li>Using some other overlay lib for intermediate calculations that makes it's own compensation, like FastLED's [dimming functions](http://fastled.io/docs/3.1/group___dimming.html).<li>running at low colour depth's - it **might** (or might not) look better in shadows, darker gradients w/o compensation, try it<li>you run for as bright output as possible, no matter what (make sure you have proper powering)<li>you run for speed/save resources at all costs</ul> |
| **FORCE_COLOR_DEPTH** |In some cases the library may reduce colour fidelity to increase the refresh rate (i.e. reduce visible flicker). This is most likely to occur with a large chain of panels. However, if you want to force pure 24bpp colour, at the expense of likely noticeable flicker, then set this defined. |Not required in 99% of cases.
| **SPIRAM_FRAMEBUFFER** |Use SPIRAM/PSRAM for the HUB75 DMA buffer and not internal SRAM. ONLY SUPPORTED ON ESP32-S3 VARIANTS WITH OCTAL (not quad!) SPIRAM/PSRAM, as ony OCTAL PSRAM an provide the required data rate / bandwidth to drive the panels adequately.|ONLY SUPPORTED ON ESP32-S3 VARIANTS WITH OCTAL (not quad) SPIRAM/PSRAM

## Build-time variables

| Flag  | Description  | Note |
| :------------ |---------------|-----|
| **PIXEL_COLOR_DEPTH_BITS=8** | Colour depth per pixel in range 2-8. More bit's - more natural colour. But on the other hand every additional bit:<ul><li>eats ~2.5 bits of DMA memory per pixel<li>reduces matrix refresh rate in power of two due to nature of [BCM](http://www.batsocks.co.uk/readme/art_bcm_5.htm)</ul>  | For large chains of panels (i.e. 6 x 64x64 panels) you WILL need to reduce the colour depth, or likely run out of memory. Default is 8 bits per colour per pixel, i.e. True colour 24 bit RGB. <br><br>For higher resolutions, from 64x64 and above it is not possible to provide full 24 bits colour without significant flickering OR reducing dynamic range in shadows. In that case using 5-6 bits at high res make very small difference to the human’s eye actually. Refer to the [I2S memcalc](i2s_memcalc.md) for more details.
