How to get custom colors on SSD1331 RGB OLED Display

Other Hardware Displays
1

I'm using a SSD1331 RGB OLED Display such as this one.

In the example code, the colors are preset using 4-digit hex code like this:

#define	BLACK           0x0000
#define	BLUE            0x001F
#define	RED             0xF800
#define	GREEN           0x07E0
#define CYAN            0x07FF
#define MAGENTA         0xF81F
#define YELLOW          0xFFE0
#define WHITE           0xFFFF

How do I use a 6-digit hex code for the color instead of 4-digit? Is it possible? Do I need a different library instead of the Adafruit GFX one? Thanks!

2

You don't quote the library name. I don't want to guess.
There will be an existing library function.

Your 6 digit hex code in binary

RRRRRRRRGGGGGGGGBBBBBBBB  24bits
RRRRR---GGGGGG--BBBBB---  16bits
3

Ok, so binary works! Thank you for the help!

4

Go on. Is it really that difficult to say which library you are using?

Then you could use the proper library function.

5

I believe it's the Adafruit GFX library. Is there an existing library function for using a 6-digit hex?

6

Adafruit color display libraries have a method for converting to 16-bit color e.g. from https://github.com/adafruit/Adafruit-GFX-Library/blob/master/Adafruit_SPITFT.cpp

/*!
    @brief   Given 8-bit red, green and blue values, return a 'packed'
             16-bit color value in '565' RGB format (5 bits red, 6 bits
             green, 5 bits blue). This is just a mathematical operation,
             no hardware is touched.
    @param   red    8-bit red brightnesss (0 = off, 255 = max).
    @param   green  8-bit green brightnesss (0 = off, 255 = max).
    @param   blue   8-bit blue brightnesss (0 = off, 255 = max).
    @return  'Packed' 16-bit color value (565 format).
*/
uint16_t Adafruit_SPITFT::color565(uint8_t red, uint8_t green, uint8_t blue) {
  return ((red & 0xF8) << 8) | ((green & 0xFC) << 3) | (blue >> 3);
}

The arguments are individual 8-bit R, G, B.
You would extract each 8-bit field from your 24-bit "6-digit hex"

Adafruit_SPITFT class gets built whenever you inherit from Adafruit_GFX.

Most third party libraries will inherit graphics from Adafruit_GFX. But they will probably avoid the mash-up that is Adafruit_SPITFT. Hence they include their own color565(r, g, b) method.

David.

7

Ok, thank you for the information.

8

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