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lpd8806led.h
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/*
* lpd8806led.h
*
* Copyright 2012 Christopher De Vries
* This program is distributed under the Artistic License 2.0, a copy of which
* is included in the file LICENSE.txt
*/
#ifndef _lpd8806LED_H
#define _lpd8806LED_H
#include <stdint.h>
#include <linux/types.h>
#include <stdlib.h>
/* This header file contains a bit of information about each function and
* data structure in the library. More information can be found in the
* README.txt file which accompanies this library.
*/
/* The lpd8806_color structure consists of 4 bytes (32 bits) in the order in which
* the p9813 chip expects them (flag byte, followed by blue, green, and red).
* You can modify the colors directly, however the functions write_color and
* write_gamma_color are designed to write to the appropriate data to memory
* with a properly calculated flag byte.
*/
typedef struct _lpd8806_color {
// uint8_t flag;
uint8_t green;
uint8_t red;
uint8_t blue;
} lpd8806_color;
/* The lpd8806_buffer structure is a buffer in which pixel data is stored in
* in memory prior to being written out to the SPI device for transmission
* to the pixels. A buffer can be allocated with the lpd8806_init function and
* deallocated with the lpd8806_free function. The buffer contains a pointer to
* an array of lpd8806_color structures representing the array of colors you will
* send to the leds using the send_buffer function. The "pixels" element of
* this structure points to the array of pixels.
*/
typedef struct _lpd8806_buffer {
int leds; /* number of LEDS */
size_t size; /* size of buffer */
lpd8806_color *buffer; /* pointer to buffer memory */
lpd8806_color *pixels; /* pointer to start of pixels */
} lpd8806_buffer;
/* The lpd8806_init function allocates memory for the pixels in an order that
* allows for efficient transfer by the send_buffer command. The function
* takes two arguments:
*
* lpd8806_buffer *buf - A pointer to a lpd8806_buffer structure.
* int leds - The number of LEDs for which memory is to be allocated.
*
* The function returns 0 if successful or a negative number if it cannot
* allocate sufficient memory.
*/
int lpd8806_init(lpd8806_buffer *buf, int leds);
/* The spi_init function initializes the SPI device for use by the lpd8806
* LED strands. It takes one argument:
*
* int filedes - An open file descriptor to an spidev device.
*
* The function returns a negative number if the initialization fails.
*/
int spi_init(int filedes);
/* The write_color function writes the lpd8806_color structure corresponding to
* a color to a location in memory. Typically this location is part of the
* lpd8806_buffer's allocated memory. The function takes four arguments:
*
* lpd8806_color *p - A pointer to a lpd8806_color structure to write to.
* uint8_t red - The red value between 0 (off) and 255 (full on).
* uint8_t green - The green value between 0 (off) and 255 (full on).
* uint8_t blue - The blue value between 0 (off) and 255 (full on).
*/
void write_color(lpd8806_color *p, uint8_t red, uint8_t green, uint8_t blue);
/* The send_buffer function writes the contents of the lpd8806_buffer structure to
* the spi device. It takes two arguments:
*
* int filedes - The open and initialized file descriptor for the spi device.
* lpd8806_buffer *buf - A pointer to a lpd8806_buffer which will be transferred to spi.
*
* This function returns the number of bytes written if successful or a
* negative number if it fails. This function will always block while writing
* and ensure all data is transferred out to the SPI bus.
*/
int send_buffer(int filedes, lpd8806_buffer *buf);
/* The lpd8806_free function will free memory allocated by the lpd8806_init function.
* It wakes one argument:
*
* lpd8806_buffer *buf - A pointer to a lpd8806_buffer that has been allocated by
* lpd8806_init.
*/
void lpd8806_free(lpd8806_buffer *buf);
/* The set_gamma function creates lookup tables which are used to apply the
* gamma correction in the write_gamma_color function. Separate gamma
* correction factors are chosen for each color. This function must be called
* prior to using the write_gamma_color function. It takes three arguments:
*
* double gamma_red - The gamma correction for the red LEDs.
* double gamma_green - The gamma correction for the green LEDs.
* double gamma_blue - The gamma correction for the blue LEDs.
*
* Values between 2.2 and 3.0 appear to work well.
*/
void set_gamma(double gamma_red, double gamma_green, double gamma_blue);
/* The write_gamma_color function writes a gamma corrected pixel color to a
* lpd8806_pixel structure in memory. It behaves the same way as the write_color
* function except that a gamma correction is applied to each color. It takes
* four arguments:
*
* lpd8806_color *p - A pointer to the location in which to write the pixel data.
* uint8_t red - The red value between 0 (off) and 255 (full on).
* uint8_t green - The green value between 0 (off) and 255 (full on).
* uint8_t blue - The blue value between 0 (off) and 255 (full on).
*/
void write_gamma_color(lpd8806_color *p, uint8_t red, uint8_t green, uint8_t blue);
#endif /*!_lpd8806LED_H*/