Bit-banged ws2801 arduino driver

ws2801.c

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// Data and clock pin locations on the arduino
#define DATA  20
#define CLOCK 21
#define NUM_LED_TOTAL 128

// Each LED has three parameters that determine color and brightness
typedef struct
{
    uint8_t r;
    uint8_t g;
    uint8_t b;
} Led;

// In memory, we'll represent the state of all LEDs as an array of colors
Led led_buf[NUM_LED_TOTAL];

// Initialize the pins used to control the WS2801 driver
void StripInit(void)
{
    pinMode(DATA,OUTPUT);
    pinMode(CLOCK,OUTPUT);
    digitalWrite(DATA,LOW);
    digitalWrite(CLOCK,LOW);
}

// Toggle the clock 8 times and clock out the bit for the color we're sending
inline void StripSend(uint8_t b)
{
    #define _BIT(x) (1<<(x))
    for(int i = 7;i >= 0;i--)
    {
        digitalWrite(CLOCK,LOW);
        digitalWrite(DATA,(b & _BIT(i)));
        digitalWrite(CLOCK,HIGH);
    }
    digitalWrite(CLOCK,LOW);
}

// Clock our the blue-green-red colors and then latch the colors
void StripRefresh(void)
{
    for (int i = 0; i < NUM_LED_TOTAL;i++)
    {
        StripSend(led_buf[i].b);
        StripSend(led_buf[i].g);
        StripSend(led_buf[i].r);
    }
    // WS2801 spec says hold the line for > 500 microseconds to latch colors
    delayMicroseconds(501);
}

// The following function prototypes are required to suppress an error related to
// the "Led" type, defined above.

// Given an LED number and a color save it to the LED array
void StripSetColor(uint16_t n, Led l);
void StripSetColor(uint16_t n, Led l)
{
    led_buf[n] = l;
}

// Given a color defined by r/g/b, return an Led type with those values
Led ColorRGB(uint8_t r, uint8_t g, uint8_t b);
Led ColorRGB(uint8_t r, uint8_t g, uint8_t b)
{
    Led l;
    l.r = r;
    l.g = g;
    l.b = b;
    return l;
}

// Given an LED and a brightness, change each colors in the same proportional
// to change the brightness
Led BrightnessAdjust(Led l, uint8_t brightness);
Led BrightnessAdjust(Led l, uint8_t brightness)
{
    l.r = (l.r * brightness) / 100;
    l.g = (l.g * brightness) / 100;
    l.b = (l.b * brightness) / 100;
    return l;
}

// Given a number between 0-1023, set a color on the spectrum from red-blue
// Useful for driving the strip directly from a 10-bit ADC value.
Led ColorCalculate(uint16_t n);
Led ColorCalculate(uint16_t n)
{
    Led new_color = {0,0,0};
    // red
    if (n >= 0 && n < 511)
    {
        new_color.r = (255 - (n / 2));
    }
    
    // green
    if (n > 0 && n <= 511)
    {
        new_color.g = n / 2;
    }
    else if (n > 511 && n <= 1024)
    {
        new_color.g = (511 - (n / 2));
    }
    
    // blue
    if (n >= 511 && n < 1023)
    {
        new_color.b = ((n / 2) - 255);
    }
    else if (n >= 1023)
    {
        new_color.b = 255;
    }
    return new_color;
}