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scitor/main.c

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Created August 26, 2014 07:43
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  1. @funkfinger funkfinger revised this gist May 4, 2011. 1 changed file with 3 additions and 0 deletions.
    3 changes: 3 additions & 0 deletions main.c
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    Original file line number Diff line number Diff line change
    @@ -1,3 +1,6 @@
    // based largely on Atmel's AVR136: Low-Jitter Multi-Channel Software PWM Application Note:
    // http://www.atmel.com/dyn/resources/prod_documents/doc8020.pdf

    #include <avr/io.h>
    #include <util/delay.h>
    #include <avr/interrupt.h>
  2. @funkfinger funkfinger created this gist May 4, 2011.
    132 changes: 132 additions & 0 deletions main.c
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    @@ -0,0 +1,132 @@
    #include <avr/io.h>
    #include <util/delay.h>
    #include <avr/interrupt.h>

    #define CHMAX 3 // maximum number of PWM channels
    #define PWMDEFAULT 0x00 // default PWM value at start up for all channels

    #define RED_CLEAR (pinlevelB &= ~(1 << RED)) // map RED to PB0
    #define GREEN_CLEAR (pinlevelB &= ~(1 << GREEN)) // map GREEN to PB1
    #define BLUE_CLEAR (pinlevelB &= ~(1 << BLUE)) // map BLUE to PB2

    //! Set bits corresponding to pin usage above
    #define PORTB_MASK (1 << PB0)|(1 << PB1)|(1 << PB2)

    #define set(x) |= (1<<x)
    #define clr(x) &=~(1<<x)
    #define inv(x) ^=(1<<x)

    #define RED PB0
    #define GREEN PB1
    #define BLUE PB2
    #define LED_PORT PORTB
    #define LED_DDR DDRB

    void delay_ms(uint16_t ms);
    void init();

    unsigned char compare[CHMAX];
    volatile unsigned char compbuff[CHMAX];

    int r_val = 0x00;
    int g_val = 0x55;
    int b_val = 0xAA;
    float dim = 1;

    int main() {
    init();

    int r_dir = 1;
    int g_dir = 2;
    int b_dir = 4;

    for(;;) {
    if (r_val > 254 - 1) {
    r_dir = -1;
    }
    if (r_val < 1 + 1) {
    r_dir = 1;
    }

    if (g_val > 254 - 3) {
    g_dir = -2;
    }
    if (g_val < 1 + 3) {
    g_dir = 2;
    }

    if (b_val > 254 - 4) {
    b_dir = -4;
    }
    if (b_val < 1 + 4) {
    b_dir = 4;
    }

    r_val += r_dir;
    g_val += g_dir;
    b_val += b_dir;

    compbuff[0] = r_val;
    compbuff[1] = g_val;
    compbuff[2] = b_val;

    delay_ms(50);
    }
    }


    void delay_ms(uint16_t ms) {
    while (ms) {
    _delay_ms(1);
    ms--;
    }
    }

    void init(void) {
    // set the direction of the ports
    LED_DDR set(RED);
    LED_DDR set(GREEN);
    LED_DDR set(BLUE);

    unsigned char i, pwm;

    CLKPR = (1 << CLKPCE); // enable clock prescaler update
    CLKPR = 0; // set clock to maximum (= crystal)

    pwm = PWMDEFAULT;

    // initialise all channels
    for(i=0 ; i<CHMAX ; i++) {
    compare[i] = pwm; // set default PWM values
    compbuff[i] = pwm; // set default PWM values
    }

    TIFR = (1 << TOV0); // clear interrupt flag
    TIMSK = (1 << TOIE0); // enable overflow interrupt
    TCCR0B = (1 << CS00); // start timer, no prescale

    sei();
    }


    ISR (TIM0_OVF_vect) {
    static unsigned char pinlevelB=PORTB_MASK;
    static unsigned char softcount=0xFF;

    PORTB = pinlevelB; // update outputs

    if(++softcount == 0){ // increment modulo 256 counter and update
    // the compare values only when counter = 0.
    compare[0] = compbuff[0]; // verbose code for speed
    compare[1] = compbuff[1];
    compare[2] = compbuff[2];

    pinlevelB = PORTB_MASK; // set all port pins high
    }
    // clear port pin on compare match (executed on next interrupt)
    if(compare[0] == softcount) RED_CLEAR;
    if(compare[1] == softcount) GREEN_CLEAR;
    if(compare[2] == softcount) BLUE_CLEAR;
    }