/* p5_8.c using TC4 Compare Waveform Output
 *
 * This program uses TC4 to generate periodic waveform outputs.
 * The GCLK_TC4 is running at 1 MHz. Prescaler is not used so
 * the timer counter clock is 1 MHz as well.
 * TC4 is set up to run 16-bit Match Frequency mode, in
 * which the counter keeps counting but the output toggles
 * when the counter matches one of the CC register content.
 * The counter counts up and wraps around to 0 when the counter
 * value matches CC0.
 * CC0 is set to 5,000-1 which gives the output of channel 0
 * 1,000,000 / 5,000 / 2 = 100 Hz. (Each period has two toggles.)
 * CC1 is set to half of the value of CC0 so that the outputs of
 * channel 0 and channel 1 have a 90 degree phase.
 * PB12 is used for TC4/WO[0] and PB13 is used for TC4/WO[1].
 *
 * Tested with Atmel Studio 7 v7.0.1006 and Keil MDK-ARM v5.21a.
 */

#include "samd21.h"

unsigned char* ARRAY_PORT_PINCFG1 = (unsigned char*)&REG_PORT_PINCFG1;
unsigned char* ARRAY_PORT_PMUX1 = (unsigned char*)&REG_PORT_PMUX1;

int main (void) {
    REG_GCLK_CLKCTRL = 0x401C;      /* GCLK0 -> TC4/TC5 */
    REG_PM_APBCMASK |= 0x00001000;  /* Enable TC4 Clock in PM */
    REG_TC4_CTRLA = 1;              /* Software Reset */
    while (REG_TC4_CTRLA & 1) {}    /* wait till out of reset */
    REG_TC4_CTRLA = 0x0020;         /* no prescaler, 16-bit mode, MFRQ */
    REG_TC4_COUNT16_CC0 = 5000 - 1; /* match value 0 */
    REG_TC4_COUNT16_CC1 = 2500 - 1; /* match value 1 */
    REG_TC4_CTRLA |= 2;             /* enable */

    ARRAY_PORT_PINCFG1[12] |= 1;    /* make PB12, PB13 output for TC4 */
    ARRAY_PORT_PINCFG1[13] |= 1;
    ARRAY_PORT_PMUX1[6] = 0x44;     /* PB12 = TC4, PB13 = TC4*/
        
    while(1) {
    }
}