static void ioinit (void) {
...
	/* timer 1 */
//	TCCR1A = 0;
	TCCR1B = _BV(WGM12) | _BV(CS11); /* 2 MHz */
//	TCCR1C = 0;
	OCR1A = 2000; /* 1 ms */
	TIMSK1 |= _BV(TOIE1);
}


ISR(TIMER1_OVF_vect, ISR_NOBLOCK) {
	uint8_t i;
	for (i=0; i<4; i++) {
		drv8874_set_pwm(i, 0);
	}
}