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fw/sweep.c: use ICR1 instead of double-buffered OCR1A; set pixel_ticks

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Our timing is now accurate within a measured 0.5% on the test device,
which is well within the specified 1% of the calibrated RC oscillator.
This commit is contained in:
Werner Almesberger 2012-06-20 16:40:33 -03:00
parent 878498a405
commit 6286aa9bbc
1 changed files with 10 additions and 10 deletions
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20
fw/sweep.c
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@ -40,7 +40,7 @@ ISR(TIMER1_OVF_vect)
{ {
/* update the sweep time */ /* update the sweep time */
t_sw += OCR1A; t_sw += ICR1;
/* if at the end of the image, only update the time */ /* if at the end of the image, only update the time */
@ -51,7 +51,7 @@ ISR(TIMER1_OVF_vect)
if (wait_periods) { if (wait_periods) {
if (!--wait_periods) if (!--wait_periods)
OCR1A = wait_short; ICR1 = wait_short;
return; return;
} }
@ -71,10 +71,10 @@ ISR(TIMER1_OVF_vect)
/* wait until the next pixel (or slow down if we're done) */ /* wait until the next pixel (or slow down if we're done) */
if (curr_line == end_line) { if (curr_line == end_line) {
OCR1A = 0xffff; ICR1 = 0xffff;
sweeping = 0; sweeping = 0;
} else { } else {
OCR1A = pixel_ticks; ICR1 = pixel_ticks;
} }
} }
@ -104,22 +104,23 @@ void sweep_image(const struct sweep *sweep)
/* timing parameters */ /* timing parameters */
pixel_ticks = sweep->pixel_ticks;
wait_periods = sweep->wait_ticks >> 16; wait_periods = sweep->wait_ticks >> 16;
if (wait_periods) { if (wait_periods) {
wait_short = sweep->wait_ticks; wait_short = sweep->wait_ticks;
wait_period = 0xffff; wait_period = 0xffff;
/* /*
* Make sure we have plenty of time to update OCR1A after an * Make sure we have plenty of time to update ICR1 after an
* interrupt. * interrupt.
*/ */
if (wait_short < 256) { if (wait_short < 256) {
wait_period -= 128; wait_period -= 128;
wait_short += wait_periods << 7; wait_short += wait_periods << 7;
} }
OCR1A = wait_period; ICR1 = wait_period;
} else { } else {
OCR1A = sweep->wait_ticks; ICR1 = sweep->wait_ticks;
} }
/* prepare the hardware timer */ /* prepare the hardware timer */
@ -131,7 +132,7 @@ void sweep_image(const struct sweep *sweep)
/* start the timer */ /* start the timer */
TCCR1B = TCCR1B =
1 << WGM13 | /* WG Mode 15, continued */ 1 << WGM13 | /* WG Mode 14, continued */
1 << WGM12 | 1 << WGM12 |
1 << CS11; /* clkIO/8 */ 1 << CS11; /* clkIO/8 */
@ -144,8 +145,7 @@ void sweep_image(const struct sweep *sweep)
void sweep_init(void) void sweep_init(void)
{ {
TCCR1A = TCCR1A =
1 << WGM11 | /* WG Mode 15 (Fast PWM to OCR1A) */ 1 << WGM11; /* WG Mode 14 (Fast PWM to ICR1) */
1 << WGM10;
TCNT1 = 0; TCNT1 = 0;