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telescience: correctly calculating rate values with higher resolution
author
Robert Garbee
<robert@gag.com>
Thu, 19 Jul 2012 00:41:00 +0000
(18:41 -0600)
committer
Keith Packard
<keithp@keithp.com>
Wed, 17 Oct 2012 05:16:38 +0000
(22:16 -0700)
src/avr/ao_pwmin.c
patch
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diff --git
a/src/avr/ao_pwmin.c
b/src/avr/ao_pwmin.c
index 73a153b2e4cc67332b879e18b02febe1333687c5..84397357a7ee89ee4967b3300f0e2b49950cb62f 100644
(file)
--- a/
src/avr/ao_pwmin.c
+++ b/
src/avr/ao_pwmin.c
@@
-25,20
+25,40
@@
* project payload developed at Challenger Middle School.
*/
* project payload developed at Challenger Middle School.
*/
-volatile __data uint16_t ao_icp3_count;
+volatile __data uint16_t ao_icp3_count = 0;
+volatile __data uint16_t ao_icp3_last = 0;
+
+uint16_t ao_icp3(void)
+{
+ uint16_t v;
+ ao_arch_critical(
+ v = ao_icp3_count;
+ );
+ return v;
+}
static void
ao_pwmin_display(void) __reentrant
{
/* display the most recent value */
static void
ao_pwmin_display(void) __reentrant
{
/* display the most recent value */
- printf("icp 3: %5u\n", ao_icp3
_count
);
+ printf("icp 3: %5u\n", ao_icp3
()
);
}
}
+
+
ISR(TIMER3_CAPT_vect)
{
ISR(TIMER3_CAPT_vect)
{
+
uint8_t lo = ICR3L;
uint8_t hi = ICR3H;
uint8_t lo = ICR3L;
uint8_t hi = ICR3H;
- ao_icp3_count = (hi <<8) | lo;
+ uint16_t ao_icp3_this = (hi <<8) | lo;
+
+ /* handling counter rollovers */
+ if (ao_icp3_this >= ao_icp3_last)
+ ao_icp3_count = ao_icp3_this - ao_icp3_last;
+ else
+ ao_icp3_count = ao_icp3_this + (65536 - ao_icp3_last);
+ ao_icp3_last = ao_icp3_this;
}
__code struct ao_cmds ao_pwmin_cmds[] = {
}
__code struct ao_cmds ao_pwmin_cmds[] = {
@@
-56,7
+76,7
@@
ao_pwmin_init(void)
(0 << ICES3) | /* input capture on falling edge (don't care) */
(0 << WGM33) | /* normal mode, OCR3A */
(0 << WGM32) | /* normal mode, OCR3A */
(0 << ICES3) | /* input capture on falling edge (don't care) */
(0 << WGM33) | /* normal mode, OCR3A */
(0 << WGM32) | /* normal mode, OCR3A */
- (
4 << CS30)); /* clk/256
from prescaler */
+ (
3 << CS30)); /* clk/64
from prescaler */