#define GROUND_AVG_SHIFT 4
#define GROUND_AVG (1 << GROUND_AVG_SHIFT)
+/* Pressure change (in Pa) to detect boost */
+#define BOOST_DETECT 48 /* 4m at sea level, 4.8m at 2000m */
+
+/* Pressure change (in Pa) to detect landing */
+#define LAND_DETECT 12 /* 1m at sea level, 1.2m at 2000m */
+
static void
ao_compute_height(void)
{
sample_count = 0;
for (;;) {
time += SAMPLE_SLEEP;
- ao_delay_until(time);
if (sample_count == 0)
ao_led_on(AO_LED_BLUE);
+ ao_delay_until(time);
ao_pa_get();
if (sample_count == 0)
ao_led_off(AO_LED_BLUE);
if (pa_diff < 0)
pa_diff = -pa_diff;
- /* about 2 meters at sea level, more if you're higher */
- if (pa_diff > (24 << FILTER_SHIFT))
+ /* Check for a significant pressure change */
+ if (pa_diff > (BOOST_DETECT << FILTER_SHIFT))
break;
if (sample_count < GROUND_AVG * 2) {
- ao_led_off(AO_LED_BLUE);
if (sample_count < GROUND_AVG)
pa_sum += pa;
++sample_count;
if (sample_count == (GROUND_AVG - 1)) {
pa_diff = pa_interval_max - pa_interval_min;
- /* About 1m at sea level */
- if (pa_diff < (12 << FILTER_SHIFT))
+
+ /* Check to see if the pressure is now stable */
+ if (pa_diff < (LAND_DETECT << FILTER_SHIFT))
break;
sample_count = 0;
pa_interval_min = pa_avg;