*
*/
+#include <math.h>
+
#include <aversive.h>
#include <aversive/wait.h>
#define BEACON_ID_SHIFT 0
/* */
-#define FRAME_DATA_MASK 0xFFF8
+#define FRAME_DATA_MASK 0x0FF8
#define FRAME_DATA_SHIFT 3
#if (defined MODUL_455KHZ)
#error "no freq defined"
#endif
+#define MIN_DIST 150.
+#define MAX_DIST 3600.
+#define LASER_DIST 25.
+
#define N_CYCLES_PERIOD (N_CYCLES_0 + N_CYCLES_1)
#define LED_PORT PORTD
}
#ifdef WAIT_LASER
-/* get the frame from laser time difference */
+/* val is 12 bits. Return the 16 bits value that includes the 4 bits
+ * cksum in MSB. */
+static uint16_t do_cksum(uint16_t val)
+{
+ uint16_t x, cksum;
+
+ x = (val & 0xfff);
+ /* add the three 4-bits blocks of x together */
+ cksum = x & 0xf;
+ x = x >> 4;
+ cksum += x & 0xf;
+ cksum = (cksum & 0xf) + ((cksum & 0xf0) >> 4);
+ x = x >> 4;
+ cksum += x & 0xf;
+ cksum = (cksum & 0xf) + ((cksum & 0xf0) >> 4);
+ cksum = (~cksum) & 0xf;
+ return (cksum << 12) + (val & 0xfff);
+}
+
+/* get the frame from laser time difference, return 0 on error (this
+ * frame cannot be sent). */
static uint32_t get_frame(uint16_t laserdiff)
{
uint32_t frame = 0;
+ double a, d;
+ uint16_t frame_dist;
+
frame |= ((uint32_t)BEACON_ID << BEACON_ID_SHIFT);
- frame |= ((uint32_t)(laserdiff & FRAME_DATA_MASK) << FRAME_DATA_SHIFT);
- return frame;
+
+ /* process angle from laserdiff time */
+#ifdef SPEED_10RPS
+ /* timer = 2Mhz */
+ a = ((double)laserdiff / (2000000./10.)) * 2. * M_PI;
+#else
+ /* timer = 16Mhz */
+ a = ((double)laserdiff / (16000000./40.)) * 2. * M_PI;
+#endif
+ /* get distance from angle */
+ d = LASER_DIST / sin(a/2);
+
+ /* scale it between 0 and 511 */
+ if (d <= MIN_DIST)
+ return 0;
+ if (d >= MAX_DIST)
+ return 0;
+ d -= MIN_DIST;
+ d /= (MAX_DIST-MIN_DIST);
+ d *= 512;
+ frame_dist = (uint16_t)d;
+ if (frame_dist >= 512) /* should not happen... */
+ return 0;
+
+ frame |= ((uint32_t)(frame_dist & FRAME_DATA_MASK) << FRAME_DATA_SHIFT);
+
+ /* process cksum and return */
+ return do_cksum(frame);
}
/* Wait 2 consecutive rising edges on photodiode. Return 0 on success,
continue;
frame = get_frame(diff);
+ /* cannot convert into frame... skip it */
+ if (frame == 0) {
+ wait_ms(INTER_LASER_TIME);
+ continue;
+ }
/* wait before IR xmit */
while ((int16_t)(when-TCNT1) > 0);