/* beacon identifier: must be odd, 3 bits */
#define BEACON_ID_MASK 0x7
#define BEACON_ID_SHIFT 0
-#define FRAME_DATA_MASK 0xFFF8
+#define FRAME_DATA_MASK 0xFF8
#define FRAME_DATA_SHIFT 3
/******************* TSOP */
#define FRAME_LEN 16
#define FRAME_MASK ((1UL << FRAME_LEN) - 1)
-/* frame */
-static uint16_t start_angle_time;
-static uint16_t frame;
-static uint16_t mask;
-static uint8_t len;
-static uint8_t val;
-
struct detected_frame {
uint16_t frame;
uint16_t time;
};
+/* frame */
+struct frame_status {
+ uint8_t led_cpt;
+ uint16_t start_angle_time;
+ uint16_t frame;
+ uint16_t mask;
+ uint16_t prev_time;
+ uint8_t prev_tsop;
+ uint8_t len;
+ uint8_t val;
#define FRAME_RING_ORDER 4
#define FRAME_RING_SIZE (1<<FRAME_RING_ORDER)
#define FRAME_RING_MASK (FRAME_RING_SIZE-1)
-static uint8_t frame_ring_head = 0;
-static uint8_t frame_ring_tail = 0;
-static struct detected_frame frame_ring[FRAME_RING_SIZE];
+ uint8_t head;
+ uint8_t tail;
+ struct detected_frame ring[FRAME_RING_SIZE];
+};
+
+static struct frame_status static_beacon;
+
+
/********************** CS */
#endif
}
+/* val is 16 bits, including 4 bits-cksum in MSB, return 0xFFFF is
+ * cksum is wrong, or the 12 bits value on success. */
+static uint16_t verify_cksum(uint16_t val)
+{
+ uint16_t x, cksum;
+
+ x = (val & 0xfff);
+ /* add the four 4-bits blocks of val together */
+ cksum = val & 0xf;
+ val = val >> 4;
+ cksum += val & 0xf;
+ cksum = (cksum & 0xf) + ((cksum & 0xf0) >> 4);
+ val = val >> 4;
+ cksum += val & 0xf;
+ cksum = (cksum & 0xf) + ((cksum & 0xf0) >> 4);
+ val = val >> 4;
+ cksum += val & 0xf;
+ cksum = (cksum & 0xf) + ((cksum & 0xf0) >> 4);
+ if (cksum == 0xf)
+ return x;
+ return 0xffff; /* wrong cksum */
+}
+
+static inline void decode_frame(struct frame_status *status,
+ uint16_t ref_time, uint16_t cur_time, uint8_t cur_tsop)
+{
+ uint16_t diff_time = cur_time - status->prev_time;
+
+ /* first rising edge */
+ if (status->len == 0 && cur_tsop && diff_time > TSOP_TIME_LONG) {
+ status->len = 1;
+ status->val = 1;
+ status->frame = 0;
+ status->start_angle_time = cur_time - ref_time;
+ status->mask = 1;
+ }
+ /* any short edge */
+ else if (status->len != 0 && diff_time < TSOP_TIME_SHORT) {
+ if (status->len & 1) {
+ if (status->val)
+ status->frame |= status->mask;
+ status->mask <<= 1;
+ }
+ status->len ++;
+ }
+ /* any long edge */
+ else if (status->len != 0 && diff_time < TSOP_TIME_LONG) {
+ status->val = !status->val;
+ if (status->val)
+ status->frame |= status->mask;
+ status->mask <<= 1;
+ status->len += 2;
+ }
+ /* error case, reset */
+ else {
+ status->len = 0;
+ }
+
+ /* end of frame */
+ if (status->len == FRAME_LEN*2) {
+ uint8_t tail_next = (status->tail+1) & FRAME_RING_MASK;
+
+ if (tail_next != status->head) {
+ status->ring[status->tail].frame = (status->frame & FRAME_MASK);
+ status->ring[status->tail].time = status->start_angle_time;
+ status->tail = tail_next;
+ if ((status->led_cpt & 0x7) == 0)
+ LED3_TOGGLE();
+ status->led_cpt ++;
+ }
+ status->len = 0;
+ }
+
+ status->prev_time = cur_time;
+ status->prev_tsop = cur_tsop;
+}
+
/* decode frame */
SIGNAL(SIG_TSOP) {
- static uint8_t led_cpt = 0;
+ static uint8_t running = 0;
/* tsop status */
- static uint8_t prev_tsop = 0;
uint8_t cur_tsop;
-
- /* time */
- static uint16_t prev_time;
uint16_t ref_time;
uint16_t cur_time;
- uint16_t diff_time;
ref_time = ICR3;
cur_time = TCNT3;
cur_tsop = TSOP_READ();
- diff_time = cur_time - prev_time;
+
+ /* avoid interruption stacking */
+ if (running)
+ return;
+ running = 1;
+ sei();
if (cur_tsop)
LED2_ON();
else
LED2_OFF();
- /* first rising edge */
- if (len == 0 && cur_tsop && diff_time > TSOP_TIME_LONG) {
- len = 1;
- val = 1;
- frame = 0;
- start_angle_time = cur_time - ref_time;
- mask = 1;
- }
- /* any short edge */
- else if (len != 0 && diff_time < TSOP_TIME_SHORT) {
- if (len & 1) {
- if (val)
- frame |= mask;
- mask <<= 1;
- }
- len ++;
- }
- /* any long edge */
- else if (len != 0 && diff_time < TSOP_TIME_LONG) {
- val = !val;
- if (val)
- frame |= mask;
- mask <<= 1;
- len += 2;
- }
- /* error case, reset */
- else {
- len = 0;
- }
-
- /* end of frame */
- if (len == FRAME_LEN*2) {
- uint8_t tail_next = (frame_ring_tail+1) & FRAME_RING_MASK;
- if (tail_next != frame_ring_head) {
- frame_ring[frame_ring_tail].frame = (frame & FRAME_MASK);
- frame_ring[frame_ring_tail].time = start_angle_time;
- frame_ring_tail = tail_next;
- }
- if ((led_cpt & 0x7) == 0)
- LED3_TOGGLE();
- led_cpt ++;
- }
+ decode_frame(&static_beacon, ref_time, cur_time, cur_tsop);
- prev_time = cur_time;
- prev_tsop = cur_tsop;
+ running = 0;
}
/* absolute value */
return 2000000000L/diff;
}
+/* process the received frame ring */
+void process_ring(struct frame_status *status)
+{
+ uint8_t head_next;
+ uint32_t frame;
+
+ /* after CS, check if we have a new frame in ring */
+ while (status->head != status->tail) {
+ head_next = (status->head+1) & FRAME_RING_MASK;
+ frame = status->ring[status->head].frame;
+
+ /* display if needed */
+ if (beacon_tsop.debug_frame) {
+ uint8_t beacon_id;
+ uint16_t data;
+
+ /* ignore bad cksum */
+ if (verify_cksum(frame) == 0xFFFF)
+ continue;
+
+ beacon_id = (frame >> BEACON_ID_SHIFT) & BEACON_ID_MASK;
+ data = (frame >> FRAME_DATA_SHIFT) & FRAME_DATA_MASK;
+ printf("ID=%d data=%d time=%d\r\n",
+ beacon_id, data,
+ status->ring[status->head].time);
+ }
+ status->head = head_next;
+ }
+}
+
int main(void)
{
uint16_t prev_cs = 0;
if (cpt < CPT_ICR_MAX)
cpt ++;
- /* after CS, check if we have a new frame in ring */
- if (frame_ring_head != frame_ring_tail) {
- uint8_t head_next;
- uint32_t frame;
- head_next = (frame_ring_head+1) & FRAME_RING_MASK;
- frame = frame_ring[frame_ring_head].frame;
-
- /* display if needed */
- if (beacon_tsop.debug_frame) {
- uint8_t beacon_id;
- uint16_t data;
-
- beacon_id = (frame >> BEACON_ID_SHIFT) & BEACON_ID_MASK;
- data = (frame >> FRAME_DATA_SHIFT) & FRAME_DATA_MASK;
- printf("ID=%d data=%d time=%d\r\n",
- beacon_id, data,
- frame_ring[frame_ring_head].time);
- }
- frame_ring_head = head_next;
- }
-
+ process_ring(&static_beacon);
}
return 0;