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S.BUS parser rewrite to address FrSky timing and S.BUS2 commands

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This commit is contained in:
Lorenz Meier
2015-12-07 11:41:01 +01:00
parent 37f7460fea
commit 990e8acaea
1 changed files with 107 additions and 53 deletions
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src/lib/rc/sbus.c
+107 -53
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@@ -49,13 +49,19 @@
#define SBUS_START_SYMBOL 0x0f
#define SBUS_FRAME_SIZE 25
#define SBUS_MAX_BUF_SIZE (SBUS_FRAME_SIZE + 15)
#define SBUS_INPUT_CHANNELS 16
#define SBUS_FLAGS_BYTE 23
#define SBUS_FAILSAFE_BIT 3
#define SBUS_FRAMELOST_BIT 2
#define SBUS1_FRAME_DELAY 14000
#define SBUS_SINGLE_CHAR_LEN_US ((1/((100000/10)) * 1000 * 1000)
#define SBUS_SINGLE_CHAR_LEN_US (1/((100000/10)) * 1000 * 1000)
#define SBUS_FRAME_INTERVAL_US (SBUS_SINGLE_CHAR_LEN_US * SBUS_FRAME_SIZE)
#define SBUS_FRAME_GAP_US 6200
#define SBUS_MIN_CALL_INTERVAL_US (SBUS_FRAME_GAP_US / 3)
#define SBUS_EPSILON_US 2500
/*
Measured values with Futaba FX-30/R6108SB:
@@ -71,6 +77,15 @@
#define SBUS_TARGET_MIN 1000.0f
#define SBUS_TARGET_MAX 2000.0f
#define SBUS_SYNC_PHASE0 0
#define SBUS_SYNC_PHASE1 1
#define SBUS_DEBUG
#ifdef SBUS_DEBUG
#include <stdio.h>
#endif
/* pre-calculate the floating point stuff as far as possible at compile time */
#define SBUS_SCALE_FACTOR ((SBUS_TARGET_MAX - SBUS_TARGET_MIN) / (SBUS_RANGE_MAX - SBUS_RANGE_MIN))
#define SBUS_SCALE_OFFSET (int)(SBUS_TARGET_MIN - (SBUS_SCALE_FACTOR * SBUS_RANGE_MIN + 0.5f))
@@ -79,11 +94,12 @@ static hrt_abstime last_rx_time;
static hrt_abstime last_frame_time;
static hrt_abstime last_txframe_time = 0;
static uint8_t frame[SBUS_FRAME_SIZE];
static uint8_t frame[SBUS_MAX_BUF_SIZE];
static unsigned partial_frame_count;
unsigned sbus_frame_drops;
static unsigned sbus_frame_drops;
static unsigned sbus_sync = SBUS_SYNC_PHASE0;
unsigned
sbus_dropped_frames()
@@ -174,14 +190,14 @@ bool
sbus_input(int sbus_fd, uint16_t *values, uint16_t *num_values, bool *sbus_failsafe, bool *sbus_frame_drop,
uint16_t max_channels)
{
ssize_t ret;
int ret;
hrt_abstime now;
/*
* The S.bus protocol doesn't provide reliable framing,
* so we detect frame boundaries by the inter-frame delay.
*
* The minimum frame spacing is 7ms; with 25 bytes at 100000bps
* The minimum frame spacing is 6ms; with 25 bytes at 100000bps
* frame transmission time is ~2500 us.
*
* If an interval of more than 2ms passes between calls,
@@ -193,60 +209,76 @@ sbus_input(int sbus_fd, uint16_t *values, uint16_t *num_values, bool *sbus_fails
*/
now = hrt_absolute_time();
/*
* If we timed out, reset the decoder
*/
if ((now - last_rx_time) > 3600) {
if (partial_frame_count > 0) {
sbus_frame_drops++;
if (sbus_sync == SBUS_SYNC_PHASE0) {
/* empty the UART buffer */
int ret = read(sbus_fd, &frame[0], sizeof(frame) / sizeof(frame[0]));
/* establish the last data we got */
if (ret > 0) {
last_rx_time = now;
bool rc_control_packet = false;
for (unsigned i = 0; i < ret; i++) {
if (frame[i] == SBUS_START_SYMBOL) {
rc_control_packet = true;
}
}
if (rc_control_packet) {
/* we should not be reading anything in this state if synced */
sbus_frame_drops++;
}
/* There are two known valid S.BUS 2 commands:
*
* 0x3 0x84 0x0
* 0x3 0x80 0x2f
*/
}
/* wait until a frame gap has passed */
if (now - last_rx_time > (SBUS_FRAME_INTERVAL_US + 500)) {
/* ready to decode - reset buffer and start filling it */
sbus_sync = SBUS_SYNC_PHASE1;
partial_frame_count = 0;
} else {
return false;
}
}
bool decode_success = false;
/*
* Get all data
*/
ret = read(sbus_fd, &frame[partial_frame_count], SBUS_MAX_BUF_SIZE);
do {
/*
* Fetch bytes, but no more than we would need to complete
* the current frame.
*/
ret = read(sbus_fd, &frame[partial_frame_count], SBUS_FRAME_SIZE - partial_frame_count);
/* if the read failed for any reason, just give up here */
if (ret < 1) {
return false;
}
/* if the read failed for any reason, just give up here */
if (ret < 1) {
break;
}
last_rx_time = now;
last_rx_time = now;
/*
* Add bytes to the current frame
*/
partial_frame_count += ret;
/*
* Add bytes to the current frame
*/
partial_frame_count += ret;
/*
* If we don't have a full frame, return
*/
if (partial_frame_count < SBUS_FRAME_SIZE) {
return false;
}
/* if the first byte of the frame is not the start symbol, give up instantly */
if (partial_frame_count > 0 && (frame[0] != SBUS_START_SYMBOL)) {
sbus_frame_drops++;
partial_frame_count = 0;
continue;
}
/*
* If we don't have a full frame, return
*/
if (partial_frame_count < SBUS_FRAME_SIZE) {
continue;
}
/*
* Great, it looks like we might have a frame. Go ahead and
* decode it.
*/
partial_frame_count = 0;
decode_success = decode_success || sbus_decode(now, values, num_values, sbus_failsafe, sbus_frame_drop, max_channels);
} while (ret > 0);
return decode_success;
/*
* Great, it looks like we might have a frame. Go ahead and
* decode it.
*/
return sbus_decode(now, values, num_values, sbus_failsafe, sbus_frame_drop, max_channels);
}
/*
@@ -289,13 +321,33 @@ static bool
sbus_decode(hrt_abstime frame_time, uint16_t *values, uint16_t *num_values, bool *sbus_failsafe, bool *sbus_frame_drop,
uint16_t max_values)
{
/* skip over valid S.BUS 2 command sequences */
unsigned s = 0;
if ((frame[0] == 0x3 && frame[1] == 0x84 && frame[2] == 0x0) ||
(frame[0] == 0x3 && frame[1] == 0xc4 && frame[2] == 0x0) ||
(frame[0] == 0x3 && frame[1] == 0x80 && frame[2] == 0x2f) ||
(frame[0] == 0x3 && frame[1] == 0xc0 && frame[2] == 0x2f)) {
s = 3;
}
/* check frame boundary markers to avoid out-of-sync cases */
if ((frame[0] != SBUS_START_SYMBOL)) {
if ((frame[s + 0] != SBUS_START_SYMBOL)) {
sbus_frame_drops++;
sbus_sync = SBUS_SYNC_PHASE0;
printf("decode fail:");
for (unsigned i = 0; i < SBUS_FRAME_SIZE; i++) {
printf("0x%0x ", frame[i]);
}
printf("\n");
return false;
}
switch (frame[24]) {
switch (frame[s + 24]) {
case 0x00:
/* this is S.BUS 1 */
break;
@@ -335,7 +387,7 @@ sbus_decode(hrt_abstime frame_time, uint16_t *values, uint16_t *num_values, bool
const struct sbus_bit_pick *decode = &sbus_decoder[channel][pick];
if (decode->mask != 0) {
unsigned piece = frame[1 + decode->byte];
unsigned piece = frame[s + 1 + decode->byte];
piece >>= decode->rshift;
piece &= decode->mask;
piece <<= decode->lshift;
@@ -383,5 +435,7 @@ sbus_decode(hrt_abstime frame_time, uint16_t *values, uint16_t *num_values, bool
*sbus_frame_drop = false;
}
sbus_sync = SBUS_SYNC_PHASE0;
return true;
}