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S.BUS input: Be less sensitive on timing

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Lorenz Meier
2015-11-29 14:55:03 +01:00
parent 6cc1bb7ec8
commit 151402748e
2 changed files with 20 additions and 3 deletions
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src/lib/rc/sbus.c
+2 -3
View File
@@ -174,8 +174,7 @@ sbus_input(int sbus_fd, uint16_t *values, uint16_t *num_values, bool *sbus_fails
* The minimum frame spacing is 7ms; with 25 bytes at 100000bps
* frame transmission time is ~2ms.
*
* We expect to only be called when bytes arrive for processing,
* and if an interval of more than 3ms passes between calls,
* If an interval of more than 4ms passes between calls,
* the first byte we read will be the first byte of a frame.
*
* In the case where byte(s) are dropped from a frame, this also
@@ -184,7 +183,7 @@ sbus_input(int sbus_fd, uint16_t *values, uint16_t *num_values, bool *sbus_fails
*/
now = hrt_absolute_time();
if ((now - last_rx_time) > 3000) {
if ((now - last_rx_time) > 4000) {
if (partial_frame_count > 0) {
sbus_frame_drops++;
partial_frame_count = 0;
src/lib/rc/sbus.h
+18
View File
@@ -47,6 +47,24 @@
__BEGIN_DECLS
__EXPORT int sbus_init(const char *device, bool singlewire);
/**
* Parse serial bytes on the S.BUS bus
*
* 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
* frame transmission time is ~2ms.
*
* If an interval of more than 4ms (7 ms frame spacing plus margin)
* passes between calls, the first byte we read will be the first
* byte of a frame.
*
* In the case where byte(s) are dropped from a frame, this also
* provides a degree of protection. Of course, it would be better
* if we didn't drop bytes...
*/
__EXPORT bool sbus_input(int sbus_fd, uint16_t *values, uint16_t *num_values, bool *sbus_failsafe,
bool *sbus_frame_drop,
uint16_t max_channels);