sbus.h File Reference

RC protocol definition for S.BUS. More...

#include <stdint.h>
#include <stdbool.h>

Go to the source code of this file.

Macros
#define	SBUS_FRAME_SIZE   25
#define	SBUS_BUFFER_SIZE   (SBUS_FRAME_SIZE + SBUS_FRAME_SIZE / 2)

Typedefs
typedef uint8_t	sbus_frame_t[SBUS_FRAME_SIZE+(SBUS_FRAME_SIZE/2)]

Functions
__EXPORT int	sbus_init (const char *device, bool singlewire)
__EXPORT int	sbus_config (int sbus_fd, bool singlewire)
	Parse serial bytes on the S.BUS bus. More...
__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)
__EXPORT bool	sbus_parse (uint64_t now, uint8_t *frame, unsigned len, uint16_t *values, uint16_t *num_values, bool *sbus_failsafe, bool *sbus_frame_drop, unsigned *frame_drops, uint16_t max_channels)
__EXPORT void	sbus1_output (int sbus_fd, uint16_t *values, uint16_t num_values)
__EXPORT void	sbus2_output (int sbus_fd, uint16_t *values, uint16_t num_values)
__EXPORT void	sbus1_set_output_rate_hz (uint16_t rate_hz)
__EXPORT unsigned	sbus_dropped_frames (void)
	The number of incomplete frames we encountered.

Detailed Description

RC protocol definition for S.BUS.

Author

Lorenz Meier loren.nosp@m.z@px.nosp@m.4.io

Function Documentation

sbus_config()

__EXPORT int sbus_config	(	int	sbus_fd,
		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...