sbus.h File Reference

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

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

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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. More...

Detailed Description

RC protocol definition for S.BUS.

Author

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

Definition in file sbus.h.

Macro Definition Documentation

SBUS_BUFFER_SIZE

#define SBUS_BUFFER_SIZE   (SBUS_FRAME_SIZE + SBUS_FRAME_SIZE / 2)

Definition at line 50 of file sbus.h.

Referenced by RCInput::cycle(), and RCTest::sbus2Test().

SBUS_FRAME_SIZE

#define SBUS_FRAME_SIZE   25

Definition at line 49 of file sbus.h.

Referenced by sbus1_output(), sbus_decode(), sbus_input(), and sbus_parse().

Typedef Documentation

sbus_frame_t

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

Definition at line 52 of file sbus.h.

Function Documentation

sbus1_output()

__EXPORT void sbus1_output	(	int	sbus_fd,
		uint16_t *	values,
		uint16_t	num_values
	)

Definition at line 237 of file sbus.cpp.

References f(), hrt_absolute_time(), hrt_abstime, last_txframe_time, sbus1_frame_delay, SBUS_FRAME_SIZE, SBUS_SCALE_FACTOR, SBUS_SCALE_OFFSET, and write().

Referenced by mixer_tick(), and sbus2_output().

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sbus1_set_output_rate_hz()

__EXPORT void sbus1_set_output_rate_hz

(

uint16_t

rate_hz

)

Definition at line 705 of file sbus.cpp.

References sbus1_frame_delay, SBUS1_MAX_RATE_HZ, and SBUS1_MIN_RATE_HZ.

Referenced by registers_set_one().

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sbus2_output()

__EXPORT void sbus2_output	(	int	sbus_fd,
		uint16_t *	values,
		uint16_t	num_values
	)

Definition at line 276 of file sbus.cpp.

References sbus1_output().

Referenced by mixer_tick().

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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...

Definition at line 153 of file sbus.cpp.

References hrt_absolute_time(), last_rx_time, partial_frame_count, and sbus_frame_drops.

Referenced by RCInput::cycle(), RCInput::init(), and sbus_init().

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sbus_dropped_frames()

__EXPORT unsigned sbus_dropped_frames

(

void

)

The number of incomplete frames we encountered.

Definition at line 128 of file sbus.cpp.

References sbus_decode(), and sbus_frame_drops.

Referenced by RCInput::print_status().

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sbus_init()

__EXPORT int sbus_init	(	const char *	device,
		bool	singlewire
	)

Definition at line 138 of file sbus.cpp.

References sbus_config().

Referenced by controls_init().

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sbus_input()

__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
	)

Definition at line 282 of file sbus.cpp.

References hrt_absolute_time(), hrt_abstime, last_rx_time, partial_frame_count, read(), SBUS2_DECODE_STATE_DESYNC, sbus_decode_state, sbus_frame_drops, SBUS_FRAME_SIZE, sbus_parse(), and SBUS_START_SYMBOL.

Referenced by controls_tick().

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sbus_parse()

__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
	)

Definition at line 343 of file sbus.cpp.

References last_rx_time, partial_frame_count, SBUS2_DECODE_STATE_DESYNC, SBUS2_DECODE_STATE_SBUS1_SYNC, SBUS2_DECODE_STATE_SBUS2_GPS, SBUS2_DECODE_STATE_SBUS2_RX_VOLTAGE, SBUS2_DECODE_STATE_SBUS2_SYNC, SBUS2_DECODE_STATE_SBUS_START, SBUS2_FRAME_SIZE_RX_VOLTAGE, sbus_decode(), sbus_decode_state, sbus_frame, sbus_frame_drops, SBUS_FRAME_SIZE, and SBUS_START_SYMBOL.

Referenced by RCInput::cycle(), RCTest::sbus2Test(), and sbus_input().

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