#include <px4_platform_common/px4_config.h>
#include <fcntl.h>
#include <unistd.h>
#include <termios.h>
#include <string.h>
#include "sbus.h"
#include "common_rc.h"
#include <drivers/drv_hrt.h>

Include dependency graph for sbus.cpp:

Classes
struct	sbus_bit_pick

Macros
#define	SBUS_DEBUG_LEVEL 0 /* Set debug output level */

#define	SBUS_START_SYMBOL 0x0f

#define	SBUS_INPUT_CHANNELS 16

#define	SBUS_FLAGS_BYTE 23

#define	SBUS_FAILSAFE_BIT 3

#define	SBUS_FRAMELOST_BIT 2

#define	SBUS1_MAX_RATE_HZ 300

#define	SBUS1_MIN_RATE_HZ 50

#define	SBUS1_DEFAULT_RATE_HZ 72

#define	SBUS_RANGE_MIN 200.0f

#define	SBUS_RANGE_MAX 1800.0f

#define	SBUS_TARGET_MIN 1000.0f

#define	SBUS_TARGET_MAX 2000.0f

#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))

#define	SBUS2_FRAME_SIZE_RX_VOLTAGE 3

#define	SBUS2_FRAME_SIZE_GPS_DIGIT 3

Enumerations
enum	SBUS2_DECODE_STATE { SBUS2_DECODE_STATE_DESYNC = 0xFFF, SBUS2_DECODE_STATE_SBUS_START = 0x2FF, SBUS2_DECODE_STATE_SBUS1_SYNC = 0x00, SBUS2_DECODE_STATE_SBUS2_SYNC = 0x1FF, SBUS2_DECODE_STATE_SBUS2_RX_VOLTAGE = 0x04, SBUS2_DECODE_STATE_SBUS2_GPS = 0x14, SBUS2_DECODE_STATE_SBUS2_DATA1 = 0x24, SBUS2_DECODE_STATE_SBUS2_DATA2 = 0x34 }

Functions
unsigned	sbus_dropped_frames ()
	The number of incomplete frames we encountered. More...

static bool	sbus_decode (uint64_t frame_time, uint8_t frame, uint16_t values, uint16_t num_values, bool sbus_failsafe, bool *sbus_frame_drop, uint16_t max_values)

int	sbus_init (const char *device, bool singlewire)

int	sbus_config (int sbus_fd, bool singlewire)
	Parse serial bytes on the S.BUS bus. More...

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

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

bool	sbus_input (int sbus_fd, uint16_t values, uint16_t num_values, bool sbus_failsafe, bool sbus_frame_drop, uint16_t max_channels)

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)

void	sbus1_set_output_rate_hz (uint16_t rate_hz)

Variables
static hrt_abstime	last_rx_time

static hrt_abstime	last_txframe_time = 0

static enum SBUS2_DECODE_STATE	sbus_decode_state = SBUS2_DECODE_STATE_DESYNC

static sbus_frame_t &	sbus_frame = rc_decode_buf.sbus_frame

static unsigned	partial_frame_count

static unsigned	sbus1_frame_delay = (1000U * 1000U) / SBUS1_DEFAULT_RATE_HZ

static unsigned	sbus_frame_drops

static const struct sbus_bit_pick	sbus_decoder [SBUS_INPUT_CHANNELS][3]

Macro Definition Documentation

◆ SBUS1_DEFAULT_RATE_HZ

#define SBUS1_DEFAULT_RATE_HZ 72

Definition at line 79 of file sbus.cpp.

◆ SBUS1_MAX_RATE_HZ

#define SBUS1_MAX_RATE_HZ 300

Definition at line 75 of file sbus.cpp.

Referenced by sbus1_set_output_rate_hz().

◆ SBUS1_MIN_RATE_HZ

#define SBUS1_MIN_RATE_HZ 50

Definition at line 76 of file sbus.cpp.

Referenced by sbus1_set_output_rate_hz().

◆ SBUS2_FRAME_SIZE_GPS_DIGIT

#define SBUS2_FRAME_SIZE_GPS_DIGIT 3

Definition at line 107 of file sbus.cpp.

◆ SBUS2_FRAME_SIZE_RX_VOLTAGE

#define SBUS2_FRAME_SIZE_RX_VOLTAGE 3

Definition at line 106 of file sbus.cpp.

Referenced by sbus_parse().

◆ SBUS_DEBUG_LEVEL

#define SBUS_DEBUG_LEVEL 0 /* Set debug output level */

Definition at line 57 of file sbus.cpp.

◆ SBUS_FAILSAFE_BIT

#define SBUS_FAILSAFE_BIT 3

Definition at line 68 of file sbus.cpp.

Referenced by sbus_decode().

◆ SBUS_FLAGS_BYTE

#define SBUS_FLAGS_BYTE 23

Definition at line 67 of file sbus.cpp.

Referenced by sbus_decode().

◆ SBUS_FRAMELOST_BIT

#define SBUS_FRAMELOST_BIT 2

Definition at line 69 of file sbus.cpp.

Referenced by sbus_decode().

◆ SBUS_INPUT_CHANNELS

#define SBUS_INPUT_CHANNELS 16

Definition at line 66 of file sbus.cpp.

Referenced by sbus_decode().

◆ SBUS_RANGE_MAX

#define SBUS_RANGE_MAX 1800.0f

Definition at line 90 of file sbus.cpp.

◆ SBUS_RANGE_MIN

#define SBUS_RANGE_MIN 200.0f

Definition at line 89 of file sbus.cpp.

◆ SBUS_SCALE_FACTOR

#define SBUS_SCALE_FACTOR ((SBUS_TARGET_MAX - SBUS_TARGET_MIN) / (SBUS_RANGE_MAX - SBUS_RANGE_MIN))

Definition at line 100 of file sbus.cpp.

Referenced by sbus1_output(), and sbus_decode().

◆ SBUS_SCALE_OFFSET

#define SBUS_SCALE_OFFSET (int)(SBUS_TARGET_MIN - (SBUS_SCALE_FACTOR * SBUS_RANGE_MIN + 0.5f))

Definition at line 101 of file sbus.cpp.

Referenced by sbus1_output(), and sbus_decode().

◆ SBUS_START_SYMBOL

#define SBUS_START_SYMBOL 0x0f

Definition at line 64 of file sbus.cpp.

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

◆ SBUS_TARGET_MAX

#define SBUS_TARGET_MAX 2000.0f

Definition at line 93 of file sbus.cpp.

◆ SBUS_TARGET_MIN

#define SBUS_TARGET_MIN 1000.0f

Definition at line 92 of file sbus.cpp.

Enumeration Type Documentation

◆ SBUS2_DECODE_STATE

enum SBUS2_DECODE_STATE

Enumerator
SBUS2_DECODE_STATE_DESYNC
SBUS2_DECODE_STATE_SBUS_START
SBUS2_DECODE_STATE_SBUS1_SYNC
SBUS2_DECODE_STATE_SBUS2_SYNC
SBUS2_DECODE_STATE_SBUS2_RX_VOLTAGE
SBUS2_DECODE_STATE_SBUS2_GPS
SBUS2_DECODE_STATE_SBUS2_DATA1
SBUS2_DECODE_STATE_SBUS2_DATA2

Definition at line 109 of file sbus.cpp.

Function Documentation

◆ sbus1_output()

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()

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()

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()

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_decode()

bool sbus_decode	(	uint64_t	frame_time,
		uint8_t *	frame,
		uint16_t *	values,
		uint16_t *	num_values,
		bool *	sbus_failsafe,
		bool *	sbus_frame_drop,
		uint16_t	max_values
	)

static

Definition at line 584 of file sbus.cpp.

References sbus_bit_pick::byte, decode(), f(), sbus_bit_pick::lshift, sbus_bit_pick::mask, sbus_bit_pick::rshift, 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, sbus_decode_state, SBUS_FAILSAFE_BIT, SBUS_FLAGS_BYTE, sbus_frame_drops, SBUS_FRAME_SIZE, SBUS_FRAMELOST_BIT, SBUS_INPUT_CHANNELS, SBUS_SCALE_FACTOR, SBUS_SCALE_OFFSET, and SBUS_START_SYMBOL.

Referenced by sbus_dropped_frames(), and sbus_parse().

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◆ sbus_dropped_frames()

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()

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()

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()

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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Variable Documentation

◆ last_rx_time

hrt_abstime last_rx_time

static

Definition at line 103 of file sbus.cpp.

Referenced by sbus_config(), sbus_input(), and sbus_parse().

◆ last_txframe_time

hrt_abstime last_txframe_time = 0

static

Definition at line 104 of file sbus.cpp.

Referenced by sbus1_output().

◆ partial_frame_count

unsigned partial_frame_count

static

Definition at line 122 of file sbus.cpp.

Referenced by sbus_config(), sbus_input(), and sbus_parse().

◆ sbus1_frame_delay

unsigned sbus1_frame_delay = (1000U * 1000U) / SBUS1_DEFAULT_RATE_HZ

static

Definition at line 123 of file sbus.cpp.

Referenced by sbus1_output(), and sbus1_set_output_rate_hz().

◆ sbus_decode_state

enum SBUS2_DECODE_STATE sbus_decode_state = SBUS2_DECODE_STATE_DESYNC

static

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

◆ sbus_decoder

const struct sbus_bit_pick sbus_decoder[SBUS_INPUT_CHANNELS][3]

static

Initial value:

= {
     { { 0, 0, 0xff, 0}, { 1, 0, 0x07, 8}, { 0, 0, 0x00,  0} },
     { { 1, 3, 0x1f, 0}, { 2, 0, 0x3f, 5}, { 0, 0, 0x00,  0} },
     { { 2, 6, 0x03, 0}, { 3, 0, 0xff, 2}, { 4, 0, 0x01, 10} },
     { { 4, 1, 0x7f, 0}, { 5, 0, 0x0f, 7}, { 0, 0, 0x00,  0} },
     { { 5, 4, 0x0f, 0}, { 6, 0, 0x7f, 4}, { 0, 0, 0x00,  0} },
     { { 6, 7, 0x01, 0}, { 7, 0, 0xff, 1}, { 8, 0, 0x03,  9} },
     { { 8, 2, 0x3f, 0}, { 9, 0, 0x1f, 6}, { 0, 0, 0x00,  0} },
     { { 9, 5, 0x07, 0}, {10, 0, 0xff, 3}, { 0, 0, 0x00,  0} },
     { {11, 0, 0xff, 0}, {12, 0, 0x07, 8}, { 0, 0, 0x00,  0} },
     { {12, 3, 0x1f, 0}, {13, 0, 0x3f, 5}, { 0, 0, 0x00,  0} },
     { {13, 6, 0x03, 0}, {14, 0, 0xff, 2}, {15, 0, 0x01, 10} },
     { {15, 1, 0x7f, 0}, {16, 0, 0x0f, 7}, { 0, 0, 0x00,  0} },
     { {16, 4, 0x0f, 0}, {17, 0, 0x7f, 4}, { 0, 0, 0x00,  0} },
     { {17, 7, 0x01, 0}, {18, 0, 0xff, 1}, {19, 0, 0x03,  9} },
     { {19, 2, 0x3f, 0}, {20, 0, 0x1f, 6}, { 0, 0, 0x00,  0} },
     { {20, 5, 0x07, 0}, {21, 0, 0xff, 3}, { 0, 0, 0x00,  0} }
}

Definition at line 564 of file sbus.cpp.

◆ sbus_frame

sbus_frame_t& sbus_frame = rc_decode_buf.sbus_frame

static

Definition at line 120 of file sbus.cpp.

Referenced by sbus_parse().

◆ sbus_frame_drops

unsigned sbus_frame_drops

static

Definition at line 125 of file sbus.cpp.

Referenced by RCTest::sbus2Test(), sbus_config(), sbus_decode(), sbus_dropped_frames(), sbus_input(), and sbus_parse().

Classes

Macros

Enumerations

Functions

Variables

Macro Definition Documentation

◆ SBUS1_DEFAULT_RATE_HZ

◆ SBUS1_MAX_RATE_HZ

◆ SBUS1_MIN_RATE_HZ

◆ SBUS2_FRAME_SIZE_GPS_DIGIT

◆ SBUS2_FRAME_SIZE_RX_VOLTAGE

◆ SBUS_DEBUG_LEVEL

◆ SBUS_FAILSAFE_BIT

◆ SBUS_FLAGS_BYTE

◆ SBUS_FRAMELOST_BIT

◆ SBUS_INPUT_CHANNELS

◆ SBUS_RANGE_MAX

◆ SBUS_RANGE_MIN

◆ SBUS_SCALE_FACTOR

◆ SBUS_SCALE_OFFSET

◆ SBUS_START_SYMBOL

◆ SBUS_TARGET_MAX

◆ SBUS_TARGET_MIN

Enumeration Type Documentation

◆ SBUS2_DECODE_STATE

Function Documentation

◆ sbus1_output()

◆ sbus1_set_output_rate_hz()

◆ sbus2_output()

◆ sbus_config()

◆ sbus_decode()

◆ sbus_dropped_frames()

◆ sbus_init()

◆ sbus_input()

◆ sbus_parse()

Variable Documentation

◆ last_rx_time

◆ last_txframe_time

◆ partial_frame_count

◆ sbus1_frame_delay

◆ sbus_decode_state

◆ sbus_decoder

◆ sbus_frame

◆ sbus_frame_drops