dsm.h File Reference

RC protocol definition for Spektrum RC. More...

#include <stdint.h>
#include <px4_config.h>
#include <px4_defines.h>

Go to the source code of this file.

Classes
struct	dsm_decode_t

Macros
#define	DSM_FRAME_SIZE   16
	DSM frame size in bytes.
#define	DSM_FRAME_CHANNELS   7
	Max supported DSM channels per frame.
#define	DSM_MAX_CHANNEL_COUNT   18
	Max channel count of any DSM RC.
#define	DSM_BUFFER_SIZE   (DSM_FRAME_SIZE + DSM_FRAME_SIZE / 2)
#define	DSM2_BIND_PULSES   3 /* DSM_BIND_START parameter, pulses required to start dsm2 pairing */
#define	DSMX_BIND_PULSES   7 /* DSM_BIND_START parameter, pulses required to start dsmx pairing */
#define	DSMX8_BIND_PULSES   9 /* DSM_BIND_START parameter, pulses required to start 8 or more channel dsmx pairing */

Typedefs
typedef uint8_t	dsm_frame_t[DSM_BUFFER_SIZE]
	DSM dsm frame receive buffer.
typedef uint8_t	dsm_buf_t[DSM_FRAME_SIZE *2]
typedef struct dsm_decode_t	dsm_decode_t

Enumerations
enum	DSM_CMD {   DSM_CMD_BIND_POWER_DOWN = 0, DSM_CMD_BIND_POWER_UP, DSM_CMD_BIND_SET_RX_OUT, DSM_CMD_BIND_SEND_PULSES,   DSM_CMD_BIND_REINIT_UART }

Functions
__EXPORT int	dsm_init (const char *device)
	Initialize the DSM receive functionality. More...
__EXPORT void	dsm_deinit (void)
__EXPORT void	dsm_proto_init (void)
__EXPORT int	dsm_config (int dsm_fd)
__EXPORT bool	dsm_input (int dsm_fd, uint16_t *values, uint16_t *num_values, bool *dsm_11_bit, uint8_t *n_bytes, uint8_t **bytes, int8_t *rssi, unsigned max_values)
	Called periodically to check for input data from the DSM UART. More...
__EXPORT bool	dsm_parse (const uint64_t now, const uint8_t *frame, const unsigned len, uint16_t *values, uint16_t *num_values, bool *dsm_11_bit, unsigned *frame_drops, int8_t *rssi_percent, uint16_t max_channels)

Detailed Description

RC protocol definition for Spektrum RC.

Author

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

Function Documentation

dsm_init()

__EXPORT int dsm_init

(

const char *

device

)

Initialize the DSM receive functionality.

Open the UART for receiving DSM frames and configure it appropriately

Parameters

[in]

device

Device name of DSM UART

dsm_input()

__EXPORT bool dsm_input	(	int	fd,
		uint16_t *	values,
		uint16_t *	num_values,
		bool *	dsm_11_bit,
		uint8_t *	n_bytes,
		uint8_t **	bytes,
		int8_t *	rssi,
		unsigned	max_values
	)

Called periodically to check for input data from the DSM UART.

The DSM* protocol doesn't provide any explicit framing, so we detect dsm frame boundaries by the inter-dsm frame delay. The minimum dsm frame spacing is 11ms; with 16 bytes at 115200bps dsm frame transmission time is ~1.4ms. We expect to only be called when bytes arrive for processing, and if an interval of more than 5ms passes between calls, the first byte we read will be the first byte of a dsm frame. In the case where byte(s) are dropped from a dsm frame, this also provides a degree of protection. Of course, it would be better if we didn't drop bytes... Upon receiving a full dsm frame we attempt to decode it.

Parameters

[out]	values	pointer to per channel array of decoded values
[out]	num_values	pointer to number of raw channel values returned, high order bit 0:10 bit data, 1:11 bit data
[out]	n_butes	number of bytes read
[out]	bytes	pointer to the buffer of read bytes
[out]	rssi	value in percent, if supported, or 127

Returns

true=decoded raw channel values updated, false=no update