PX4-Autopilot/src/lib/rc/st24.h

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/**
 * @file st24.h
 *
 * RC protocol definition for Yuneec ST24 transmitter
 *
 * @author Lorenz Meier <lm@inf.ethz.ch>
 */

#define ST24_DATA_LEN_MAX	64

enum {
	ST24_PACKET_TYPE_CHANNELDATA12 = 0,
	ST24_PACKET_TYPE_CHANNELDATA24,
	ST24_PACKET_TYPE_TRANSMITTERGPSDATA
} ST24_PACKET_TYPE;

#pragma pack(push, 1)
typedef struct {
	uint8_t	header1;				///< 0x55 for a valid packet
	uint8_t	header2;				///< 0x55 for a valid packet
	uint8_t	length;				///< length includes type, data, and crc = sizeof(type)+sizeof(data[payload_len])+sizeof(crc8)
	uint8_t	type;					///< from enum ST24_PACKET_TYPE
	uint8_t	st24_data[ST24_DATA_LEN_MAX];
	uint8_t	crc8;					///< crc8 checksum, calculated by st24_common_crc8 and including fields length, type and st24_data
} ReceiverFcPacket;

/**
 * RC Channel data (12 channels).
 *
 * This is incoming from the ST24
 */
typedef struct {
	uint16_t	t;						///< packet counter or clock
	uint8_t	rssi					///< signal strength
	uint8_t	packet_count;		///< Number of UART packets sent since reception of last RF frame (this tells something about age / rate)
	uint8_t	channel[18];		///< channel data, 12 channels (12 bit numbers)
} ChannelData12;

/**
 * RC Channel data (12 channels).
 *
 */
typedef struct {
	uint16_t	t;						///< packet counter or clock
	uint8_t	rssi					///< signal strength
	uint8_t	packet_count;		///< Number of UART packets sent since reception of last RF frame (this tells something about age / rate)
	uint8_t	channel[36];		///< channel data, 24 channels (12 bit numbers)
} ChannelData24;

/**
 * Telemetry packet
 *
 * This is outgoing to the ST24
 *
 * imuStatus:
 * 8 bit total
 * bits 0-2 for status
 * - value 0 is FAILED
 * - value 1 is INITIALIZING
 * - value 2 is RUNNING
 * - values 3 through 7 are reserved
 * bits 3-7 are status for sensors (0 or 1)
 * - mpu6050
 * - accelerometer
 * - primary gyro x
 * - primary gyro y
 * - primary gyro z
 *
 * pressCompassStatus
 * 8 bit total
 * bits 0-3 for compass status
 * - value 0 is FAILED
 * - value 1 is INITIALIZING
 * - value 2 is RUNNING
 * - value 3 - 15 are reserved
 * bits 4-7 for pressure status
 * - value 0 is FAILED
 * - value 1 is INITIALIZING
 * - value 2 is RUNNING
 * - value 3 - 15 are reserved
 *
 */
typedef struct {
	uint16_t t;						///< packet counter or clock
	int32_t	lat;					///< lattitude (degrees)	+/- 90 deg
	int32_t	lon;					///< longitude (degrees)	+/- 180 deg
	int32_t	alt;					///< 0.01m resolution, altitude (meters)
	int16_t	vx, vy, vz; 		///< velocity 0.01m res, +/-320.00 North-East- Down
	uint8_t	nsat;					///<number of satellites
	uint8_t	voltage; 			///< 25.4V	voltage = 5 + 255*0.1 = 30.5V, min=5V
	uint8_t	current; 			///< 0.5A resolution
	int16_t	roll, pitch, yaw;	///< 0.01 degree resolution
	uint8_t	motorStatus;		///< 1 bit per motor for status 1=good, 0= fail
	uint8_t	imuStatus;			///< inertial measurement unit status
	uint8_t	pressCompassStatus;	///< baro / compass status
} TelemetryData;

#pragma pack(pop)

/**
 * CRC8 implementation for ST24 protocol
 *
 * @param prt Pointer to the data to CRC
 * @param len number of bytes to accumulate in the checksum
 * @return the checksum of these bytes over len
 */
uint8_t st24_common_crc8(uint8_t *ptr, uint8_t len);

/**
 * Decoder for ST24 protocol
 *
 * @param byte current char to read
 * @param rssi pointer to a byte where the RSSI value is written back to
 * @param rx_count pointer to a byte where the receive count of packets signce last wireless frame is written back to
 * @param channels pointer to a datastructure of size max_chan_count where channel values (12 bit) are written back to
 * @param max_chan_count maximum channels to decode - if more channels are decoded, the last n are skipped and success (0) is returned
 * @return 0 for success (a decoded packet), 1 for no packet yet (accumulating), 3 for out of sync, 4 for checksum error
 */
__EXPORT uint8_t st24_decode(uint8_t byte, uint8_t *rssi, uint8_t* rx_count, uint16_t *channels, uint16_t max_chan_count);