MAVLink 2.0

MAVLink协议：

MavLink协议目前网上可以找到的中文版资料只有1.0的。现在开发使用的固件版本号是1.7.3.串口抓的的包全部与1.0版本都不一致。爬到官方去看了下。有2.0的包结构。

uint8_t magic;              ///< protocol magic marker
uint8_t len;                ///< Length of payload
uint8_t incompat_flags;     ///< flags that must be understood
uint8_t compat_flags;       ///< flags that can be ignored if not understood
uint8_t seq;                ///< Sequence of packet
uint8_t sysid;              ///< ID of message sender system/aircraft
uint8_t compid;             ///< ID of the message sender component
uint8_t msgid 0:7;          ///< first 8 bits of the ID of the message
uint8_t msgid 8:15;         ///< middle 8 bits of the ID of the message
uint8_t msgid 16:23;        ///< last 8 bits of the ID of the message
uint8_t target_sysid;       ///< Optional field for point-to-point messages, used for payload else
uint8_t target_compid;      ///< Optional field for point-to-point messages, used for payload else
uint8_t payload[max 253];   ///< A maximum of 253 payload bytes
uint16_t checksum;          ///< X.25 CRC
uint8_t signature[13];      ///< Signature which allows ensuring that the link is tamper-proof

包结构大致如下：

部分	长度	内容
n1 STX	1B	帧头部分，2.0版本为 0xFD
n2 LEN	1B	PLAYLOAD数据长度
n3	1B	incompat_flags
n4	1B	compat_flags
n5 SEQ	1B	消息帧序号
n6 SYS	1B	消息系统编号
n7 COMP	1B	罗盘编号
n8 MSG	3B	msgid,消息标号，MavlinkMessage
n9	1B	target_sysid可选
n10	1B	target_compid可选
n11 PLAYLOAD	2B	消息内容
n12	2B	CRC校验
n13	1B	签名

2.0包的总长为10+n+3(+2),其中括号的2为可选内容。抓包未发现。

抓包获得来自飞控的Msgind如下。

0,36,74,105,30,31,32,140,1,147,65,70,141,230,241,111,83,69,24

這些都是飞控无请求时主动发送过来的数据。

根据msgid：

HEX	DEC	TYPE
00	0	HEARTBEAT
01	1	SYS_STATUS
18	24	GPS_RAW_INT
1E	30	ATTITUDE
1F	31	ATTITUDE_QUATERNION
20	32	LOCAL_POSITION_NED
24	36	SERVO_OUTPUT_RAW
41	65	RC_CHANNELS
45	69	MANUAL_CONTROL
46	70	RC_CHANNELS_OVERRIDE
4A	74	VFR_HUD
53	83	ATTITUDE_TARGET
69	105	HIGHRES_IMU
6F	111	TIMESYNC
8C	140	ACTUATOR_CONTROL_TARGET
8D	141	ALTITUDE
93	147	BATTERY_STATUS
E6	230	ESTIMATOR_STATUS
E7	231	WIND_COV
F1	241	VIBRATION
F5	245	EXTENDED_SYS_STATE