MAVLink源文件结构

MAVLink是为微型飞行器MAV（Micro Air Vehicle）设计的（LGPL）开源的通讯协议。是无人飞行器和地面站（Ground Control Station ，GCS）之间，以及无人飞行器之间通讯常用的协议。APM、PIXHAWK飞控，Mission Planner、QGroundControl地面站均使用了MAVLink协议进行通讯。

common文件夹：原始的MAVLink消息，包括各种消息的头文件
- common.h ：定义MAVLink各个消息包中用到的枚举类型，各个消息包对应的CRC-EXTRA值、LENGTH值，包含（include）各个消息包的头文件
- 各个消息的头文件：
  - 1）定义消息内容对应的数据结构
  - 2）打包、发送消息的便捷函数
  - 3）消息包解析并获取各个参数
autopilotmega，ASLUAV，pixhawk等文件夹：包含各个飞控自定义的MAVLink消息类型
checksum.h：计算校验码的代码
mavlink_conversions.h：dcm，欧拉角，四元数之间的转换
mavlink_helper.h：提供各种便捷函数：
- 将各个消息包补充完整并发送。将数据载荷加上消息帧的头部，如sysid和compid等，计算校验码，补充成为完整的mavlink消息包后发送；
- MAVLink消息包解析。
mavlink_types.h：定义用到的各种基本结构体（如mavlink_message_t）、枚举类型（如
mavlink_param_union_t）

mavlink消息包

　注：校验（checksum）功能。加入MAVLINK_CRC_EXTRA，当两个通讯终端之间（飞行器和地面站，或飞行器和飞行器）使用不同版本的MAVLink协议时，双方计算得到的校验码会不同，则不同版本的MAVLink协议之间将无法通讯。

MAVLINK_MESSAGE_CRCS中存储了每种消息包对应的MAVLINK_CRC_EXTRA。
这个MAVLINK_CRC_EXTRA在用python生成MAVLink代码时在common.h头文件中自动生成。

mavlink解析函数

MAVLINK_HELPER uint8_t mavlink_frame_char_buffer(mavlink_message_t* rxmsg, mavlink_status_t* status,uint8_t c, mavlink_message_t* r_message, mavlink_status_t* r_mavlink_status)
{/* Enable this option to check the length of each message.This allows invalid messages to be caught much sooner. Use if the transmissionmedium is prone to missing (or extra) characters (e.g. a radio that fades inand out). Only use if the channel will only contain messages types listed inthe headers.*/
#ifdef MAVLINK_CHECK_MESSAGE_LENGTH
#ifndef MAVLINK_MESSAGE_LENGTHstatic const uint8_t mavlink_message_lengths[256] = MAVLINK_MESSAGE_LENGTHS;
#define MAVLINK_MESSAGE_LENGTH(msgid) mavlink_message_lengths[msgid]
#endif
#endifint bufferIndex = 0;status->msg_received = MAVLINK_FRAMING_INCOMPLETE;switch (status->parse_state){case MAVLINK_PARSE_STATE_UNINIT:case MAVLINK_PARSE_STATE_IDLE:if (c == MAVLINK_STX){status->parse_state = MAVLINK_PARSE_STATE_GOT_STX;rxmsg->len = 0;rxmsg->magic = c;status->flags &= ~MAVLINK_STATUS_FLAG_IN_MAVLINK1;mavlink_start_checksum(rxmsg);} else if (c == MAVLINK_STX_MAVLINK1){status->parse_state = MAVLINK_PARSE_STATE_GOT_STX;rxmsg->len = 0;rxmsg->magic = c;status->flags |= MAVLINK_STATUS_FLAG_IN_MAVLINK1;mavlink_start_checksum(rxmsg);}break;case MAVLINK_PARSE_STATE_GOT_STX:if (status->msg_received
/* Support shorter buffers than thedefault maximum packet size */
#if (MAVLINK_MAX_PAYLOAD_LEN < 255)|| c > MAVLINK_MAX_PAYLOAD_LEN
#endif){status->buffer_overrun++;_mav_parse_error(status);status->msg_received = 0;status->parse_state = MAVLINK_PARSE_STATE_IDLE;}else{// NOT counting STX, LENGTH, SEQ, SYSID, COMPID, MSGID, CRC1 and CRC2rxmsg->len = c;status->packet_idx = 0;mavlink_update_checksum(rxmsg, c);if (status->flags & MAVLINK_STATUS_FLAG_IN_MAVLINK1) {rxmsg->incompat_flags = 0;rxmsg->compat_flags = 0;status->parse_state = MAVLINK_PARSE_STATE_GOT_COMPAT_FLAGS;} else {status->parse_state = MAVLINK_PARSE_STATE_GOT_LENGTH;}}break;case MAVLINK_PARSE_STATE_GOT_LENGTH:rxmsg->incompat_flags = c;if ((rxmsg->incompat_flags & ~MAVLINK_IFLAG_MASK) != 0) {// message includes an incompatible feature flag_mav_parse_error(status);status->msg_received = 0;status->parse_state = MAVLINK_PARSE_STATE_IDLE;break;}mavlink_update_checksum(rxmsg, c);status->parse_state = MAVLINK_PARSE_STATE_GOT_INCOMPAT_FLAGS;break;case MAVLINK_PARSE_STATE_GOT_INCOMPAT_FLAGS:rxmsg->compat_flags = c;mavlink_update_checksum(rxmsg, c);status->parse_state = MAVLINK_PARSE_STATE_GOT_COMPAT_FLAGS;break;case MAVLINK_PARSE_STATE_GOT_COMPAT_FLAGS:rxmsg->seq = c;mavlink_update_checksum(rxmsg, c);status->parse_state = MAVLINK_PARSE_STATE_GOT_SEQ;break;case MAVLINK_PARSE_STATE_GOT_SEQ:rxmsg->sysid = c;mavlink_update_checksum(rxmsg, c);status->parse_state = MAVLINK_PARSE_STATE_GOT_SYSID;break;case MAVLINK_PARSE_STATE_GOT_SYSID:rxmsg->compid = c;mavlink_update_checksum(rxmsg, c);status->parse_state = MAVLINK_PARSE_STATE_GOT_COMPID;break;case MAVLINK_PARSE_STATE_GOT_COMPID:rxmsg->msgid = c;mavlink_update_checksum(rxmsg, c);if (status->flags & MAVLINK_STATUS_FLAG_IN_MAVLINK1) {if(rxmsg->len > 0){status->parse_state = MAVLINK_PARSE_STATE_GOT_MSGID3;} else {status->parse_state = MAVLINK_PARSE_STATE_GOT_PAYLOAD;}
#ifdef MAVLINK_CHECK_MESSAGE_LENGTHif (rxmsg->len != MAVLINK_MESSAGE_LENGTH(rxmsg->msgid)){_mav_parse_error(status);status->parse_state = MAVLINK_PARSE_STATE_IDLE;break;}
#endif} else {status->parse_state = MAVLINK_PARSE_STATE_GOT_MSGID1;}break;case MAVLINK_PARSE_STATE_GOT_MSGID1:rxmsg->msgid |= c<<8;mavlink_update_checksum(rxmsg, c);status->parse_state = MAVLINK_PARSE_STATE_GOT_MSGID2;break;case MAVLINK_PARSE_STATE_GOT_MSGID2:rxmsg->msgid |= ((uint32_t)c)<<16;mavlink_update_checksum(rxmsg, c);if(rxmsg->len > 0){status->parse_state = MAVLINK_PARSE_STATE_GOT_MSGID3;} else {status->parse_state = MAVLINK_PARSE_STATE_GOT_PAYLOAD;}
#ifdef MAVLINK_CHECK_MESSAGE_LENGTHif (rxmsg->len != MAVLINK_MESSAGE_LENGTH(rxmsg->msgid)){_mav_parse_error(status);status->parse_state = MAVLINK_PARSE_STATE_IDLE;break;}
#endifbreak;case MAVLINK_PARSE_STATE_GOT_MSGID3:_MAV_PAYLOAD_NON_CONST(rxmsg)[status->packet_idx++] = (char)c;mavlink_update_checksum(rxmsg, c);if (status->packet_idx == rxmsg->len){status->parse_state = MAVLINK_PARSE_STATE_GOT_PAYLOAD;}break;case MAVLINK_PARSE_STATE_GOT_PAYLOAD: {const mavlink_msg_entry_t *e = mavlink_get_msg_entry(rxmsg->msgid);uint8_t crc_extra = e?e->crc_extra:0;mavlink_update_checksum(rxmsg, crc_extra);if (c != (rxmsg->checksum & 0xFF)) {status->parse_state = MAVLINK_PARSE_STATE_GOT_BAD_CRC1;} else {status->parse_state = MAVLINK_PARSE_STATE_GOT_CRC1;}rxmsg->ck[0] = c;// zero-fill the packet to cope with short incoming packetsif (e && status->packet_idx < e->max_msg_len) {memset(&_MAV_PAYLOAD_NON_CONST(rxmsg)[status->packet_idx], 0, e->max_msg_len - status->packet_idx);}break;}case MAVLINK_PARSE_STATE_GOT_CRC1:case MAVLINK_PARSE_STATE_GOT_BAD_CRC1:if (status->parse_state == MAVLINK_PARSE_STATE_GOT_BAD_CRC1 || c != (rxmsg->checksum >> 8)) {// got a bad CRC messagestatus->msg_received = MAVLINK_FRAMING_BAD_CRC;} else {// Successfully got messagestatus->msg_received = MAVLINK_FRAMING_OK;}rxmsg->ck[1] = c;if (rxmsg->incompat_flags & MAVLINK_IFLAG_SIGNED) {status->parse_state = MAVLINK_PARSE_STATE_SIGNATURE_WAIT;status->signature_wait = MAVLINK_SIGNATURE_BLOCK_LEN;// If the CRC is already wrong, don't overwrite msg_received,// otherwise we can end up with garbage flagged as valid.if (status->msg_received != MAVLINK_FRAMING_BAD_CRC) {status->msg_received = MAVLINK_FRAMING_INCOMPLETE;}} else {if (status->signing &&(status->signing->accept_unsigned_callback == NULL ||!status->signing->accept_unsigned_callback(status, rxmsg->msgid))) {// If the CRC is already wrong, don't overwrite msg_received.if (status->msg_received != MAVLINK_FRAMING_BAD_CRC) {status->msg_received = MAVLINK_FRAMING_BAD_SIGNATURE;}}status->parse_state = MAVLINK_PARSE_STATE_IDLE;if (r_message != NULL) {memcpy(r_message, rxmsg, sizeof(mavlink_message_t));}}break;case MAVLINK_PARSE_STATE_SIGNATURE_WAIT:rxmsg->signature[MAVLINK_SIGNATURE_BLOCK_LEN-status->signature_wait] = c;status->signature_wait--;if (status->signature_wait == 0) {// we have the whole signature, check it is OKbool sig_ok = mavlink_signature_check(status->signing, status->signing_streams, rxmsg);if (!sig_ok &&(status->signing->accept_unsigned_callback &&status->signing->accept_unsigned_callback(status, rxmsg->msgid))) {// accepted via application level overridesig_ok = true;}if (sig_ok) {status->msg_received = MAVLINK_FRAMING_OK;} else {status->msg_received = MAVLINK_FRAMING_BAD_SIGNATURE;}status->parse_state = MAVLINK_PARSE_STATE_IDLE;if (r_message !=NULL) {memcpy(r_message, rxmsg, sizeof(mavlink_message_t));}}break;}bufferIndex++;// If a message has been sucessfully decoded, check indexif (status->msg_received == MAVLINK_FRAMING_OK){//while(status->current_seq != rxmsg->seq)//{//    status->packet_rx_drop_count++;//               status->current_seq++;//}status->current_rx_seq = rxmsg->seq;// Initial condition: If no packet has been received so far, drop count is undefinedif (status->packet_rx_success_count == 0) status->packet_rx_drop_count = 0;// Count this packet as receivedstatus->packet_rx_success_count++;}if (r_message != NULL) {r_message->len = rxmsg->len; // Provide visibility on how far we are into current msg}if (r_mavlink_status != NULL) {    r_mavlink_status->parse_state = status->parse_state;r_mavlink_status->packet_idx = status->packet_idx;r_mavlink_status->current_rx_seq = status->current_rx_seq+1;r_mavlink_status->packet_rx_success_count = status->packet_rx_success_count;r_mavlink_status->packet_rx_drop_count = status->parse_error;r_mavlink_status->flags = status->flags;}status->parse_error = 0;if (status->msg_received == MAVLINK_FRAMING_BAD_CRC) {/*the CRC came out wrong. We now need to overwrite themsg CRC with the one on the wire so that if thecaller decides to forward the message anyway thatmavlink_msg_to_send_buffer() won't overwrite thechecksum*/if (r_message != NULL) {r_message->checksum = rxmsg->ck[0] | (rxmsg->ck[1]<<8);}}return status->msg_received;
}

此函数首先找到消息标志位 0xFE，然后逐字节的遍历，放入对应的mavlink_message_t结构体中，同时进行CRC检查。mavlink_status_t结构体是检测mavlink_message_t消息的结构体，存储消息的状态。

mavlink接收消息——统一赋值到mavlink_message_t结构体中——然后通过encode代码函数将各个变量成员提取——将变量成员赋值给mavlink_message_t结构体——通过读取真正的消息长度，将消息转换成buffer——mavlink发送消息

mavlink协议关键文件位：

参考博客：https://www.cnblogs.com/warrior1988/p/7729997.html

MAVLink--结构相关推荐

无人机、无人船通信协议——MAVLink（V1.0、V2.0，心跳包，GPS定位，7种飞行模式）
目录 1.什么是MAVLink 2.MAVLink的优势 3.MAVLink信息结构 3.1.MAVLink V1.0 3.2.MAVLink V2.0 4.心跳包(HEARTBEAT MESSAGE ...
PX4读取串口消息，并通过MAVLINK发送给地面站
参考:(131条消息) PX4飞控读取UART串口信息通过Mavlink传给QGC地面站显示_XXX_UUU_XXX的博客-CSDN博客_px4串口2 PX4版本:1.12.1-3 QGC版本: 4. ...
QGC地面站二次开发（三）Qt 简洁地面站
目录多机控制原理多机控制实现简洁地面站优化 1. 飞机的飞行轨迹以不同的颜色区分 2. 控制所有的飞机 3. 将设定航线送给特定的飞机多机控制原理多机地面站支持 TCP. UDP 和串口等三 ...
Pixhawk飞控源码目录结构及编译流程分析
http://blog.csdn.net/xlb7679/article/details/51658956 (PS:这是第一次写博客,以前也有记录一些经验总结心得什么的,不过都是手写笔记或者记在 ...
转载：Pixhawk源码笔记一：APM代码基本结构
转自新浪微博@WalkAnt 基础知识详细参考:http://dev.ardupilot.com/wiki/learning-the-ardupilot-codebase/ 第一部分:介绍详细参 ...
MAVLink 协议解析之XML定义篇
文章目录 1 MAVLink XML 文件的基本结构 2 message 3 enum 1 MAVLink XML 文件的基本结构下面的代码块是 mavlink 消息定义的 xml 数据文档代码块 ...
6005.boost多线程与mavlink协议结合实现消息收发
boost多线程与mavlink协议结合实现消息收发本文将实现boost库创建多线程,利用mavlink协议进行数据链消息打包.解包,解放了很多数据解析的工作,不得不佩服mavlink协议功能的强大 ...
6003.mavlink协议自定义消息编程
mavlink 自定义消息编程紧接着上一篇的操作方法,根据自定义的xml生成基于mavlink协议形式的消息.将其添加到工程中,并且调用起来的示例demo代码如下: 将生成自定义消息目录拷贝到工程下 ...
Mavlink 协议硬解析主要代码
2013-08-16 11:26 1744人阅读评论(1) 收藏举报 [cpp] view plaincopy int MAVLinkProtocol::ParseMsg(BYTE arMsgBu ...
Mavlink协议概要
转:http://blog.csdn.net/luckpl/article/details/52608868#mavlink协议简介 Mavlink协议简介 Mavlink协议简介一Mavlink协 ...

MAVLink--结构

MAVLink源文件结构

mavlink消息包

mavlink解析函数

MAVLink--结构相关推荐

最新文章

热门文章