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Apollo学习笔记（一）：canbus模块与车辆底盘之间的CAN数据传输过程
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Apollo学习笔记（一）：canbus模块与车辆底盘之间的CAN数据传输过程
博主现在从车载自组网信道分配和多跳路由转向了自动驾驶，没啥经验，想快些做出来个Demo还是得站在巨人的肩膀上才行，我选择了 Apollo ，主要还是支持国产而且它的 开发者套件 有现成的底盘可以直接跑起来，但是apollo系统结构比较复杂，各种花哨的设计模式（ 消息适配器 、 工厂模式 等）绕得人头晕。日本那里有个 autoware 是基于原生ROS的，也用Apollo开发者套件跑了下，就是普通的机器人开发那套，难度适合学生用来做项目，还是得师夷长技以制夷，后面继续深入研究一下。
这次的学习是基于Apollo3.0的，因为3.0还是基于ROS的，后期研究autoware开发自己的系统能用得上，而且那个开发者套件也要用3.0。
canbus模块启动过程
参考知行合一2018大佬的 Apollo Planning模块源代码分析 可以知道canbus模块的主入口为 modules/canbus/main.cc ：
APOLLO_MAIN(apollo::canbus::Canbus);
该宏展开后为：
1 #define APOLLO_MAIN(APP) \
2 int main(int argc, char **argv) { \
3 google::InitGoogleLogging(argv[0]); \
4 google::ParseCommandLineFlags(&argc, &argv, true); \
5 signal(SIGINT, apollo::common::apollo_app_sigint_handler); \
6 APP apollo_app_; \
7 ros::init(argc, argv, apollo_app_.Name()); \
8 apollo_app_.Spin(); \
9 return 0; \
10 }
这里直接引用知行合一2018大神对于Apollo Planning模块的分析：
Main函数完成以下工作：始化Google日志工具，使用Google命令行解析工具解析相关参数，注册接收中止信号“SIGINT”的处理函数：apollo::common::apollo_app_sigint_handler（该函数的功能十分简单，就是收到中止信号“SIGINT”后，调用ros::shutdown()关闭ROS），创建apollo::planning::Planning对象：apollo_app_，初始化ROS环境，调用apollo_app_.Spin()函数开始消息处理循环。
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版权声明：本文为CSDN博主「知行合一2018」的原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/davidhopper/article/details/79176505
更详细的不再赘述，大家可以去上面链接学习。
在 apollo_app_.Spin(); 函数内会依次调用 modules/canbus/canbus.cc 的 Init() 和 Start() 。
Init()主要过程源码分析
1 Status Canbus::Init() {
2 AdapterManager::Init(FLAGS_canbus_adapter_config_filename);/*完成AdapterManager的初始化，
3 FLAGS_canbus_adapter_config_filename对应于modules/canbus/common/canbus_gflags.cc中的
4 DEFINE_string(canbus_adapter_config_filename, "modules/canbus/conf/adapter.conf",
5 "The adapter config file");
6 adapter.conf中配置了canbus模块订阅和发布的topic
7 如果改成原生ROS的话，这里的AdapterManager配置删掉，改成ROS的topic订阅和发布*/
8 AINFO << "The adapter manager is successfully initialized.";
9
10 // load conf
11 //导入配置文件modules/canbus/conf/canbus_conf.pb.txt
12 /*
13 vehicle_parameter {
14 brand: LINCOLN_MKZ//指定车辆，后面生成对应的vehicle_factory，进而生成对应的message_manager_
15 max_enable_fail_attempt: 5
16 driving_mode: COMPLETE_AUTO_DRIVE
17 }
18
19 can_card_parameter {
20 brand: ESD_CAN//指定车辆，后面生成对应的can_client_
21 type: PCI_CARD
22 channel_id: CHANNEL_ID_ZERO
23 }
24
25 enable_debug_mode: false
26 enable_receiver_log: false
27 enable_sender_log: false
28 */
29 //如果改成原生ROS的话此处也可以删除，工厂模式也可以放一边，上面导入的配置文件就是用来生成具体的产品工厂
30 //对象和产品对象，我们直接用ROS跑自己的工程一般车辆和CAN卡是固定的，可以改动后直接生成对应的产品对象
31 if (!common::util::GetProtoFromFile(FLAGS_canbus_conf_file, &canbus_conf_)) {
32 return OnError("Unable to load canbus conf file: " +
33 FLAGS_canbus_conf_file);
34 }
35
36 AINFO << "The canbus conf file is loaded: " << FLAGS_canbus_conf_file;
37 ADEBUG << "Canbus_conf:" << canbus_conf_.ShortDebugString();
38
39 // Init can client
40 auto *can_factory = CanClientFactory::instance();
41 can_factory->RegisterCanClients();
42 can_client_ = can_factory->CreateCANClient(canbus_conf_.can_card_parameter());
43 /*
44 std::unique_ptr<CanClient> CanClientFactory::CreateCANClient(
45 const CANCardParameter& parameter) {
46 auto factory = CreateObject(parameter.brand());//这里确定了新建的can client对象，
47 //此处新建的是ESD CAN卡对应的can client对象（ESD CAN卡是开发者套件用的CAN卡），具体为
48 //modules/drivers/canbus/can_client/esd/esd_can_client.cc的对象。
49 //由此也可以看出modules/canbus/与modules/drivers/canbus/之间的联系是很紧密的，
50 //modules/canbus/偏向上层的针对不同车辆的针对性数据解析
51 //modules/drivers/canbus/偏向底层的一些共性功能的实现，比如
52 //modules/drivers/canbus/can_comm/message_manager就是
53 //modules/canbus/vehicle/lincoln/lincoln_message_manager的父类
54 //改成原生ROS时这两个文件夹可以合到一起
55 if (!factory) {
56 AERROR << "Failed to create CAN client with parameter: "
57 << parameter.DebugString();
58 } else if (!factory->Init(parameter)) {
59 AERROR << "Failed to initialize CAN card with parameter: "
60 << parameter.DebugString();
61 }
62 return factory;
63 }
64 */
65 if (!can_client_) {
66 return OnError("Failed to create can client.");
67 }
68 AINFO << "Can client is successfully created.";
69
70 VehicleFactory vehicle_factory;
71 vehicle_factory.RegisterVehicleFactory();
72 auto vehicle_object =
73 vehicle_factory.CreateVehicle(canbus_conf_.vehicle_parameter());//类似地生成具体的车辆对象
74 if (!vehicle_object) {
75 return OnError("Failed to create vehicle:");
76 }
77
78 message_manager_ = vehicle_object->CreateMessageManager();//生成对应车辆的message_manager_
79 if (message_manager_ == nullptr) {
80 return OnError("Failed to create message manager.");
81 }
82 AINFO << "Message manager is successfully created.";
83 //初始化can_receiver_，就是将can_client_、message_manager_赋给can_receiver_的成员变量
84 if (can_receiver_.Init(can_client_.get(), message_manager_.get(),
85 canbus_conf_.enable_receiver_log()) != ErrorCode::OK) {
86 return OnError("Failed to init can receiver.");
87 }
88 AINFO << "The can receiver is successfully initialized.";
89 //初始化can_sender_，就是将can_client_赋给can_sender_的成员变量
90 if (can_sender_.Init(can_client_.get(), canbus_conf_.enable_sender_log()) !=
91 ErrorCode::OK) {
92 return OnError("Failed to init can sender.");
93 }
94 AINFO << "The can sender is successfully initialized.";
95
96 //生成对应车辆的vehicle_controller_
97 //至此vehicle_object生成了message_manager_和vehicle_controller_
98 //message_manager_ 用来解析canbus从CAN接收到的消息
99 //vehicle_controller_ 用来更新canbus发往CAN的数据对象，也叫作协议类型数据
100 //（如刹车这个命令（协议）对应的对象，apollo将每种命令建了个类，比如林肯的刹车对应的类是
101 //modules/canbus/vehicle/lincoln/protocol/brake_60.h），
102 //也就是canbus接收到上层control的commond后通过vehicle_controller_
103 //更新协议类型数据内的具体成员变量（如刹车这个命令对应的对象内的“刹车量pedal_cmd_”这一成员变量）
104 vehicle_controller_ = vehicle_object->CreateVehicleController();
105 if (vehicle_controller_ == nullptr) {
106 return OnError("Failed to create vehicle controller.");
107 }
108 AINFO << "The vehicle controller is successfully created.";
109
110 /*vehicle_controller_->Init(...) （实际上是
111 modules/canbus/vehicle/lincoln/lincoln_controller.cc中的LincolnController::Init）里面
112 先生成brake_60_等协议类型数据，接着通过
113 can_sender_->AddMessage(Brake60::ID, brake_60_, false);等将brake_60_等协议类型数据
114 加入can_sender_的成员变量send_messages_（向量），后面can_sender_发送数据时就会将send_messages_
115 中的各个协议类型数据包含的CAN帧can_frame_to_send_发送到底盘
116 */
117 if (vehicle_controller_->Init(canbus_conf_.vehicle_parameter(), &can_sender_,
118 message_manager_.get()) != ErrorCode::OK) {
119 return OnError("Failed to init vehicle controller.");
120 }
121 AINFO << "The vehicle controller is successfully initialized.";
122
123 CHECK(AdapterManager::GetControlCommand()) << "Control is not initialized.";
124 CHECK(AdapterManager::GetGuardian()) << "Guardian is not initialized.";
125 // TODO(QiL) : depreacte this
126 //类似原生ROS的添加回调函数，Apollo将topic的发布和订阅都集成到了AdapterManager进行统一管理
127 //Canbus::OnControlCommand就是canbus模块对上层cotrol_command的回调函数
128 if (!FLAGS_receive_guardian) {
129 AdapterManager::AddControlCommandCallback(&Canbus::OnControlCommand, this);
130 } else {
131 AdapterManager::AddGuardianCallback(&Canbus::OnGuardianCommand, this);
132 }
133
134 return Status::OK();
135 }
Init()主要过程流程图（为方便整合不严格按照代码里的顺序）
Start()主要过程源码分析
1 /*Init()生成的对象有can_client_ , vehicle_object , message_manager_,
2 vehicle_controller_ , can_receiver_ 和 can_sender_，
3 Start()里面就是调用can_client_, can_receiver_, can_sender_和vehicle_controller_的Start()将
4 它们的功能各自启动起来，比如can_client_ 的Start() （实际上是
5 modules/drivers/canbus/can_client/esd/esd_can_client.cc的Start()）
6 就是调用third_party/can_card_library/esd_can/include/ntcan.h的内置函数canOpen()等设置端口等
7 以启动CAN卡，ntcan.h是买CAN卡的时候附带光盘里的文件，买了开发者套件装好CAN卡以后要把这个文件拷到
8 third_party/can_card_library/esd_can/include/下使用。因为ntcan.h是花钱买的所以就不把ntcan.h
9 的代码放上来了。
10
11 最后启动定时器循环运行Canbus::OnTimer，OnTimer这个函数就是发布底盘信息用的，发布以后
12 订阅底盘topic的上层模块就能接收到底盘信息。
13 */
14 Status Canbus::Start() {
15 // 1. init and start the can card hardware
16 if (can_client_->Start() != ErrorCode::OK) {
17 return OnError("Failed to start can client");
18 }
19 AINFO << "Can client is started.";
20
21 // 2. start receive first then send
22 if (can_receiver_.Start() != ErrorCode::OK) {
23 return OnError("Failed to start can receiver.");
24 }
25 AINFO << "Can receiver is started.";
26
27 // 3. start send
28 if (can_sender_.Start() != ErrorCode::OK) {
29 return OnError("Failed to start can sender.");
30 }
31
32 // 4. start controller
33 if (vehicle_controller_->Start() == false) {
34 return OnError("Failed to start vehicle controller.");
35 }
36
37 // 5. set timer to triger publish info periodly
38 const double duration = 1.0 / FLAGS_chassis_freq;
39 timer_ = AdapterManager::CreateTimer(ros::Duration(duration),
40 &Canbus::OnTimer, this);
41
42 // last step: publish monitor messages
43 apollo::common::monitor::MonitorLogBuffer buffer(&monitor_logger_);
44 buffer.INFO("Canbus is started.");
45
46 return Status::OK();
47 }
Start()主要过程流程图
下面分 canbus模块向底盘发送数据 和 canbus模块从底盘接收数据 两部分进行深入分析。
canbus模块向底盘发送数据
主要过程
canbus模块向底盘发送数据的开端在canbus模块接收到上层control_command，因此Canbus::OnControlCommand是发送的开端。
1 void Canbus::OnControlCommand(const ControlCommand &control_command) {
2 int64_t current_timestamp =
3 apollo::common::time::AsInt64<common::time::micros>(Clock::Now());
4 // if command coming too soon, just ignore it.
5 if (current_timestamp - last_timestamp_ < FLAGS_min_cmd_interval * 1000) {
6 ADEBUG << "Control command comes too soon. Ignore.\n Required "
7 "FLAGS_min_cmd_interval["
8 << FLAGS_min_cmd_interval << "], actual time interval["
9 << current_timestamp - last_timestamp_ << "].";
10 return;
11 }
12
13 last_timestamp_ = current_timestamp;
14 ADEBUG << "Control_sequence_number:"
15 << control_command.header().sequence_num() << ", Time_of_delay:"
16 << current_timestamp - control_command.header().timestamp_sec();
17
18 /*从此处开始的vehicle_controller_->Update(control_command)和can_sender_.Update()是关键
19 正如之前所提到的，vehicle_controller_->Update(control_command)用来更新协议类型数据的
20 成员变量，接着can_sender_.Update()把更新之后的数据通过can_frame_to_update_
21 赋值给can_frame_to_send_，can_sender_在Start()是开启的发送线程将can_frame_to_send_
22 通过CAN卡附带驱动内的canWrite()函数注入底盘CAN网络
23
24 这两个Update()涉及的函数比较多，中间挺多跳转，就不放源码了，跳转的过程在后面流程图中给出，具体代码的
25 实现大家还是需要自己去看代码
26 */
27 if (vehicle_controller_->Update(control_command) != ErrorCode::OK) {
28 AERROR << "Failed to process callback function OnControlCommand because "
29 "vehicle_controller_->Update error.";
30 return;
31 }
32 can_sender_.Update();
33 }
vehicle_controller_->Update流程图（以刹车对应的协议类型数据为例）
can_sender_.Update()流程图（以刹车对应的协议类型数据为例）
canbus模块从底盘接收数据
主要过程
在canbus Start()的时候，can_receiver_.Start()启动了从底盘接收数据的线程，线程内运行CanReceiver::RecvThreadFunc()
1 // 2. start receive first then send
2 if (can_receiver_.Start() != ErrorCode::OK) {
3 return OnError("Failed to start can receiver.");
4 }
5 AINFO << "Can receiver is started.";
6
7 template <typename SensorType>
8 ::apollo::common::ErrorCode CanReceiver<SensorType>::Start() {
9 if (is_init_ == false) {
10 return ::apollo::common::ErrorCode::CANBUS_ERROR;
11 }
12 is_running_ = true;
13
14 thread_.reset(new std::thread([this] { RecvThreadFunc(); }));
15 if (thread_ == nullptr) {
16 AERROR << "Unable to create can client receiver thread.";
17 return ::apollo::common::ErrorCode::CANBUS_ERROR;
18 }
19 return ::apollo::common::ErrorCode::OK;
20 }
RecvThreadFunc()内循环运行can_client_->Receive(&buf, &frame_num)
1 template <typename SensorType>
2 void CanReceiver<SensorType>::RecvThreadFunc() {
3 AINFO << "Can client receiver thread starts.";
4 CHECK_NOTNULL(can_client_);
5 CHECK_NOTNULL(pt_manager_);
6
7 int32_t receive_error_count = 0;
8 int32_t receive_none_count = 0;
9 const int32_t ERROR_COUNT_MAX = 10;
10 std::chrono::duration<double, std::micro> default_period{10 * 1000};
11
12 while (IsRunning()) {
13 std::vector<CanFrame> buf;
14 int32_t frame_num = MAX_CAN_RECV_FRAME_LEN;
15 if (can_client_->Receive(&buf, &frame_num) !=
16 ::apollo::common::ErrorCode::OK) {
17 /*
18 can_client_为modules/drivers/canbus/can_client/esd/esd_can_client.cc的实例化对象，
19 其Receive()函数调用了third_party/can_card_library/esd_can/include/ntcan.h的canRead函数从
20 CAN网络中读取数据并存入buf，
21 const int32_t ret = canRead(dev_handler_, recv_frames_, frame_num, nullptr);
22 buf的定义是std::vector<CanFrame> buf;
23 CanFrame在之前can_sender_.Update()流程图内有分析。
24 */
25 LOG_IF_EVERY_N(ERROR, receive_error_count++ > ERROR_COUNT_MAX,
26 ERROR_COUNT_MAX)
27 << "Received " << receive_error_count << " error messages.";
28 std::this_thread::sleep_for(default_period);
29 continue;
30 }
31 receive_error_count = 0;
32
33 if (buf.size() != static_cast<size_t>(frame_num)) {
34 AERROR_EVERY(100) << "Receiver buf size [" << buf.size()
35 << "] does not match can_client returned length["
36 << frame_num << "].";
37 }
38
39 if (frame_num == 0) {
40 LOG_IF_EVERY_N(ERROR, receive_none_count++ > ERROR_COUNT_MAX,
41 ERROR_COUNT_MAX)
42 << "Received " << receive_none_count << " empty messages.";
43 std::this_thread::sleep_for(default_period);
44 continue;
45 }
46 receive_none_count = 0;
47
48 for (const auto &frame : buf) {
49 uint8_t len = frame.len;
50 uint32_t uid = frame.id;
51 const uint8_t *data = frame.data;
52 pt_manager_->Parse(uid, data, len);
53 /*
54 pt_manager_在Init时被赋值为message_manager_（modules/canbus/vehicle/lincoln
55 /lincoln_message_manager.cc的实例化对象），message_manager_用来解析从CAN网络获取的CanFrame
56 */
57 if (enable_log_) {
58 ADEBUG << "recv_can_frame#" << frame.CanFrameString();
59 }
60 }
61 std::this_thread::yield();
62 }
63 AINFO << "Can client receiver thread stopped.";
64 }
接收CAN数据流程图
至于chassis_datail找不到的问题大家可以从 https://blog.csdn.net/M_Alan_walker/article/details/88823610 的最后面获得解答。
博主主要是从 https://blog.csdn.net/M_Alan_walker/article/details/88823610 学习的，加入一些自己的理解，有些分析得不完善的地方大家在上面的网址可以得到更详细的补充。
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