消息链接

介绍

The message_link class lets two V5 Brains communicate by sending short string messages with optional small data. It’s designed for robot-to-robot coordination — like starting routines, sharing sensor results, or triggering behaviors on another robot.

Every usage of send adds a message to the linked V5 Brain’s queue, and the queue is read first-in, first-out (FIFO). If multiple messages are sent before the other V5 Brain uses receive, they will be stored and returned one at a time in the order they were sent. Because messages can queue, repeatedly sending the same status every loop may create backlog; for time-critical logic, send only when values change.

Important: Both robots must be running projects that use message_link at the same time, or no messages will be sent/received.

类构造函数

message_link( 
  int32_t     index, 
  const char  *name, 
  linkType    type, 
  bool        isWired = false );

类析构函数

Destroys the message_link object and releases associated resources.

virtual ~message_link();

参数

范围	类型	描述
index	int32_t	The Smart Port that the V5 Radio, or the Smart Cable, is connected to, written as PORTx, where x is the port number (for example, PORT1).
name	char	消息链接的名称。
type	linkType	The type of link, either linkType::manager or linkType::worker. This information is used to correctly configure the radio and also determines available bandwidth for transmission and reception. A manager robot has double the available bandwidth (1040 bytes/second) to send information to the worker robot (520 bytes/second). linkType::manager - The message_link object is a manager. linkType::worker - The message_link object is a worker.
isWired	bool	Whether the message_link object is wired. true - The message_link object is wired. false - The message_link object is wireless.

例子

机器人 1 的代码

// Create a wireless link in Port 1
message_link link = message_link(
  PORT1, // index
  "VEXRoboticsLink123456789", // name
  linkType::manager, // type
  true); // isWired

机器人2的代码

// Create a wireless link in Port 1
message_link link = message_link(
  PORT1, // index
  "VEXRoboticsLink123456789", // name
  linkType::worker, // type
  true); // isWired

成员功能

The message_link class includes the following member functions:

• isLinked — Returns whether this Brain is actively connected to its paired Brain.

• send — Sends a message to the paired Brain.

• receive — Waits for and returns the next incoming message.

• received — Registers a function to be called whenever a new message is received.

Before calling any message_link member functions, a message_link instance must be created, as shown below:

机器人 1 的代码

// Create a wireless link in Port 1
message_link link = message_link(
  PORT1, // index
  "VEXRoboticsLink123456789", // name
  linkType::manager, // type
  true); // isWired

机器人2的代码

// Create a wireless link in Port 1
message_link link = message_link(
  PORT1, // index
  "VEXRoboticsLink123456789", // name
  linkType::worker, // type
  true); // isWired

isLinked

isLinked method returns whether the V5 Brains on a MessageLink are paired with one another.

Available Functions

bool isLinked();

Parameters

此函数没有任何参数。

Return Values

此函数返回一个布尔值。

• true – The two V5 Brains are paired and communicating on this link.

• false – The two V5 Brains are not paired on this link.

Notes

在项目开始时，运行任何其他代码之前，最好始终检查以确保 V5 Brains 已连接。

Examples

机器人 1 的代码

// Tell the other robot when the screen is being pressed
  // Create the link
  message_link link = message_link(PORT1, "VEXRoboticsLink123456789", linkType::manager, true);

  // Do not run code UNTIL the Brains are linked
  while (!link.isLinked()){
    wait(0.1, seconds);
  }

  Brain.Screen.print("Robot 1 - Manager");

  // Continuously send if the screen is being pressed
  while (true){
    if (Brain.Screen.pressing()){
      link.send("pressed");
    } else {
      link.send("released");
    }
    wait(0.05, seconds);
  }

机器人2的代码

// Display if the other robot's screen is being pressed

  // Create the link
  message_link link = message_link(PORT1, "VEXRoboticsLink123456789", linkType::worker, true);
  
  // Do not run code UNTIL the Brains are linked
  while (!link.isLinked()){
   wait(0.1, seconds);
  }

  // Continuously check if Robot 1 has sent "pressed"
  while (true){
    Brain.Screen.clearScreen();
    Brain.Screen.setCursor(1, 1);
    Brain.Screen.print("Robot 2 - Worker");
    Brain.Screen.newLine();
    char msg[32] = {0};                         // buffer for incoming message
    int32_t n = link.receive(msg, sizeof(msg), 100);  // wait up to 100ms
    if (n > 0 && strcmp(msg, "pressed") == 0) {
      Brain.Screen.newLine();
      Brain.Screen.print("Manager is being pressed!");
    }
    wait(0.05, seconds);
  }

send

通过链路连接发送消息。

Available Functions

1 — 发送消息字符串。

int32_t send( 
  const char *message );

2 — Sends a message string with a double.

int32_t send( 
  const char *message, 
  double      value );

3 — Sends a message string with an int32_t and a double.

int32_t send(
  const char *message, 
  int32_t     index, 
  double      value );

Parameters

范围	类型	描述
message	const char	要发送给另一个已连接的 V5 大脑的消息。
index	int32_t	要发送给另一个已连接的 V5 大脑的整数。
value	double	发送给另一个已连接的 V5 Brain 的双精度浮点数。双精度浮点数默认显示 4 位小数；如果提供的位数少于 4 位，则会在末尾添加零，直到显示 4 位小数为止。

Return Values

此函数不返回任何值。

Notes

If only message is sent, the other linked V5 Brain receives that exact message.

If value (and index if provided) are included, the receiving Brain gets a single encoded message that combines all fields in this order: .message_index_value

Examples

Using link.send(“string”, 1, 2.55) is received as .string_1_2.5500.

机器人 1 的代码

// Tell the other robot when the screen is being pressed

// Create the link
message_link link = message_link(PORT1, "VEXRoboticsLink123456789", linkType::manager, true);

// Do not run code UNTIL the Brains are linked
while (!link.isLinked()){
  wait(0.1, seconds);
}

Brain.Screen.print("Robot 1 - Manager");

// Continuously send if the screen is being pressed
while (true){
  if (Brain.Screen.pressing()){
    link.send("pressed");
  } else {
    link.send("released");
  }
  wait(0.05, seconds);
}

机器人2的代码

// Display if the other robot's screen is being pressed

// Create the link
message_link link = message_link(PORT1, "VEXRoboticsLink123456789", linkType::worker, true);

// Do not run code UNTIL the Brains are linked
while (!link.isLinked()){
  wait(0.1, seconds);
}
// Continuously check if Robot 1 has sent "pressed"
while (true){
  Brain.Screen.clearScreen();
  Brain.Screen.setCursor(1, 1);
  Brain.Screen.print("Robot 2 - Worker");
  Brain.Screen.newLine();
  char msg[32] = {0};  // buffer for incoming message
  int32_t n = link.receive(msg, sizeof(msg), 100);  // wait up to 100ms
  if (n > 0 && strcmp(msg, "pressed") == 0) {
    Brain.Screen.newLine();
    Brain.Screen.print("Manager is being pressed!");
  }
  wait(0.05, seconds);
}

receive

接收来自链路连接的消息。

Available Functions

int32_t receive(
  char     *buffer,
  int32_t   length, 
  int32_t   timeoutMs = 500 );

Parameters

范围	类型	描述
buffer	char	用于存储接收到的消息的缓冲区。
length	int32_t	缓冲区长度。
timeoutMs	int32_t	How long in milliseconds receive will wait for a new message only if the queue is empty. Default is 300,000 (300 seconds).

Return Values

此函数返回接收到的字节数。

Notes

• receive returns the next queued message from the other linked V5 Brain. Messages are read in FIFO order (oldest unread first). If the queue is empty when receive is called, it waits up to the specified timeout for a new message. If no message arrives in that window, receive returns 0, and any message sent afterward remains in the queue to be read the next time receive is used.

• If the other linked V5 Brain sent only a string, receive returns that exact string.

• If the other linked V5 Brain sent an integer and/or float, receive returns a single encoded string that combines all fields in this order: .string_integer_float

  • For example, if the other linked V5 Brain uses link.send(“string”, 1, 2.55), then using link.receive() returns an encoded string such as .string_1_2.5500. You can split this encoded string (see the examples below) to extract the message name, integer, and float values.

  • If you’d rather avoid manual splitting/parsing, use received to register a handler for a specific message name; the handler receives the sent values as arguments.

Examples

Using link.send(“string”, 1, 2.55) is received as .string_1_2.5500.

机器人 1 的代码

// Tell the other robot when the screen is being pressed

// Create the link
message_link link = message_link(PORT1, "VEXRoboticsLink123456789", linkType::manager, true);

// Do not run code UNTIL the Brains are linked
while (!link.isLinked()){
  wait(0.1, seconds);
}

Brain.Screen.print("Robot 1 - Manager");

// Continuously send if the screen is being pressed
while (true){
  if (Brain.Screen.pressing()){
    link.send("pressed");
  } else {
    link.send("released");
  }
  wait(0.05, seconds);
}

机器人2的代码

// Display if the other robot's screen is being pressed

// Create the link
message_link link = message_link(PORT1, "VEXRoboticsLink123456789", linkType::worker, true);

// Do not run code UNTIL the Brains are linked
while (!link.isLinked()){
  wait(0.1, seconds);
}
// Continuously check if Robot 1 has sent "pressed"
while (true){
  Brain.Screen.clearScreen();
  Brain.Screen.setCursor(1, 1);
  Brain.Screen.print("Robot 2 - Worker");
  Brain.Screen.newLine();
  char msg[32] = {0};   // buffer for incoming message
  int32_t n = link.receive(msg, sizeof(msg), 100);  // wait up to 100ms
  if (n > 0 && strcmp(msg, "pressed") == 0) {
    Brain.Screen.newLine();
    Brain.Screen.print("Manager is being pressed!");
  }
  wait(0.05, seconds);
}

received

注册一个函数，当 V5 大脑收到发送的消息时，该函数将被调用。

Available Functions

1 为所有收到的消息（消息 + 值）注册回调函数。

void received(
    void (* callback)(const char *, const char *, double)
);

2 为所有收到的消息注册一个回调函数（消息 + 索引 + 值）。

void received(
    void (* callback)(const char *, const char *, int32_t, double)
);

3 为特定消息（消息 + 值）注册回调。

void received(
    const char *message,
    void      (* callback)(const char *, const char *, double)
);

4 为特定消息注册回调（消息 + 索引 + 值）。

void received(
    const char *message,
    void      (* callback)(const char *, const char *, int32_t, double)
);

Parameters

范围	类型	描述
message	const char *	要监听的消息名称。如果省略，则回调函数将对所有接收到的消息运行。
callback	函数指针	收到消息时执行的函数。

Return Values

此函数不返回任何值。

Callback Signature

1 接收发件人姓名、消息名称和值。

void callback(const char *, const char *, double)

2 接收发件人姓名、消息名称、索引和值。

void callback(const char *, const char *, int32_t, double)

类型	描述
1st const char *	发件人链接名称。
2nd const char *	收到的消息名称。
int32_t	与该消息关联的索引。
double	与消息关联的值。

Examples

机器人 1 的代码

// Send whether screen is pressed on left or right
void screen_pressed() {
  if (Brain.Screen.xPosition() < 240) {
    link.send("left");
  } else {
    link.send("right");
  }
}

int main() {
  /* vexcodeInit() is only required when using VEXcode.
  Remove vexcodeInit() if compiling in VS Code. */
  vexcodeInit();
  
// Create the link
  message_link link(PORT1, "LeftRightLink", linkType::manager, true);

// Do not run code UNTIL the Brains are linked
  while (!link.isLinked()) {
    wait(0.1, seconds);
  }

  Brain.Screen.print("Robot 1 - Manager");

  Brain.Screen.pressed(screen_pressed);

  while (true) {
    wait(10, msec);
  }
}

机器人2的代码

// Create variable to track where screen is pressed
int lastPress = 0;

// Update the variable whenever a new message is received
void message_received(const char* message, const char* linkname, double timestamp) {
  if (strcmp(message, "left") == 0)  lastPress = 1;
  if (strcmp(message, "right") == 0) lastPress = 2;
}

int main() {
  /* vexcodeInit() is only required when using VEXcode.
  Remove vexcodeInit() if compiling in VS Code. */
  vexcodeInit();

// Create the link
  message_link link(PORT1, "VEXRoboticsLink123456789", linkType::worker, true);

// Do not run code UNTIL the Brains are linked
  while (!link.isLinked()) {
    wait(0.1, seconds);
  }

  link.received(message_received);

  // Display if Robot 1's screen was pressed on the left or right
  while (true) {
    Brain.Screen.clearScreen();
    Brain.Screen.setCursor(1, 1);
    Brain.Screen.print("Robot 2 - Worker");
    Brain.Screen.newLine();

    if (lastPress == 1) {
      Brain.Screen.print("Manager pressed LEFT");
    } else if (lastPress == 2) {
      Brain.Screen.print("Manager pressed RIGHT");
    } else {
      Brain.Screen.print("Waiting...");
    }

    wait(0.1, seconds);
  }
}