Enlace del mensaje

Introducción

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.

Constructores de clases

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

Instructor de clase

Destroys the message_link object and releases associated resources.

virtual ~message_link();

Parámetros

Parámetro	Tipo	Descripción
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	El nombre del enlace del mensaje.
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.

Ejemplo

Código para el Robot 1

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

Código para el Robot 2

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

Funciones de los miembros

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:

Código para el Robot 1

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

Código para el Robot 2

// 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

Esta función no tiene ningún parámetro.

Return Values

Esta función devuelve un valor booleano.

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

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

Notes

Es recomendable comprobar siempre que los V5 Brains estén conectados al inicio de un proyecto, antes de ejecutar cualquier otro código.

Examples

Código para el Robot 1

// 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);
  }

Código para el Robot 2

// 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

Envía un mensaje a través de la conexión de enlace.

Available Functions

1 — Envía una cadena de mensaje.

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

Parámetro	Tipo	Descripción
message	const char	El mensaje que se enviará al otro cerebro V5 vinculado.
index	int32_t	Un número entero para enviar al otro cerebro V5 vinculado.
value	double	Un número doble para enviar al otro V5 Brain vinculado. Los números dobles se formatean con 4 decimales; si se proporcionan menos decimales, se agregan ceros al final hasta que se muestren 4.

Return Values

Esta función no devuelve ningún valor.

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.

Código para el Robot 1

// 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);
}

Código para el Robot 2

// 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

Recibe un mensaje de la conexión de enlace.

Available Functions

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

Parameters

Parámetro	Tipo	Descripción
buffer	char	El búfer para almacenar el mensaje recibido.
length	int32_t	La longitud del búfer.
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

Esta función devuelve el número de bytes recibidos.

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.

Código para el Robot 1

// 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);
}

Código para el Robot 2

// 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

Registra una función que se llamará cada vez que el V5 Brain reciba un mensaje.

Available Functions

1 Registra una función de devolución de llamada para todos los mensajes recibidos (mensaje + valor).

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

2 Registra una función de devolución de llamada para todos los mensajes recibidos (mensaje + índice + valor).

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

3 Registra una función de devolución de llamada para un mensaje específico (mensaje + valor).

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

4 Registra una función de devolución de llamada para un mensaje específico (mensaje + índice + valor).

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

Parameters

Parámetro	Tipo	Descripción
message	const char *	El nombre del mensaje que se desea escuchar. Si se omite, la función de devolución de llamada se ejecuta para todos los mensajes recibidos.
callback	Puntero a función	Una función que se ejecuta cuando se recibe un mensaje.

Return Values

Esta función no devuelve ningún valor.

Callback Signature

1 Recibe el nombre del remitente, el nombre del mensaje y el valor.

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

2 Recibe el nombre del remitente, el nombre del mensaje, el índice y el valor.

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

Tipo	Descripción
1st const char *	El nombre del enlace del remitente.
2nd const char *	El nombre del mensaje recibido.
int32_t	El índice asociado al mensaje.
double	El valor asociado al mensaje.

Examples

Código para el Robot 1

// 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);
  }
}

Código para el Robot 2

// 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);
  }
}