MessageLink#

Introduction #

MessageLink 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 MessageLink at the same time, or no messages will be sent/received.

This page uses link as the example MessageLink name. Replace it with your own configured name as needed.

Below is a list of available methods:

is_linked – 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.

Create a Link #

Create a MessageLink on both V5 Brains to establish a communication channel between them—either wirelessly with V5 Radios or through a wired Smart Cable—so the robots can send messages to each other.

MessageLink(smartport, name, linktype, wired)

Parameter	Description
`smartport`	The Smart Port used for this link—the port the V5 Radio is connected to (wireless) or the Smart Cable is plugged into (wired). Written as `Ports.PORTx` where x is the port number.
`name`	The unique name to give this link as a string. Note: This name should be long enough to create a unique ID so it doesn’t accidentally match another team’s link.
`linktype`	The role this Brain will use for this link pair. Each pair must include one Manager and one Worker: `VexlinkType.MANAGER` – Use for the robot that will send more or larger messages. Managers have higher outbound bandwidth (~1040 bytes/sec). `VexlinkType.WORKER` – Use for the robot that will send fewer or smaller messages. Workers have lower outbound bandwidth (~520 bytes/sec).
`wired`	Optional. Whether this link is wired or wireless: `True` – The V5 Brains are connected via a Smart Cable. `False` (default) – The V5 Brains connect wirelessly using V5 Radios.

Code for Robot 1

"""
Create a wireless link in Port 1
name: VEXRoboticsLink123456789
linktype: Manager
"""
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.MANAGER)

Code for Robot 2

"""
Create a wireless link in Port 1
name: VEXRoboticsLink123456789
linktype: Worker
"""
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.WORKER)

Available Methods #

Once your MessageLink is set up and the Brains are linked, you can use the methods below to send, receive, and respond to messages.

is_linked #

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

True – The two V5 Brains are paired and communicating on this link.
False – The two V5 Brains are not paired on this link.

Note: It is good practice to always check to ensure the V5 Brains are linked at the start of a project before running any further code.

Usage:
link.is_linked()

Parameters	Description
	This method has no parameters.

Code for Robot 1

# Tell the other robot when the screen is being pressed

# Create the link
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.MANAGER)

# Do not run code UNTIL the Brains are linked
while not link.is_linked():
    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(50, MSEC)

Code for Robot 2

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

# Create the link
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.WORKER)

# Do not run code UNTIL the Brains are linked
while not link.is_linked():
    wait(0.1, SECONDS)

# Continuously check if Robot 1 has sent "pressed"
while True:
    brain.screen.clear_screen()
    brain.screen.set_cursor(1, 1)
    brain.screen.print("Robot 2 - Worker")
    brain.screen.next_row()

    if link.receive() == "pressed":
        brain.screen.new_line()
        brain.screen.print("Manager is being pressed!")

    wait(50, MSEC)

send #

send sends a string and/or an integer and/or float to the other linked V5 Brain.

Usage:
send(string, integer, float)

Parameters	Description
`string`	The string to send to the other linked V5 Brain.
`integer`	Optional. An integer to send to the other linked V5 Brain.
`float`	Optional. A float to send to the other linked V5 Brain. Floats are formatted to 4 decimal places; if fewer decimals are provided, trailing zeros are added until 4 are shown.

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

If integer and/or float are included, the receiving Brain gets a single encoded string that combines all fields in this order: .string_integer_float

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

Code for Robot 1

# Tell the other robot when the screen is being pressed

# Create the link
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.MANAGER)

# Do not run code UNTIL the Brains are linked
while not link.is_linked():
    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(50, MSEC)

Code for Robot 2

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

# Create the link
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.WORKER)

# Do not run code UNTIL the Brains are linked
while not link.is_linked():
    wait(0.1, SECONDS)

# Continuously check if Robot 1 has sent "pressed"
while True:
    brain.screen.clear_screen()
    brain.screen.set_cursor(1, 1)
    brain.screen.print("Robot 2 - Worker")
    brain.screen.next_row()

    if link.receive() == "pressed":
        brain.screen.new_line()
        brain.screen.print("Manager is being pressed!")

    wait(50, MSEC)

Code for Robot 1

# Tell the other robot where the screen was pressed

# Create the link
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.MANAGER)

# Do not run code UNTIL the Brains are linked
while not link.is_linked():
    wait(0.1, SECONDS)

brain.screen.print("Robot 1 - Manager")
brain.screen.next_row()
brain.screen.print("Tap to send circles")

# Send the coordinates whenever the screen is pressed
while True:
    if brain.screen.pressing():
        x = brain.screen.x_position()
        y = brain.screen.y_position()

        link.send("touch", x, y)

    wait(10, MSEC)

Code for Robot 2

# Draw a circle where Robot 1's screen was pressed

# Create the link
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.WORKER)

# Do not run code UNTIL the Brains are linked
while not link.is_linked():
    wait(0.1, SECONDS)

brain.screen.print("Robot 2 - Worker")

while True:
    # Get the full encoded string
    circle_coordinates = link.receive(200)

    if circle_coordinates:

        # Split the encoded string by _
        parts = circle_coordinates.split("_")

        if len(parts) == 3:
            # Convert the coordinates back into numbers
            x = float(parts[1])
            y = float(parts[2])

            brain.screen.set_fill_color(Color.WHITE)
            brain.screen.draw_circle(x, y, 20)

    wait(10, MSEC)

receive #

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 None, 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.

Usage:
receive(timeout)

Parameters	Description
`timeout`	Optional. How long in milliseconds `receive` will wait for a new message only if the queue is empty. Default is 300,000 (300 seconds).

Code for Robot 1

# Tell the other robot when the screen is being pressed

# Create the link
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.MANAGER)

# Do not run code UNTIL the Brains are linked
while not link.is_linked():
    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(50, MSEC)

Code for Robot 2

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

# Create the link
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.WORKER)

# Do not run code UNTIL the Brains are linked
while not link.is_linked():
    wait(0.1, SECONDS)

# Continuously check if Robot 1 has sent "pressed"
while True:
    brain.screen.clear_screen()
    brain.screen.set_cursor(1, 1)
    brain.screen.print("Robot 2 - Worker")
    brain.screen.next_row()

    if link.receive() == "pressed":
        brain.screen.new_line()
        brain.screen.print("Manager is being pressed!")

    wait(50, MSEC)

Code for Robot 1

# Send a math problem for the other Brain to solve

# Create the link
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.MANAGER)

# Do not run code UNTIL the Brains are linked
while not link.is_linked():
    wait(0.1, SECONDS)

brain.screen.print("Robot 1 - Manager")

"""
Change whether to "add" or "subtract",
then what numbers to use in the operation.
"""
link.send("add", 7, 2.5)

Code for Robot 2

# Solve the math problem that the other Brain sends

# Create the link
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.WORKER)

# Do not run code UNTIL the Brains are linked
while not link.is_linked():
    wait(0.1, SECONDS)

brain.screen.print("Robot 2 - Worker")
brain.screen.next_row()

math_problem = link.receive()

if math_problem:

    # Split the encoded string by _
    parts = math_problem.split("_")

    if len(parts) == 3:
        # Remove the . from the beginning of the string
        operator = "".join([c for c in parts[0] if c.isalpha()])

        # Separate out the numbers for the operation
        a = int(parts[1])
        b = float(parts[2])

        # Use what operator was sent
        if operator == "add":
            result = a + b
        elif operator == "subtract":
            result = a - b
        # If neither add or subtract is sent, do nothing
        else:
            pass

brain.screen.print("Result = ", result)

received #

received registers a function to be called whenever the V5 Brain receives a sent message.

Usage:
link.received(message, arg)

Parameters	Description
`message`	The message name (string) to match. When a received message’s name matches this value, the `callback` function is called.
`callback`	A previously defined function that runs when the V5 Brain receives a message matching `message`.

received callbacks are called with four arguments:

Callback Signature:
callback(message, linkname, index, value)

Argument	Description
`message`	The message name that was received (for example, `“add”`).
`linkname`	The link name the message was received from.
`index`	The integer value sent with the message (if provided).
`value`	The float value sent with the message (if provided).

Code for Robot 1

# Send a math problem for the other Brain to solve

# Create the link
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.MANAGER)

# Do not run code UNTIL the Brains are linked
while not link.is_linked():
    wait(0.1, SECONDS)

brain.screen.print("Robot 1 - Manager")

"""
Change whether to "add" or "subtract",
then what numbers to use in the operation.
"""
link.send("add", 7, 2.5)

Code for Robot 2

# Solve the math problem that the other Brain sends

# Create the link
link = MessageLink(Ports.PORT1, "VEXRoboticsLink123456789", VexlinkType.WORKER)

while not link.is_linked():
    wait(0.1, SECONDS)

brain.screen.print("Robot 2 - Worker")
brain.screen.next_row()

# add if "add" is received
def add_cmd(message, linkname, a, b):
    result = a + b
    brain.screen.print("Result = ", result)

# subtract if ""subtract" is received
def subtract_cmd(message, linkname, a, b):
    result = a - b
    brain.screen.print("Result = ", result)

# Create event handlers for "add" and "subtract"
link.received("add", add_cmd)
link.received("subtract", subtract_cmd)

MessageLink#

Introduction#

Create a Link#

Available Methods#

is_linked#

send#

receive#

received#

Introduction #

Create a Link #

Available Methods #

is_linked #

send #

receive #

received #