Drivetrain#

Introduction #

The VEX IQ (2nd gen) robot uses a drivetrain to drive and turn. A drivetrain is made of motors and wheels that work together to move the robot.

A configured drivetrain can use a connected Gyro Sensor, the Brain’s built-in Inertial Sensor, or no sensor. When a sensor is used, the drivetrain uses it to help the robot move and turn precisely. At the start of each project, the drivetrain calibrates the sensor automatically. Keep the robot still for about 2 seconds during calibration, so the robot can move and turn correctly.

There are many ways to code the drivetrain. Below is a list of all Drivetrain blocks:

Actions — Move and turn the robot.

drive — Moves the robot forward or reverse forever.
drive for — Moves the robot forward or reverse for a specific distance.
turn — Turns the robot left or right forever.
turn for — Turns the robot left or right for a specific number of degrees.
turn to heading — Turns the robot to face a specific heading from -359 to 359 degrees. The robot will turn the shortest direction to reach the target heading.
turn to rotation — Turns the robot to a specific rotation.
stop driving — Stops the robot’s movement.

Settings — Adjust drivetrain settings.

set drive velocity — Tells the robot how fast to drive.
set turn velocity — Tells the robot how fast to turn.
set drive stopping — Tells how the robot will stop moving: by braking, coasting, or holding.
set drive timeout — Sets how many seconds the robot will try to finish a movement.
set drive heading — Changes the robot’s current heading to a new heading.
set drive rotation — Changes the robot’s current rotation to a new rotation.

Values — Check movement status.

drive is done — Reports whether the robot is finished moving.
drive is moving — Reports whether the robot is moving.
drive heading — Reports the robot’s current heading from 0 to 359 degrees.
drive rotation — Reports the robot’s current rotation.
drive velocity — Reports how fast the robot is driving.
drive current — Reports how much electrical current the drivetrain is using.

Actions #

drive #

The drive stack block moves the robot forward or reverse forever. The robot will continue to move until it is given another action, like turning or stopping.

  drive [forward v]

Parameters	Description
direction	The direction the robot moves: forward or reverse.

Example

  when started
  [Drive forward, then stop.]
  drive [forward v]    
  wait (2) seconds
  stop driving

drive for #

The drive for stack block moves the robot forward or reverse for a specific distance. The project will wait until the robot is done moving before the next block in the stack runs.

  drive [forward v] for (200) [mm v] ▶

Parameters	Description
direction	The direction the robot moves: forward or reverse.
distance	The distance the robot drives. This can be an integer or a decimal.
unit	The distance unit: mm (millimeters) or inches.
and don’t wait	Select the arrow ( ▶ ) to expand the block to say and don’t wait, so the next block in the stack will run right away.

Example

  when started
  [Drive backward 500 mm (millimeters).]
  drive [reverse v] for (500) [mm v] ▶

turn #

The turn stack block turns the robot left or right forever. The robot will continue to turn until it is given another action, like driving or stopping.

  turn [right v]

Parameters	Description
direction	The direction the robot turns: left or right.

Example

  when started
  [Turn right, then stop.]
  turn [right v]
  wait (2) seconds    
  stop driving

turn for #

The turn for stack block turns the robot left or right for a specific number of degrees. The turn is relative to the current position of the robot. The project will wait until the robot is done turning before the next block in the stack runs.

  turn [right v] for (90) degrees ▶

Parameters	Description
direction	The direction the robot turns: left or right.
angle	The number of degrees the robot turns. This can be an integer or a decimal.
and don’t wait	Select the arrow ( ▶ ) to expand the block to say and don’t wait, so the next block in the stack will run right away.

Example

  when started
  [Turn left, then turn around to the right.]
  turn [left v] for (90) degrees ▶
  turn [right v] for (180) degrees ▶

turn to heading #

A heading is the direction the robot is facing, measured in degrees. The turn to heading stack block turns the robot to face a specific heading from -359 to 359 degrees. The robot will turn the shortest direction to reach the target heading.

The robot’s starting heading is 0 degrees.

The project will wait until the robot is done turning before the next block in the stack runs.

  turn to heading (90) degrees ▶

Parameters	Description
heading	The direction the robot should face, in degrees. This can be an integer or a decimal from -359 to 359.
and don’t wait	Select the arrow ( ▶ ) to expand the block to say and don’t wait, so the next block in the stack will run right away.

Example

  when started
  [Turn to face the cardinal directions.]
  turn to heading (90) degrees ▶
  wait (2) seconds
  turn to heading (180) degrees ▶
  wait (2) seconds
  turn to heading (270) degrees ▶
  wait (2) seconds
  turn to heading (0) degrees ▶
  wait (2) seconds

turn to rotation #

The turn to rotation stack block turns the robot to a specific rotation.

Rotation is how much the robot has turned, measured in degrees. At the beginning of a project, the rotation value is set to 0 degrees. Rotation can also be set using the set drive rotation block.

Rotation values are absolute. This means the direction of the turn depends on the robot’s current rotation. Turning right increases the rotation, and turning left decreases the rotation.

For example, if the robot starts at 0 degrees and you turn to a rotation of 720 degrees, it will turn right twice. If you then turn to a rotation of 360 degrees, it will turn left once, because 360 is less than 720.

  turn to rotation (90) degrees ▶

Parameters	Description
rotation	The rotation value, in degrees, that the robot will turn to. This can be an integer or a decimal.
and don’t wait	Select the arrow ( ▶ ) to expand the block to say and don’t wait, so the next block in the stack will run right away.

Example

  when started
  [Turn left, then spin in a circle clockwise and face right.]
  turn to rotation (-90) degrees ▶
  wait (2) seconds
  turn to rotation (450) degrees ▶

stop driving #

The stop driving stack block stops the robot’s movement.

  stop driving

Parameters	Description
	This block has no parameters.

Example

  when started
  [Drive forward, then stop.]
  drive [forward v]
  wait [4] seconds
  stop driving

Settings #

set drive velocity #

The set drive velocity stack block tells the robot how fast to drive. A higher velocity makes the robot drive faster and a lower velocity makes the robot drive slower.

Every project begins with the robot driving at 50% velocity by default.

Note: A higher velocity makes the robot drive faster, but it may be less precise. A lower velocity makes the robot drive slower, but it can be more precise.

  set drive velocity to (50) [% v]

Parameters	Description
velocity	The velocity to drive with from 0% to 100% when using %. rpm (revolutions per minute) uses values from 0 to 120.
unit	The unit of measurement: % or rpm (revolutions per minute).

Example

  when started
  [Drive forward at the default velocity.]
  drive [forward v] for (100) [mm v] ▶
  wait (1) seconds
  [Move slower.]
  set drive velocity to (20) [% v]
  drive [forward v] for (100) [mm v] ▶
  wait (1) seconds
  [Move faster.]
  set drive velocity to (100) [% v]
  drive [forward v] for (100) [mm v] ▶
  wait (1) seconds

set turn velocity #

The set turn velocity stack block tells the robot how fast to turn. A higher velocity makes the robot turn faster and a lower velocity makes the robot turn slower.

Every project begins with the robot turning at 50% velocity by default.

Note: A higher velocity makes the robot turn faster, but it may be less precise. A lower velocity makes the robot turn slower, but it can be more precise.

  set turn velocity to (50) [% v]

Parameters	Description
velocity	The velocity to turn with from 0% to 100% when using %. rpm (revolutions per minute) uses values from 0 to 120.
unit	The unit of measurement: % or rpm (revolutions per minute).

Example

  when started
  [Turn at default velocity.]
  turn [right v] for (100) degrees ▶
  wait (1) seconds
  [Turn slower.]
  set turn velocity to (20) [% v]
  turn [right v] for (100) degrees ▶
  wait (1) seconds
  [Turn faster.]
  set turn velocity to (100) [% v]
  turn [right v] for (100) degrees ▶
  wait (1) seconds

set drive stopping #

The set drive stopping stack block sets how the robot will stop moving: by braking, coasting, or holding.

  set drive stopping to [brake v]

Parameters	Description
stopping behavior	How the robot will stop: brake — Stops immediately. coast — Slows to a stop. hold — Stops immediately and holds the wheels’ position.

Parameters

Description

stopping behavior

How the robot will stop:

brake — Stops immediately.
coast — Slows to a stop.
hold — Stops immediately and holds the wheels’ position.

If this block is not used, the robot will use brake when stopping.

Example

  when started
  [Drive forward and coast to a stop.]
  set drive velocity to (100) [% v]
  set drive stopping to [coast v]
  drive [forward v]
  wait (2) seconds
  stop driving

set drive timeout #

The set drive timeout stack block sets how many seconds the robot will try to finish a movement. If the robot cannot finish in that time, it will stop trying and move on to the next block in the stack. This keeps the robot from getting stuck on a movement.

  set drive timeout to (1) seconds

Parameters	Description
time	The number of seconds the robot can try to finish a movement. This can be an integer or a decimal.

Example

  when started
  [Drive forward for 1 second, then turn.]
  set drive timeout to (1) seconds
  drive [forward v] for (25) [inches v] ▶
  turn [right v] for (90) degrees ▶

set drive heading #

A heading is the direction the robot is facing, measured in degrees. The set drive heading stack block changes the robot’s current heading to a new heading value.

For example, if the robot has turned to face right, setting the heading to 0 degrees makes that right-facing position the new 0 degrees. Then the robot can turn to other positions based on that new heading.

  set drive heading to (0) degrees

Parameters	Description
heading	The heading value, in degrees, to set for the robot. This can be an integer or a decimal from 0 to 359.

Example

  when started
  [Turn to the left.]
  set drive heading to (90) degrees
  turn to heading (0) degrees ▶

set drive rotation #

Rotation is how much the robot has turned, measured in degrees. At the beginning of a project, the rotation value is set to 0 degrees. The set drive rotation stack block changes the robot’s current rotation to a new value.

For example, if the robot has made two full turns to the right, its rotation value will be 720 degrees. Setting the rotation to 0 degrees will reset that rotation from 720 to 0 degrees. Then the robot can turn to rotations based on that new value.

  set drive rotation to (0) degrees

Parameters	Description
rotation	The rotation value, in degrees, to set for the robot. This can be an integer or a decimal.

Example

  when started
  [Spin counterclockwise two times.]
  set drive rotation to (720) degrees
  turn to rotation (0) degrees ▶

Values #

drive is done #

The drive is done Boolean block reports whether the robot is finished moving. This can be used to control the timing of other behaviors based on the robot’s movement.

True — The robot is finished moving.
False — The robot is still moving.

This block works together with the following Drivetrain blocks that have the and don’t wait parameter: drive for, turn for, turn to heading, and turn to rotation.

    <drive is done?>

Parameters	Description
	This block has no parameters.

Example

    when started
    [Start spinning when the drive is complete.]
    drive [forward v] for (200) [mm v] ◀ and don't wait
    forever
    if <drive is done?> then
    turn [right v] for (360) degrees ▶
    break
    else
    set cursor to row (1) column (1) on screen
    print [Still Moving...] on screen ▶
    wait (0.1) seconds
    clear screen

drive is moving #

The drive is moving Boolean block reports whether the robot is moving. This can be used to control the timing of other behaviors based on the robot’s movement.

True — The robot is moving.
False — The robot is not moving.

This block works together with the following Drivetrain blocks that have the and don’t wait parameter: drive for, turn for, turn to heading, and turn to rotation.

    <drive is moving?>

Parameters	Description
	This block has no parameters.

Example

    when started
    [Print that the robot is moving while it is still driving.]
    drive [forward v] for (200) [mm v] ◀ and don't wait
    while <drive is moving?>
    set cursor to row (1) column (1) on screen
    print [Still Moving...] on screen ▶
    wait (0.1) seconds
    clear screen
    end
    set cursor to row (1) column (1) on screen
    print [Done!] on screen ▶

drive heading #

A heading is the direction the robot is facing, measured in degrees. The drive heading reporter block reports the robot’s current heading from 0 to 359 degrees.

The robot’s starting heading is 0 degrees.

    (drive heading in degrees)

Parameters	Description
	This block has no parameters.

Example

    when started
    [Display the heading after turning.]
    turn [right v] for (450) degrees ▶
    print (drive heading in degrees) on screen ◀ and set cursor to next row

drive rotation #

Rotation is how much the robot has turned, measured in degrees. At the beginning of a project, the rotation value is set to 0 degrees. The drive rotation reporter block reports the robot’s current rotation.

Turning right increases the rotation, and turning left decreases the rotation. For example, making two full turns to the right will report a rotation of 720 degrees.

    (drive rotation in degrees)

Parameters	Description
	This block has no parameters.

Example

    when started
    [Display the rotation after turning.]
    turn [right v] for (450) degrees ▶
    print (drive rotation in degrees) on screen ◀ and set cursor to next row

drive velocity #

The drive velocity reporter block reports how fast the robot is driving.

It can report velocity as a percentage from -100% to 100%, or in rpm (revolutions per minute) from -127 to 127. A positive value means the robot is driving forward. A negative value means the robot is driving in reverse.

    (drive velocity in [% v])

Parameters	Description
unit	The unit to report drive velocity in: % (from -100% to 100%) or rpm (revolutions per minute, from -127 to 127).

Example

    when started
    [Display the velocity as the robot is moving.]
    drive [forward v]
    wait (1) seconds
    print (drive velocity in [% v]) on screen ◀ and set cursor to next row
    stop driving

drive current #

The drive current reporter block reports how much electrical current the drivetrain is using, measured in amps (amperes) from 0.0 to 1.2 A. Current is the amount of electricity flowing through the drivetrain.

A higher current value means the drivetrain is using more electrical current. This can happen when the robot is pushing against an object or trying to move when it is stuck.

This can be used to check if the drivetrain is struggling during a movement. If current stays high, the drivetrain may get warmer or use power less efficiently.

    (drive current in [amps v])

Parameters	Description
	This block has no parameters.

Example

    when started
    [Display the current as the robot is moving.]
    set print precision to [0.01 v] on screen
    drive [forward v]
    wait (1) seconds
    print (drive current in [amps v]) on screen ◀ and set cursor to next row
    stop driving