Actuator Commands - iRobot CREATE - OPEN INTERFACE Manual

Actuator Commands

The following commands control iRobot Create's actuators:
wheels, speaker, LEDS, digital outputs and low side
driver outputs.
Drive Opcode: 137
This command controls Create's drive wheels. It takes four
data bytes, interpreted as two 16-bit signed values using
two's complement. The first two bytes specify the average
velocity of the drive wheels in millimeters per second
(mm/s), with the high byte being sent first. The next two
bytes specify the radius in millimeters at which Create will
turn. The longer radii make Create drive straighter, while
the shorter radii make Create turn more. The radius is
measured from the center of the turning circle to the center
of Create. A Drive command with a positive velocity and a
positive radius makes Create drive forward while turning
toward the left. A negative radius makes Create turn toward
the right. Special cases for the radius make Create turn
in place or drive straight, as specified below. A negative
velocity makes Create drive backward.
NOTE: Internal and environmental restrictions may prevent
Create from accurately carrying out some drive commands.
For example, it may not be possible for Create to drive at
full speed in an arc with a large radius of curvature.
• Serial sequence: [137] [Velocity high byte] [Velocity low byte]
[Radius high byte] [Radius low byte]
• Available in modes: Safe or Full
• Changes mode to: No Change
• Drive data byte 1: Velocity (-500 – 500 mm/s)
• Drive data byte 2: Radius (-2000 – 2000 mm)
Special cases:
Straight = 32768 or 32767 = hex 8000 or 7FFF
Turn in place clockwise = hex FFFF
Turn in place counter-clockwise = hex 0001
Example:
To drive in reverse at a velocity of -200 mm/s while
turning at a radius of 500mm, send the following serial
byte sequence:
[137] [255] [56] [1] [244]
Velocity = -200 = hex FF38 = [hex FF] [hex 38] = [255] [56]
Radius = 500 = hex 01F4 = [hex 01] [hex F4] = [1] [244]
iRobot Create Open Interface (OI) Specification
Drive Direct
This command lets you control the forward and backward
motion of Create's drive wheels independently. It takes
four data bytes, which are interpreted as two 16-bit signed
values using two's complement. The first two bytes specify
the velocity of the right wheel in millimeters per second
Data Bytes: 4
(mm/s), with the high byte sent first. The next two bytes
specify the velocity of the left wheel, in the same format.
A positive velocity makes that wheel drive forward, while a
negative velocity makes it drive backward.
• Serial sequence: [145] [Right velocity high byte]
[Right velocity low byte] [Left velocity high byte]
[Left velocity low byte]
• Available in modes: Safe or Full
• Changes mode to: No Change
• Drive Direct data byte 1: Right wheel velocity
(-500 – 500 mm/s)
• Drive Direct data byte 1: Left wheel velocity
(-500 – 500 mm/s)
LEDs
This command controls the LEDs on Create. The state of
the Play and Advance LEDs is specified by two bits in the
first data byte. The power LED is specified by two data
bytes: one for the color and the other for the intensity.
• Serial sequence: [139] [LED Bits] [Power Color]
[Power Intensity]
• Available in modes: Safe or Full
• Changes mode to: No Change
• LEDs data byte 1: LED Bits (0 – 10)
Advance and Play use green LEDs. 0 = off, 1 = on
Bit
LED
Power uses a bicolor (red/green) LED. The intensity and
color of this LED can be controlled with 8-bit resolution.
• LEDs data byte 2: Power LED Color (0 – 255)
0 = green, 255 = red. Intermediate values are
intermediate colors (orange, yellow, etc).
• LEDs data byte 3: Power LED Intensity (0 – 255)
0 = off, 255 = full intensity. Intermediate values are
intermediate intensities.
Example:
To turn on the Advance LED and light the Power LED green
at half intensity, send the serial byte sequence [139] [8]
[0] [128].
Opcode: 145
Opcode: 139
7 6 5 4
n/a n/a n/a n/a Advance
Data Bytes: 4
Data Bytes: 3
3 2 1 0
n/a Play n/a
9