iRobot CREATE - OPEN INTERFACE Manual page 10

Digital Outputs Opcode: 147
This command controls the state of the 3 digital output
pins on the 25 pin Cargo Bay Connector. The digital outputs
can provide up to 20 mA of current.
• Serial sequence: [147] [Output Bits]
• Available in modes: Safe or Full
• Changes mode to: No Change
• Digital Outputs data byte 1: Output Bits (0 –7);
0 = low (0V); 1 = high (5V).
Example schematics
+5V
Visible LED
470 Ohms
DIGITAL_OUTPUT
Warning: When the Robot is switched ON, the Digital
Outputs are High for the first 3 seconds during the
initialization of the bootloader
Bit 7 6 5 4 3
Output
PWM Low Side Drivers Opcode: 144
This command lets you control the three low side drivers
with variable power. With each data byte, you specify the
PWM duty cycle for the low side driver (max 128). For
example, if you want to control a driver with 25% of battery
voltage, choose a duty cycle of 128 * 25% = 32.
• Serial sequence: [144] [Low Side Driver 2 Duty Cycle]
[Low Side Driver 1 Duty Cycle] [Low Side Driver 0 Duty Cycle]
• Available in modes: Safe or Full
• Changes mode to: No Change
• Low Side Drivers data byte 1: Duty cycle for low side
driver 2 (0 - 128)
• Low Side Drivers data byte 2: Duty cycle for low side
driver 1 (0 - 128)
• Low Side Drivers data byte 3: Duty cycle for low side
driver 0 (0 - 128)
iRobot Create Open Interface (OI) Specification
Data Bytes: 1
SWITCHED_VPWR
1N4001 DC MOTOR
1K Ohms
ANALOG_OUTPUT
S8050
2 1
digital-out-2 digital-out-1 digital-out-0
(pin 20) (pin 7) (pin 19)
Data Bytes: 3
Example:
To turn on low side driver 2 at 25% and low side driver 0 at
100%, send the serial byte sequence [144][32][0][128]
Low Side Drivers
This command lets you control the three low side drivers. The
state of each driver is specified by one bit in the data byte.
Low side drivers 0 and 1 can provide up to 0.5A of current.
Low side driver 2 can provide up to 1.5 A of current. If too
much current is requested, the current is limited and the
overcurrent flag is set (sensor packet 14).
• Serial sequence: [138] [Driver Bits]
• Available in modes: Safe or Full
• Changes mode to: No Change
• Low Side Drivers data byte 1: Driver bits (0 – 7)
Example schematic
0
0 = off, 1 = on at 100% PWM duty cycle
Bit 7
Output
Example:
To turn on only low side driver 1, send the serial byte
sequence [138] [2].
Note: Speed control of motors uses the PWM Low Side
Drivers Command. This command exists for Backward
compatibility with the Roomba OI.
Opcode: 138
SWITCHED_VPWR
DC MOTOR
LD1
6 5 4 3 2
Low Side
Side Driver
2 (pin 24)
Data Bytes: 1
1 0
Low Side
Driver 1 Driver 0
(pin 22) (pin 23)
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