Page 437 - Hacking Roomba

418 Appendix C — iRobot Roomba Open Interface (ROI) Specification

iRobot® Roomba® Open Interface (ROI) Specification
Roomba Open Interface Overview Serial Port Settings
Versions of iRobot® Roomba® Vacuuming Robot manufactured Baud: 57600 or 19200 (see below)
after October, 2005 contain an electronic and software interface Data bits: 8
that allows you to control or modify Roomba’s behavior and Parity: None
remotely monitor its sensors. This interface is called the iRobot Stop bits: 1
Roomba Open Interface or iRobot ROI. Flow control: None
iRobot ROI is a serial protocol that allows users to control a By default, Roomba communicates at 57600 baud. If you are
Roomba through its external serial port (Mini-DIN connector). using a microcontroller that does not support 57600 baud, there
The ROI includes commands to control all of Roomba’s actuators are two ways to force Roomba to switch to 19200:
(motors, LEDs, and speaker) and also to request sensor data
from all of Roomba’s sensors. Using the ROI, users can add METHOD 1:
functionality to the normal Roomba behavior or they can create
completely new operating instructions for Roomba. When manually powering on Roomba, hold down the power
button. After 5 seconds, Roomba will start beeping. After
10 seconds, Roomba will play a tune of descending pitches.
Roomba will now communicate at 19200 baud until the battery
Physical Connections is removed and reinserted (or the battery voltage falls below the
minimum required for processor operation) or the baud rate is
explicitly changed via the ROI.
To use the ROI, a processor capable of generating serial
commands such as a PC or a microcontroller must be connected
to the external Mini-DIN connector on Roomba. The Mini-DIN METHOD 2:
connector provides two way serial communication at TTL Levels You can use the Device Detect to change Roomba’s baud
as well as a Device Detect input line that can be used to wake rate. After you have awakened Roomba (using Device Detect
Roomba from sleep. The connector also provides an unregulated or by some other method) wait 2 seconds and then pulse the
direct connection to Roomba’s battery which users can use to Device Detect low three times. Each pulse should last between
power their ROI applications. The connector is located in the rear 50 and 500 milliseconds. Roomba will now communicate at
right side of Roomba beneath a snap-away plastic guard.
19200 baud until the battery is removed and reinserted (or the
battery voltage falls below the minimum required for processor
ROOMBA’S EXTERNAL SERIAL PORT operation) or the baud rate is explicitly changed via the ROI.
MINI-DIN CONNECTOR PINOUT
Here is a Python code fragment that illustrates this method
This diagram shows the pin-out of the top view of the female (Device Detect is connected to the PC’s RTS line via a level
connector in Roomba. Note that pins 5, 6, and 7 are towards the shifter):
outside circumference of Roomba.
6 ser = serial.Serial(0, baudrate=19200,
timeout=0.1)
ser.open()
7 5
# wake up robot
ser.setRTS (0)
4 3
time.sleep (0.1)
ser.setRTS (1)
2 1 time.sleep (2)
# pulse device-detect three times
for i in range (3):
Pin Name Description
ser.setRTS (0)
1 Vpwr Roomba battery + (unregulated) time.sleep (0.25)
2 Vpwr Roomba battery + (unregulated) ser.setRTS (1)
time.sleep (0.25)
3 RXD 0 – 5V Serial input to Roomba
4 TXD 0 – 5V Serial output from Roomba
5 DD Device Detect input (active low) – used to wake up
Roomba from sleep
6 GND Roomba battery ground
7 GND Roomba battery ground
The RXD, TXD, and Device Detect pins use 0 – 5V logic, so
a level shifter such as a MAX232 chip will be needed to
communicate with a Roomba from a PC, which uses rs232
levels.
2 www.irobot.com