Serial port connection and configuration
By Anna Sandler
iRobot has developed a Serial port Command Interface (SCI) – an API
for communication with Roomba.
The interface is bidirectional, and is being sent through Roomba’s serial
port which is located here.
There are two ways to connect your program/app with Roomba:
- Using a Bluetooth device (recommended)- like RooTooth the price is ~100$.
- Or using "USB to serial" cable like this the price is ~30$.
RooTooth, a bluetooth device for Roomba
USB to serial port cable
Finding the right connection speed
Baud rate is the number of bits per second that are being transmitted.
Roomba's default baud rate vary by the version of your Roomba:
- Create, Roomba 4XX series and Dirt dog are using 57,600
baud rate by default.
- Roomba 5XX and 7XX series are using 115,200 baud rate by default.
Connecting with Serial-to-USB cable
If you choose the USB to serial cable, be aware that you are limited
to a computer based programs (smart phones can’t accept USB cables (yet)), and the
cable limits Roomba movement.
In order to start using the serial cable, please install the drivers
from the installation disc that came with your cable.
Whether you use code (.NET or Java or C++) or a terminal software
to send commands, make sure you initialize the serial port object, or configure the terminal with
the correct baud rate according to your Roomba model as mentioned above.
That's it! We are ready to send some commands!
Skip to: "How to send commands to Roomba" chapter
Connecting with Bluetooth
How to pair Roomba with Bluetooth device to smartphone or computer
If you've decided to go with the recommended Bluetooth-based option, all
you need to do is to turn on Bluetooth< on your smartphone or computer, and pair the Bluetooth device with the it.
Note that some of the computers don't have Bluetooth support (usually desktops).
In this case, you can use a Bluetooth dongle.
and voile’ your computer now supports Bluetooth connections.
After you've enabled Bluetooth on the computer that is going to run the program/app, just pair the device with your computer.
If you use a PC, open Bluetooth devices -> add a device -> select the Bluetooth device -> enter the pin code (typically 1234),
and you are paired!
Why the configuration of a baud rate is ignored
If you are using a Bluetooth device, things are a bit more complicated than with a cable.
There are two transmission zones:
- First zone: (Computer to Bluetooth) - from a computer/smartphone to the Bluetooth device,
- Second zone: (Bluetooth to Roomba) - from a Bluetooth device to the Roomba.
The baud rate of the first zone (Computer-Bluetooth) is set automatically
during the pairing process between your computer/smartphone and the Bluetooth
device;
The second zone- between the Bluetooth device and a Roomba
must be configured.
Note that the Bluetooth device is a virtual serial-port, and the baud
rate between the computer and the Bluetooth device (the first
zone) is being selected during the handshake with the computer.
Thus the value that is specified as a baud rate in the terminal software’s
connection window, or from the serial port initialization in your
code, is ignored. (The Bluetooth driver is handling the connection speed
for us, we only need to configure the second zone), so just make sure your device
is connected and you are using the right port to send these commands.
How to configure a Bluetooth device to support the correct Roomba's baud rate
The baud rates on the sender and receiver must be identical.
In case the baud rates are not aligned between your Bluetooth device and your Roomba
model, (the second zone) you will need to change the defaults on your Bluetooth
device to match the baud rate of your Roomba.
Some of the RooTooth devices are configured with 57,600 baud rate as a default,
while others are using the 115,200 default baud rate.
If you are not sure about the default baud rate of your Bluetooth device, you can
check it by sending the following commands to your Bluetooth device using terminal
software like RealTerm, or using a code to send those commands.
(Press the "Enter" at the end of each command if you are using a terminal, or add the '\n' character if you are using a code).
RooTooth configuration status
Explanation:
- [$$$] command is used to enter the configuration mode of your Bluetooth device;
- [D] command is used to DISPLAY Bluetooth device's settings;
- [---] command is used to exit Bluetooth device's configuration mode;
Baud rate values can be (Baudrt):
9,600, 57.6 for 57600 baud rate or 115K for 115,200
baud rate.
By default there is a 60-seconds configuration timeout after which no changes are allowed.
The following commands will remove the timeout (change the timeout to be infinite):
After changing the timeout, Rootooth is ready for the baud rate changes.
In order to change the baud rate permanently (for zone 2), send the following commands:
(Press the "Enter" at the end of each command if you are using a terminal, or add the '\n' character if you are using a code).
Explanation:
- [$$$] command is used to enter the configuration mode of your Bluetooth device;
- [SU,57.6] for Roomba 4XX, Create and Dirt dog
or [SU, 115k] for Roomba 5XX or 7XX
models.
This command will permanently change the baud rate value in the Bluetooth device's settings.
- [R,1] command is used to restart the device in order for the changes to take affect;
In order to change a baud rate temporarily, send the following commands:
(Press the "Enter" at the end of each command if you are using a terminal, or add the '\n' character if you are using a code).
Explanation:
- [$$$] command is used to enter the configuration mode of your Bluetooth device;
- [U,57.6,N] for Roomba 4XX, Create or Dirt dog,
[U,115k,N] for Roomba 5XX or 7XX
models.
This command will change the baud rate and exit the command mode, but will
not change the baud rate saved on the flash memory (you won't be able to see
the new values when you use the command [D])
On next Bluetooth device restart,
the value will be changed again to its previous value.
When changing Bluetooth device configuration from code (.NET/Java..), a delay of
at least 100 milliseconds must pass between commands (not including the New Line character
that is added to the end of each command ['\n']). The delay is relevant for all commands
except the first command [$$$].
What's next?
Let's move forward and learn
how to send commands to Roomba
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