We're the happy owners of a Roomba 620.

It's really doing a great job, but a scheduling feature is lacking, which means that we always had to trigger the cleaning process manually.

Fortunately, the iRobot Open Interface allows for easy programming. There are numerous ways of communicating with a Roomba. Here, we'll be using an Arduino, which is probably the easiest / cheapest way to do it.

Basically, the Arduino will act as a bridge between the computer and the robot, allowing us to send scheduling commands.

Step 1: What You Need

A Roomba (I am using a 600 series model)
An Arduino Uno and its USB cable (any other model should do the job as well)
A computer
4 wires

And that's it.

Step 2: Remove Roomba's Cover

The Open Interface port should now be visible.

Step 3: Plug!

Using the wires, connect the Arduino to the Roomba as follows:

Roomba port 7 (GND) <-> Arduino GND
Roomba port 3 (RXD) <-> Arduino D4
Roomba port 4 (TXD) <-> Arduino D3
Roomba port 5 (BRC) <-> Arduino D5

The ground (GND) should be connected first and disconnected last, it's safer (for the Arduino).

Note: Don't connect the Roomba ports 1-2 to the Arduino, their voltage might damage your board!

Step 4: Programming Time

Connect the USB cable between the Arduino and the computer.

Start the Arduino software (freely available here).

Set the port using the menu Tools > Port > Arduino Uno (or whichever board you're using).

Open the serial monitor and select 19200 bauds.

Copy the following program:

// Roomba Scheduler

// Roomba port 7 (GND) onto Arduino GND
// Roomba port 3 (RXD) onto Arduino D4
// Roomba port 4 (TXD) onto Arduino D3
// Roomba port 5 (BRC) onto Arduino D5

#include <SoftwareSerial.h>

int rxPin = 3 ;
int txPin = 4 ;
int ddPin = 5 ;
int ledPin = 13 ;

SoftwareSerial Roomba(rxPin, txPin) ;

void setup()
{

  // Arduino pins setup

  pinMode(ddPin,  OUTPUT) ;
  pinMode(ledPin, OUTPUT) ;

  digitalWrite(ledPin, HIGH) ;
  digitalWrite(ddPin, LOW) ;

  delay(2000) ;

  // Changing Roomba baud rate to 19200

  digitalWrite(ddPin, HIGH) ;
  delay(100) ;
  digitalWrite(ddPin, LOW) ;
  delay(200) ;
  digitalWrite(ddPin, HIGH) ;
  delay(100) ;
  digitalWrite(ddPin, LOW) ;
  delay(200) ;
  digitalWrite(ddPin, HIGH) ;
  delay(100) ;
  digitalWrite(ddPin, LOW) ;
  delay(200) ;
  digitalWrite(ddPin, HIGH) ;
  delay(100) ;

  // Serial communication setup

  Serial.begin(19200) ;
  Roomba.begin(19200) ;

  // Roomba Open Interface setup

  Serial.println("Roomba Open Interface setup...") ;
  delay (1000) ;

  Roomba.write(128) ;  // START
  delay(150) ;
  Serial.println("Sending Safe Mode command...") ;
  delay (1000) ;

  Roomba.write(131) ;  // CONTROL
  delay(150) ;
  digitalWrite(ledPin, LOW) ;
  delay (500) ;

  // Sing a song

  sing() ;

  // Set current time

  setCurrentTime(2, 13, 42) ;

  // Set schedule

  setSchedule() ;

  // Finishing

  Serial.println("Roomba Open Interface stopping...") ;

  Roomba.write((byte)173) ; // Stop the OI

  Serial.println ("All Done Baby!") ;

}

void loop()
{

}

void sing ()
{

  Serial.println("Singing...") ;

  Roomba.write((byte)140) ;
  Roomba.write((byte)0) ;
  Roomba.write((byte)7) ;
  delay(500) ;

  Roomba.write((byte)76) ;
  Roomba.write((byte)16) ;
  Roomba.write((byte)76) ;
  Roomba.write((byte)32) ;
  Roomba.write((byte)79) ;
  Roomba.write((byte)16) ;
  Roomba.write((byte)79) ;
  Roomba.write((byte)16) ;
  Roomba.write((byte)77) ;
  Roomba.write((byte)16) ;
  Roomba.write((byte)74) ;
  Roomba.write((byte)16) ;
  Roomba.write((byte)72) ;
  Roomba.write((byte)32) ;
  delay(500) ;

  Roomba.write((byte)141) ;
  delay(50) ;
  Roomba.write((byte)0) ;
  delay(50) ;

  delay(500) ;

  Serial.println("Singing [OK]") ;

}

void setCurrentTime (int aDayOfWeek, int anHourCount, int aMinuteCount)
{

  Serial.println("Setting current time...") ;

  Roomba.write((byte)168) ; // Command code
  Roomba.write((byte)aDayOfWeek) ; // Day (0: Sunday, 1: Monday, 2:Tuesday, 3:Wednesday, 4: Thursday, 5: Friday, 6: Saturday)
  Roomba.write((byte)anHourCount) ; // Hour
  Roomba.write((byte)aMinuteCount) ; // Minute

  delay(500) ;

  Serial.println("Setting current time [OK]") ;

}

void setSchedule ()
{

  Serial.println("Setting schedule...") ;

  Roomba.write((byte)167) ; // Command code
  Roomba.write((byte)127) ; // Days (127 (dec) = 01111111 (binary) = 0(Sat)(Fri)(Thu)(Wed)(Tue)(Mon)(Sun) -> schedule everyday)
  Roomba.write((byte)16) ; // Sunday Hour
  Roomba.write((byte)45) ; // Sunday Minute
  Roomba.write((byte)15) ; // Monday Hour
  Roomba.write((byte)0) ; // Monday Minute
  Roomba.write((byte)15) ; // Tuesday Hour
  Roomba.write((byte)0) ; // Tuesday Minute
  Roomba.write((byte)15) ; // Wednesday Hour
  Roomba.write((byte)0) ; // Wednesday Minute
  Roomba.write((byte)15) ; // Thursday Hour
  Roomba.write((byte)0) ; // Thursday Minute
  Roomba.write((byte)15) ; // Friday Hour
  Roomba.write((byte)0) ; // Friday Minute
  Roomba.write((byte)15) ; // Saturday Hour
  Roomba.write((byte)0) ; // Saturday Minute

  delay(500) ;

  Serial.println("Setting schedule [OK]") ;

}

Step 5: Adjust Your Parameters

You have to adjust the following parameters in the code:

Set the current time: (Day, Hour, Minute)

setCurrentTime(2, 13, 42) ;

Set the desired schedule:

Roomba.write((byte)127) ; // Days (127 (decimal) = 1111111 (binary) = (Sat)(Fri)(Thu)(Wed)(Tue)(Mon)(Sun) -> schedule everyday)
  Roomba.write((byte)16) ; // Sunday Hour
  Roomba.write((byte)45) ; // Sunday Minute
  Roomba.write((byte)15) ; // Monday Hour
  Roomba.write((byte)0) ; // Monday Minute
  Roomba.write((byte)15) ; // Tuesday Hour
  Roomba.write((byte)0) ; // Tuesday Minute
  Roomba.write((byte)15) ; // Wednesday Hour
  Roomba.write((byte)0) ; // Wednesday Minute
  Roomba.write((byte)15) ; // Thursday Hour
  Roomba.write((byte)0) ; // Thursday Minute
  Roomba.write((byte)15) ; // Friday Hour
  Roomba.write((byte)0) ; // Friday Minute
  Roomba.write((byte)15) ; // Saturday Hour
  Roomba.write((byte)0) ; // Saturday Minute

Step 6: Let's Go!

Click the arrow button to execute your program.

It should take a couple of seconds. Check the monitor, the following text should appear:

Roomba Open Interface setup...
Sending Safe Mode command...
Singing...
Singing [OK]
Setting current time...
Setting current time [OK]
Setting schedule...
Setting schedule [OK]
Roomba Open Interface stopping...
All Done Baby!

If everything goes smooth, Roomba will sing a cool song.

You're done! Just unplug and put the lid back.

Congrats!