Pistreaming Roomba

The final product: Raspberry Pi mounted on Roomba

Screenshot from web browser, displaying Pistreaming Roomba's video and control buttons

Hardware

• A Roomba supporting the iRobot Open Interface (mine is a 655)
  
• Raspberry Pi equipped with wifi and a USB-A port (I used a model 3B)
  
• Raspberry Pi camera
• USB-to-TTL adapter
  
• 7 pin Mini-DIN connector
• 5V voltage regulator
  
• Micro USB male connector (I just cut a cable I had on hand)
• JST-PH connector male-female pair

Talking with Roomba

iRobot, the maker of Roomba, seem to be very open to the idea of their products being used for academic or "hacker" projects.  They provide a serial API, the Open Interface, which makes it very easy to control from your own microcontroller.  And the DIN connector used to interface with the Roomba is present on nearly all models.

The DIN connector spec

Some key notes about the DIN connector, with respect to connecting a Raspberry Pi:

• The Vpwr is the Roomba's battery voltage.  For my Roomba, I measured this at around 13V.  The Pi requires either 5V or 3.3V power.  I decided to power the pi via the micro USB port, which wants 5V.  To get there, I put a voltage regulator in between the Roomba's 13V and the micro USB powering the Pi.
• If you'd rather, you could always power the Pi from an external source, such as a USB power bank.  Then you wouldn't need a voltage regulator or Roomba's power at all.
• The serial (RXD, TXD) logic levels coming out of the Roomba are 5V, whereas the Pi's logic level is 3.3V.  Now, the Pi's 3.3V signals should be readable by the Roomba.  But, the reverse isn't true -- the Roomba's 5V logic could damage the Pi's 3.3V pins.  I figured a good way around this would be to use a USB-to-TTL adapter which accepts 5V logic levels.
  
• It may be possible to only wire up the Pi-to-Roomba serial connection (Pi's TX to Roomba's RX), then you probably wouldn't need to worry about logic levels, since usually 5V logic level circuits will read 3.3V logic levels just fine.  In this case you wouldn't need the USB-to-TTL adapter; just wire directly to the Pi's TX UART pin.  I haven't test this, however.

Once you have the TX and RX wired up, there are several easy-to-use libraries available on github (and probably elsewhere) for communicating using the Open Interface.  I found a Python based library called PyRoombaAdapter which worked out well for me, and so is used in this project.

Remote Power-On

One thing I noticed in my initial testing with controlling Roomba with the Open Interface is that it's possible for Roomba to be in a Power Off state.  In this state, it isn't listening on the Open Interface and so won't respond to any commands from the Pi.  It enters this state after a period of time doing nothing (probably to save battery life) or it can be manually triggered over the Open Interface.  (It doesn't appear to enter this state while sitting at its charging dock, however.)  The only way to power Roomba back on is to press its "Clean" button.

For my project, I wanted to be able to fully control Roomba, including power on.  So, I added some extra wiring to trigger the "Clean" button push.  After i pulled off my Roomba' cover, I noted that the button in question, marked "SW5", functioned by momentarily connecting the contact points on either side.  One side is battery voltage (13V) and the other side is usually ground.

Roomba under the hood

Fortunately, I found that the SW5 button will trigger even if momentarily hit with a voltage much smaller than 13V -- in fact 3.3V from one of the Pi's GPIO pins will work.  So, I soldered a wire from the SW5 button to a JST-PH female connector which I hot-glued just above the DIN connector.  (It would have been much slicker to utilize one of the other port on the DIN connector for this - for instance, there are two power outs and two grounds, where you only really need one of each.  But this would require desoldering the DIN connector from the Roomba board ... I didn't have a spare and was concerned about screwing it up, so did it with a new connector all together.)

Roomba "Clean" button trigger wire

Before putting Roomba' cover back on, I cut out a hole for the connectors.  I drilled a 1/2" hole for the DIN connector, then carved out a hole for the JST-PH with a Dremel.

Hole in Roomba cover

The only other Roomba modification I made was to add a strip of velcro to attach the Pi.  The modifications I did don't prevent Roomba from being used normally.

Wiring closeup

The only other thing to note is the extra, short green wire I added to the unused port of the JST-PH connector.  I added this just to help when pushing it in and pulling it out.  It's kind of far down there!

Pi Connections

Connecting to the Pi is fairly straightforward. 

Power the pi via the Micro USB cable (which you'll need to attach to the 5V output and ground of the 5V voltage regulator). 

Plug in the USB-to-TTL adapter to the Pi's USB port.  My USB-to-TTL adapter had a jumper to select either 3.3V or 5V logic; set it to 5V.  Make sure you connect the adapter's RX to Roomba's TX, and adapter's TX to Roomba's RX.

For the "Clean" button trigger, connect to a GPIO pin which is normally low.  I believe you can set this up for any GPIO pin, but I just checked one that was already low by default, GPIO 18.  The software will momentarily set this pin high (3.3V) and then low again, which triggers a button push response from Roomba.

Software

See the github's Readme for a full description of the software.  I started with the Pistreaming project, then added on Roomba control stuff.

For extra credit, sign up for a dynamic DNS service (like No-ip) and set up port forwarding on your router for ssh (usually port 22) and pistreaming's http server and websocket server (8082 and 8084 in the default code).  Now you have a Roomba equipped with streaming video which you can control over the internet!  Go ahead and have some strangers vacuum up your house!