Some people put a 0.1uF and a larger 10-100uF on both sides of the voltage regulator. A larger cap helps guard against large droops in power (“brownouts”, like if you were turning on a relay), while the 0.1uF helps guard against noise on the power line (like if you had a motor running constantly)

In this application, the BlueSmirf also has some capacitors on it to help stabilize the power, so we just have to get the power to it “good enough”.

As I was gathering parts I noticed that your schematic says to use (2) 1uF capacitors but the pictures show you using two different ones and the notes on Flickr.com say to use (1) .1uF and (1)1-10uF. If two different ones are required can you let me know which one goes on the right and which on the left. I am no expert in electronics, although I did pass that class :) but I believe the .1uF goes on the left hand side, is this correct?

Thanks again.

If you’d like to try your hand at using VB to program the Roomba, RoombaDevTools.com made a program called SCITester that might be a good starting point. It comes with the source code. For some reason their download link is down so I put it here:
http://roombahacking.com/software/scitester.zip

You might need to change it a little bit if you’re using a newer Roomba. There’s info about those changes if you search on the net (I don’t have a newer Roomba, so I can’t test). One site that might some useful info about it, and is definitely helpful if you want to add an Arduino microcontroller board to a newer Roomba is:
http://www.netfluvia.org/layer8/?p=127

Good luck and let me know how your Roomba hacking experiences turn out. :)

Could you explain (have you already?) how to build a Bluetooth connection using this less expensive chip (half the price)?

2. I just got my Roomba yesterday and so far it has just vacuumed (I love it). I have never programmed a Roomba. My only programming skills are in VBA and a small amount of C++. Once I have built a Bluetooth connection and paired it with my computer how do I upload the code? Where can I get a compiler? What are the language options? My first ‘project’ will be to add scheduling to my 530 which I saw an article that explained how to format a numeric string to set the date and time. I assume I could write that string in notepad but how do you send it over?
Thank you in advance, your website is an amazing help and i can’t wait to get into some more advanced projects.

One issue with some of my code presented on this site is that due to the onward march of technology (Java versions, OS updates, etc.), the code might not work on some operating systems without a recompile or slight tweaking. It’s nothing major, but I’ve not had a chance to work out any of the issues since my Roomba stuff is currently in storage.

Fortunately, there’s lots of other Roomba hacks out there that build on this code or use totally different code so you can try out a bunch of different approaches to see which ones you like.

Fantastic work. I’ll be getting your book soon… I’ve just bought a Roomba 415 and would like to use my MacMINI’s bluetooth capabilities to connect to the Roomba via a RooTooth. Is it as simple as plugging in the RooTooth and then loading the appropriate software? Or are there special steps such as updating firmware, etc. on the Roomba that must be done in order for it to work. Sorry for the noob-ish question. Thanks in advance!

The BlueSmirf (along with many other Bluetooth modules) is available from Sparkfun in their Bluetooth section.

If you do get a 3.3V device you want to connect to a Roomba, there are many techniques for doing so. Sparkfun has a good interfacing tutorial that covers some common cases.

One thing I’m especially worried about is the max voltage on the data pins (p.5 in data sheet):
UART_TX V OL max=0.2V V OH min=2.8V
UART_RX V IL max=0.8V V IH min=2.1V V IH max=3.7V
UART_CTS V IL max=0.8V V IH min=2.1V V IH max=3.7V
UART_RTS V OL max=0.2V V OH min=2.8V

Roomba outputs 5V on RX & TX, right? Would that fry this bluetooth unit??

Thanks!
/David