Comments on: Build a Roomba Serial Tether

By: Alan Federman

Alan Federman — Sun, 12 Feb 2012 12:55:06 +0000

A USB bib for a Freeduino will work with no modification – only three signals are needed TXD, RXD, and GND. For a Turtlebot, you might also want to isolate the unregulated power (16v) and use it to develop a 12v supply for a Kinect. (The Freeduino bib is 1/2 the cost of a RooStick and is basically the same thing.

By: Mine

Mine — Thu, 05 Jan 2012 16:43:24 +0000

Thanks for quick reply,
My Roomba model is 4150. But I don’t think the problem is the baud rate. I have one small favor to ask. Since I don’t have any experience on java programming, I couldn’t understand the explanations on roombacomm completely. I don’t even know what RXTX is. If it isn’t much of a burden, can you tell me exactly which of the three files to download from your site and which application to use in order to control roomba from Windows xp pc and any other software I require to make it work?
Thanks for your help,
Mine

By: todbot

todbot — Thu, 05 Jan 2012 05:10:28 +0000

Hi Mine,
What model Roomba do you have? The newer ones operate at 115200 instead of 57600 bps.

How did you install RXTX? (The easiest way I’ve found is to steal the one out of the Arduino software) Normally minor RXTX version mismatches aren’t an issue, but I’m not sure i’ve seen a 2.2pro1 before.

By: Mine

Mine — Wed, 04 Jan 2012 18:40:14 +0000

Hello. I built the Roomba serial interface tether as you’ve explained in your book. Echo test worked well. And I pluged the Roomba serial interface tether into the Roomba. I double click RoombaCommTest option and I select the correct port. However, I see in the display ” No Roomba. :( Is it turned on? ”
Also I have one warning:
Warning: RXTX Version mismatch
Jar version=RXTX-2.2pro1
native lib Version=RXTX-2.1-7
I installed Java my computer and Roomba model is 4150.
How we can solve this problem? Please help me. Thank you.

By: todbot

todbot — Thu, 20 Oct 2011 03:18:23 +0000

Hi Bratan, Schlem,
The socket is the socket on the Roomba, which the mini DIN 8-pin cable plugs in to. The 10uF capacitor I reference is C2 or C3 (the ones on the 5V power supply). The actual value can be between 1uF and 100uF. The capacitor values around the MAX232 are correct.

By: todbot

todbot — Thu, 20 Oct 2011 03:13:18 +0000

Hi Israel,
The iRobot USB-Serial cable should come with instructions on how to install drivers for it. Once you install the drivers, the cable will show up as a serial port with the name “/dev/tty.usbserial…” or “/dev/tty.usbmodem…”. It’s this name that will replace the “/dev/cu.KeySerial1″ that is in my example.

By: Israel Alvarez

Israel Alvarez — Thu, 20 Oct 2011 02:16:48 +0000

I have a Roomba Discovery 4210 and I’ve purchased the iRobot USB-Serial cable. I’ve downloaded the various processing tools and have them running in GUI test mode on a Lion MacBook. My problem is actual communication with the Roomba: the /dev/cu.KeySerial1 device doesn’t exist on my machine, and I’m not sure which device to point the serial communications to: obviously the cu.Blue* devices aren’t appropriate. Any thoughts?

By: Bratan

Bratan — Fri, 29 Jul 2011 17:07:58 +0000

With regards to 10uF capacitor, I’m also as confused as Schlem. No mentioning of it in the part list of schematic, but then out of nowhere it comes up in the description in the book. Also I noticed that Mini DIN 8-pin socket is not used anywhere. I guess there was no need to cut perfect good cable? :)

By: schlem

schlem — Fri, 28 Jan 2011 08:22:21 +0000

Just to follow up on my comment: I did some research on the MAX232 chip and it turns out that the chip outputs +/- 8.5 V on pins 2 and 6 respectively. Who knew? In this context, the schematic shows the negative Cap leads connecting to a “more negative” source. My ignorance.

As regards the 10uF cap – the data sheet (for my flavor max232) makes no mention of this, spec’ing 1.0uF caps, but allowing 0.1uF caps as acceptable.

I still can’t believe that I am the only person with these questions. Maybe I know just enough to be dangerous. Maybe other people are better at answering their questions before whining on the comment board.

Thanks for humoring me, regards,
Schlem

By: schlem

schlem — Fri, 28 Jan 2011 07:12:53 +0000

Hi
Great book. Itching to hack my Roombas. In my hurried enthusiasm, I rushed out and bought a Rootooth, and it won’t even pair with any of my computers or Droids. :(

So, I rolled it back to square one to build a simple serial interface, procured the necessary parts, and now I am confused. I am a late-comer, so I read all the errata/comments, and I can’t believe nobody has these questions:

-Pinout orientation for mini-din7/8 is well documented. Pinout orientation for DB-9 not so much. Is it looking at the connector from the connection side or the wire side?

-Discussion of parts in fig 3-6 references a 10uF cap not mentioned in the parts list nor the schematic. Either way you use 6 caps, but which one is the 10uF? Does it even really matter?

-The two 1.0uF caps connected to pins 2 and 6 appear to be polarized backwards (+ to – and vice versa). I hear that electrolytics blow up when hooked up wrong. I’m no Electrical Engineer – am I misunderstanding something here?

I agree that Radio Shack part no. 276-150 is the best thing they sell! 417 wonderful little holes.
-schlem