Friday, May 31, 2013

Encoder Fixed

 Naughty little wheel encoder!
I mentioned suspicious signals from the encoders. Here's what I was seeing. This is a plot of the distance traveled versus time. The plot is showing that one of the wheels is able to travel more than 300m in a fraction of a second. Cool.

Thursday, May 30, 2013

AVC Update

Over on diyrovers Google Group we've been getting some sneak peeks at the 2013 AVC competitors' progress!

Team 0x27, winners of last  year's AVC posted up a video of preliminary testing of their unicycle robot...

Meanwhile, Savage Solder, a recent Robomagellan champ, is performing brilliantly in this test video:

Thursday, May 23, 2013

GPS Noise Isolation Part 2

Experimental opto-isolator board on Data Bus
I'm now using a opto-isolators on my GPS to mbed connection, a much better solution than the chokes I used to stamp out RF interference previously.

Tuesday, May 21, 2013

Data Bus Baseboard on Tindie

Data Bus mbed baseboards are now available on Tindie as a fundraiser!

Now you can build your own autonomous rover! This board is the fifth revision of the board that's been powering my AVC-podium-placing rover, Data Bus, the last few years.

If you want to experiment with your own algorithms on a powerful 96MHz ARM processor and want a head start on building their 2014 AVC ground vehicle entry, well, here you go!

  • Three UART ports, one 3.3V, two 5V, series resistor protection
  • Five I2C ports, all 3.3V
  • ESC and steering Servo connector
  • Dual wheel encoder port
  • Onboard 5V regulator powered by ESC 6V BEC powers 5V UARTs
  • Separate mbed supply rail to keep noise out of your GPS.
  • Filtering / bypass caps

Just get an mbed, load it up with my code, add an L3G4200D gyro, Venus or uBlox GPS, wheel encoders.

Data Bus source code repository
AVC2012 code on

Friday, May 17, 2013

Noise and the 3DR uBlox LEA-6 GPS

3DR uBlox LEA-6 GPS + secret sauce
I'm evaluating a 3DR uBlox LEA-6 GPS for use on Data Bus to either replace or supplement its current module, the Venus 638FLPX.

At first the GPS could not obtain a fix. Here's how I brought the GPS from no fix to a 10-satellite fix. From my basement!

Tuesday, May 14, 2013

Ramp Jump Breaks Data Bus

I built a ramp very similar to the one for the 2013 AVC so I could get a sense of how the robot will handle the jumps.

Unfortunately I stripped out one of the plastic idler gears doing a high speed jump. I've got a metal set on order to arrive Friday.

Can you see the stripped teeth on the small idler gear?
I was hoping to test my revised path following algorithm. That'll have to wait until I replace the gear set. More on the path following algorithm soon.

Just under four weeks left.

Thursday, May 9, 2013

Reverse Engineering GM ECMs

This is the tale of how I wrote a Perl disassembler for the Motorola 6801 CPU to learn how the fuel injection computer that I installed onto my Jeep works.

Almost 200 pages of source code and data create code to run late-80's GM fuel injected engines. DIYers retrieved machine code, disassembled it, and reverse engineered code and hundreds of parameters 15 years ago.

Complete ASDZ Source for 1227747 (pdf)

Wednesday, May 8, 2013

2013 Sparkfun AVC Entry Video

Here's a demo of Data Bus driving itself around in the rain outside my house. Sparkfun requires a demo submitted before the May 8 deadline. I actually submitted it on the afternoon of May 8, so I hope I'm not too late.

Data Bus is configured to travel slowly, around 6 m/s, between four waypoints outside my house. I ran it a few times and it seemed to traverse approximately the same route each time.

With only a month left, I guess I can stop procrastinating, now. I'd like to at least get a sense of how accurately I can control its path and make a few improvements before June 8.

Wednesday, May 1, 2013

Taking Time Off

I am taking time off posting for the next couple weeks due to personal reasons. Last week I was too focused on fuel injection tuning for my Jeep to work on robotics or write articles.