Using a different gyro on a turtlebot

asked 2011-06-29 03:30:14 -0500

Alaina
121 ●4 ●6 ●12 http://9thsense.com/

updated 2011-06-29 05:47:50 -0500

tfoote

58457 ●128 ●550 ●526 http://www.ros.org/

Hi folks,

We are building our own TurtleBot and I am having problems with the IMU.

I am using the SparkFun ADXL203/ADXRS613 IMU (SEN-09127, http://bit.ly/jw6iUL ).

What I am experiencing when I try to calibrate it is similar to the problem described at: http://answers.ros.org/question/1333/...

[INFO] [WallTime: 1308820084.864965] Estimating imu drift
[INFO] [WallTime: 1308820085.165909] Still waiting for imu
[INFO] [WallTime: 1308820085.466922] Still waiting for imu
[INFO] [WallTime: 1308820085.767989] Still waiting for imu

...but I haven't remapped anything.

The IMU is wired to +5V, ground and AIN on the Create through the pinouts on an Element Direct BAM ( http://bit.ly/iHaTB8 ). The BAM isn't the problem; AIN passes through to pin 4, just like it should. When I first saw the problem I wired the IMU up to +5V on a bench supply and slapped a multimeter between RATE and ground. When I move the IMU around, I can see the voltage change, so the IMU is working.

If I look at /imu/raw and move the Create around manually, the X/Y/Z values remain at 0 (I don't have the accelerometer pins connected to anything, FYI), so I know that the problem is somewhere between the IMU and the ROS gyro stuff.

I know that my next troubleshooting activity is to see if the Create is actually receiving what the IMU is giving it, but I don't really know the best way to do that, and in any case my gut tells me that this is a software or configuration (not hardware) problem.

Does anybody have any suggestions?

Alaina - Singularity University - Mountain View, CA

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answered 2011-06-29 06:34:03 -0500

mmwise

8372 ●45 ●74 ●99 http://www.meloneewise.com/

here are good instructions for adding a sparkfun gyro: http://answers.ros.org/question/717/is-an-imu-required-to-run-turtlebot-stack

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answered 2011-06-29 18:32:02 -0500

Alaina
121 ●4 ●6 ●12 http://9thsense.com/

Thanks to mwise, we figured out that there must have been a loose connection. We attached the same IMU via a different connection to the bay's DB-25 and it's working great now!

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answered 2011-06-29 03:50:48 -0500

Chad Rockey

4541 ●63 ●79 ●98 http://chadrockey.com/

That IMU you showed on sparkfun looks like it only has outputs for I2C. Are you sure you listed the right one? That one doesn't have a RATE pin.

The best way to verify operation is to trace it every step of the way. You said you can see the voltage change. Is this change appropriate for the sensor and your expectation? Does the voltage go up when rotating one way and down when another?

Is there some sort of application that you can use to verify what the BAM reports? Or get some sort of printout?

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answered 2011-06-29 06:03:38 -0500

Alaina
121 ●4 ●6 ●12 http://9thsense.com/

Thanks for the quick response, Chad.

Nuts, I did send the wrong link. That's not the one I have, and I can't find mine on Sparkfun now. Here are pics of the one I'm using (the rear view is a pic of my second IMU, which is still in the bag, but it's exactly the same as the one I'm using):

http://www.flickr.com/photos/32636847@N07/5885257440/in/photostream http://www.flickr.com/photos/32636847@N07/5885257380/in/photostream/

You can see the rate pin there; sorry about sending the wrong link. I have +5V connected to the +5V from the Create, GND connected to ground from the Create, and RATE connected to the analog in on the Create.

Yes, the voltage does exactly what I expect when I rotate the gyro. That part is verified, at least. It's really the only thing I'm confident about. :)

The BAM in this case is just a passthrough; it communicates on the RX/TX pins to replace the serial connection, but passes through the remainder of the pins. I've tried connecting the IMU directly to the correct pins on the Create's DB-25 with the same results: "Still waiting for IMU".

Ideally, I'd like to know that the Create is interpreting the RATE correctly. I'm in a lecture right now, but over lunch I will try two things:

I just noticed that pin 8 (Switched 5V) in the bay is listed in the docs as "provides... analog reference voltage when Create is switched on", so it could be as simple as that, right?
Looks like I can get the AIN voltage (0-5V as 0-1024 digital) as one of the Create's sensor values. I'll do a dump and see what that reports. That should either identify the Create or the software as the problem. I'll get back to you in a couple of hours and let you know.

Thanks again!