RoboticsConnection Forum

Forum Home

Discussions

Serializer Robot Controller

Serializer enco...

Serializer encoder problem

10/26/2007 11:24:10 AM

rpg

35 posts

Serializer encoder problem

Hello,

I'm having trouble with the readings from the Serializer's onboard quadrature encoder ports. I have a recent board (purchased within the last month) and the latest firmware (1.4.2). I am using the onboard H-bridges to drive two Banebots 7.2 volt DC motors. I am also using the Robotics Connection quadrature encoder kit with 44-count spoke patterns.

The encoders appear to be working fine--both encoders blink both LED's as the wheels rotate and both encoders appear to blink at the same rate for the same wheel speed. However, the encoder counts as returned by the getenc 1 2 command are wildly different depending on whether I connect an encoder to port 1 or 2 on the Serializer. For example, when running a wheel at a speed of 100 (e.g pwm 1:100) for 15 seconds, I get a count of 697 on encoder port 1. But if I connect the same encoder to encoder port 2 and repeat the test, I get a count of 4858. This is a very consistent pattern. I can switch cables or encoders, and the count on encoder port 1 is always much lower than on port 2. I've a tried the experiment with both cfg enc 0 and cfg enc 1 and get the same result. I have also done a restore command and get the same result. And it doesn't seem to depend on the vpid parameters either.

Does this mean I have a bad encoder port on the Serializer, or is there something else I can try?

Thanks!
patrick

10/26/2007 12:20:26 PM

ringo

36 posts

Re: Serializer encoder problem

I'll run a test this weekend to make sure we did not break something in the 1.4.2 Fw. If it appears to work ok then there must be something wrong with either the encoder or the serializer. If it was a bad encoder port on the serializer I would think you would get 0 counts, not just a lower number. I'll let you know what I find as soon as I run the tests and we will get you working.

Ringo

Ringo Davis, Hardware Technical Lead RoboticsConnection.com

10/26/2007 12:52:42 PM

rpg

35 posts

Re: Serializer encoder problem

Thanks Ringo. BTW, I had the same problem with Fw 1.4.1 or 1.4.0 (sorry I can't remember) that came with the Serializier. I upgraded to 1.4.2 just this morning to see if it would fix the problem but it did not.

--patrick

10/26/2007 2:03:11 PM

ringo

36 posts

Re: Serializer encoder problem

ok, well that probably tells me it is not the Fw then, I would assume somebody else would have mentioned it by now if it was. This is a weird problem. have you tried using the MOGO command yet? Probably not since you can't get consistent readings but just a thought.

Try this. Just rotate the wheel by hand 1 revolution and see what it returns. I would assume this would be as inconsistent as running with PWM, but who knows, maybe it will be a clue.

Ringo

Ringo Davis, Hardware Technical Lead RoboticsConnection.com

10/26/2007 2:18:54 PM

rpg

35 posts

Re: Serializer encoder problem

OK, I'll try that when I get home tonight and post the results. An no, I haven't experimented with the mogo command yet.

--patrick

Page 1 of 5

...5

Discussions

Serializer Robot Controller

Serializer enco...