Re: Adafruit 16-Channel 12-bit PWM/Servo Driver not driving servos

by walker on Tue Feb 12, 2013 9:01 am

Yes, I WAS being a bit thick about the connection of the LED. I realized that after rereading your post again. I'll run that test again this evening with the correct LED connections.
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Re: Adafruit 16-Channel 12-bit PWM/Servo Driver not driving servos

by walker on Tue Feb 12, 2013 8:06 pm

I've had a chance to test with the LED connected correctly. Just to be clear... Anode (+... the long lead) connected to PWM, and Cathode (-... the short lead) connected to GND. This was on port 0 still running the default Servo sketch. Unfortunately I'm getting nothing out of the LED at all. I tried hitting the reset button several times with the same results. I also tried loading up the pwmtest sketch but no results with that either.

If I move the Anode onto the V+ pin I get full brightness as expected. (I just did this to make sure I hadn't burned out the LED during testing.)

I'm still working on gettig my Rpi configured for i2c. Hopefully I'll have that working tonight.
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Re: Adafruit 16-Channel 12-bit PWM/Servo Driver not driving servos

by walker on Tue Feb 12, 2013 11:20 pm

I got the Rpi set up for gpio and i2c this evening and tested going direct to the PWM board. It seemed like that would be easier than hooking up the logic level converter for the Rpi to Arduino connection.

Unfortunately the i2cdetect command doesn't see the board. I should see a device at 0x40 but just have 2 dashes there. Here is a pic with the connections using a pi cobbler. I wish I had another i2c device hanging around but the only other thing I have is the Arduino.
IMG_0207.-2JPG.jpg
IMG_0207.-2JPG.jpg (488.52 KiB) Viewed 1046 times


I noticed in the pwmtest sketch that you can set the bitrate using TWBR. Can I use it to reduce the bitrate and get a more reliable connection? I can't seem to find docs about TWBR to determine what to set it to.

I guess I'd better get busy wiring the Uno into the i2c bus.
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Re: Adafruit 16-Channel 12-bit PWM/Servo Driver not driving servos

by adafruit_support_bill on Wed Feb 13, 2013 6:59 am

The wiring looks right (although your choice of colors for VCC and GND did confuse me for a bit :wink: ) http://www.ece.rice.edu/~jdw/242_lab4/file.4.html

Slowing down the bit-rate can make it more reliable on longer runs, but with the short jumpers you have there, it should not be an issue. Have you replicated this with your second PWM/Servo breakout too?
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Re: Adafruit 16-Channel 12-bit PWM/Servo Driver not driving servos

by walker on Wed Feb 13, 2013 7:47 am

Yeah! Sorry, I'm pretty new to breadboarding.

Unfortunately I get the same exact behavior from the second board.
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Re: Adafruit 16-Channel 12-bit PWM/Servo Driver not driving servos

by adafruit_support_bill on Wed Feb 13, 2013 9:37 am

I have to admit I am completely out of ideas now. It seems extremely unlikely that you could get two bad boards - especially since we test each one as they come off the production line. But I don't see anything wrong with your assembly or wiring on either the Arduino or the Pi. Thanks for being patient and running all the tests.

If you contact support@adafruit.com with a link to this thread, we can send you replacements.
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Re: Adafruit 16-Channel 12-bit PWM/Servo Driver not driving servos

by walker on Wed Feb 13, 2013 1:17 pm

Thanks, you've been very patient as well. I appreciate the service. I'm willing to send these boards back if you want to test them there. I agree about the chances for both boards being bad. I didn't see anything in the shipping package or the boards themselves that would indicate a problem there. And I don't know of anything in my environment that might cause an issue either.

I'll post back here if the replacement boards work (or not.)
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Re: Adafruit 16-Channel 12-bit PWM/Servo Driver not driving servos

by walker on Tue Feb 19, 2013 9:25 pm

I received the replacement boards this evening and assembled them. Both of them are working as expected! I don't know what was wrong with the two other boards but these two worked great right away. I don't feel I did anything differently but I know it's hard to tell for sure.

I haven't tried it with the Rpi yet, and I haven't tried chaining them but I'm feeling pretty confident after this initial success. Thanks for all of your help!
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Re: Adafruit 16-Channel 12-bit PWM/Servo Driver not driving servos

by adafruit_support_rick on Wed Feb 20, 2013 9:55 am

That's great!
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Re: Adafruit 16-Channel 12-bit PWM/Servo Driver not driving servos

by jonwatts on Fri Mar 22, 2013 6:59 pm

I think I may be in the same boat as Walker.

I have one of these boards hooked up to a rev B Pi (both purchased near the end of January). I've re-checked my soldering and made sure I have continuity from the board through a T-cobbler and back to the Pi. However I can't get i2cdetect -y 1 to show me an address.

  • The green LED on the servo board lights when connected.
  • I didn't think the servo power supply was needed but I've tried it both ways.
  • I even attached an LED to SDA looking for activity. I get a quick flicker when I run i2cdetect.

I'm about to order an i2c LCD backpack to give that a try but ultimately need to get this sorted out.

Thanks for any help!

Jon
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Re: Adafruit 16-Channel 12-bit PWM/Servo Driver not driving servos

by adafruit_support_rick on Fri Mar 22, 2013 9:40 pm

Sounds like it could be an intermittent connection. Maybe try some different breadboard locations. I'd you post a picture of your wiring and of the servo board, we'll have a look.
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