Developer

Servo problem with the new red (328) cards?

Hi.

Got my red ATMEGA328 ArduPilot from the latest Sparkfun batch a couple of days ago, and I am having problems getting the servos working.
First I tough the attiny45 was missing failsafe code, so I flashed v15 of the failsafe. No luck there, still no servo response. So I started scoping the in/out pins and I noticed that the servo control input pulses from the receiver are pulled down. Signals out from receiver is ok (3.5v), but the moment I connect them to Ardupilot inputs 1-4 they drop to 1v. CTRL input seems fine and has a 3.5v signal when connected and MUX and MODE status LED are triggered by remote. I have not looked at why the signal is pulled down yet and really don't feel like doing so either, since I bought the Ardupilot so I could start coding right away without designing the electronics first.

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Permalink Reply by Reto on May 2, 2009 at 10:34am
Hi John. If you have 3.5v out from the receiver, I think it might be too low for powering the ArduPilot board. It should receive something like 5v, or at least 4.7-4.8! Check out your battery pack to Rx. even servos run normally at 4.8V, if not at 6v to have faster response and more torque.

3D RoboticsPermalink Reply by Chris Anderson on May 2, 2009 at 10:37am
Looks like you created a short in the soldering. We've got a bunch of the new boards and they all work fine.

Just to confirm, your servos (connected to ArduPilot's OUT pins) aren't working in either RC or autonomous mode? If that's the case, it's almost certainly a soldering error or the connectors are plugged in backwards.

DeveloperPermalink Reply by John Arne Birkeland on May 2, 2009 at 12:46pm
3.5v on the control signal is what you find in most receivers. Some Futaba receivers even go as low as 2.7v. It is power that is 5/6v.

And seeing how it's just a couple of pin headers I can't imagine how they can be soldered wrongly. I just measured to be sure and there are no shorts. As I mentioned, neither servo input or output is working. The only servo port working is CTRL. When I connect a receiver channel to input 1-4 the signal is pulled down to 1v p-p (puls timing is still fine). Output signals are about 0.5v with lots of noise. I can post some scope pictures if you want.
Attachments:

3D RoboticsPermalink Reply by Chris Anderson on May 2, 2009 at 1:15pm
John, I can't quite tell, but it looks like your multiplexer chip was offset by one pin when it was soldered at the factory (ie, it was misplaced). Can you check that? If that's the case, I'm afraid it's a Sparkfun production error and they'll need to replace the board.

DeveloperPermalink Reply by John Arne Birkeland on May 2, 2009 at 1:19pm
Ha! Your right! I can't believe I didn't catch that! Not what you normally look for I guess. :)
But at least something that's quick and easy fix then. Thanks!
Permalink Reply by Reto on May 2, 2009 at 1:30pm
Me wrong about receiver voltage. I didn't read carefully enough you were writing about signal level.
Permalink Reply by Ulf on May 2, 2009 at 1:57pm
Hey John, who's right? :) I got teh same issue, powering 5v to the board (2 pins on the top leftmost corner ), do i have additionally put power on batt pins too?
The servos react in a strange way (shivering).
any ideas?
Permalink Reply by trifasico on May 2, 2009 at 2:17pm
Just in case, i would replace the multiplexer chip. It´s very cheap and probably your's are fault
Permalink Reply by Ulf on May 2, 2009 at 2:42pm
Here's the board, everything looks fine.


AdminPermalink Reply by Thomas J Coyle III on May 2, 2009 at 4:07pm
Ulf,

You should be providing power (+5v) to the board from the receiver through the servo signal input pins in the lower right hand corner of the board.

I believe that Chris has stated that the two power pins in the upper left hand corner require a solder jumper on the board to be functional.

Just a thought.

Regards,
TCIII

3D RoboticsPermalink Reply by Chris Anderson on May 2, 2009 at 6:07pm
Ulf, why are providing power to those two pins in the top left hand corner? As Tom notes, the board is designed to be powered by the servo rail (IN or OUT pins) or via the BATT pins if you switch the solder jumper to BATT (yours is still on SVRO)

DeveloperPermalink Reply by John Arne Birkeland on May 3, 2009 at 3:50am
Regarding Ulf's problem, the top left corner GND and VCC pins are connected directly to the servo rail so I don't see how it would be a problem using them to power the board. The pins that require jumper soldering are clearly marked BATT +/-.

Edit: Ulf. You mentioned powering 5v to the top left pins. Are you also powering the receiver using a battery or ESC? If so that is your problem. You only need to apply power (+5v) to a single part of the chain. Either receiver or ArduPilot.

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