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Re: [Paparazzi-devel] Preventing Servos from Cycling at Boot

From: Luke Ionno
Subject: Re: [Paparazzi-devel] Preventing Servos from Cycling at Boot
Date: Mon, 23 May 2011 10:15:43 -0400

I looked into using a MOSFET on a GPIO to disable the PWM feed until the autopilot was fully booted; I hit a snag when I found the state of the GIPO wasn’t all that well-defined during boot.  An RC switch probably would have worked though; should have thought of that. 
At this point, I think I’ll go and try coding a new hard-coded case.  Not a great long-term solution, but it will address the immediate problem.
Sent: Friday, May 20, 2011 6:58 PM
Subject: Re: [Paparazzi-devel] Preventing Servos from Cycling at Boot

Is there a possibility simply to put a small R/C or similar switch between the servo and the TWOG that can be turned on after initialization and before flight? Of course, more weight and complexity.

Just a thought.

-Stephen Dwyer

On Fri, May 20, 2011 at 4:36 PM, antoine drouin <address@hidden> wrote:
Hi Luke

On the twog, I believe sw/airborne/arch/lpc21/servos_4017_hw.c is used.
On initialization, it starts by settings all servo to 1.5ms
It has a couple hard coded special cases when  SERVO_MOTOR,
outputs the specific SERVO_MOTOR_NEUTRAL etc... values.

On stm32 which uses
, the behaviour is different and I believe servos are not commanded
(no PWM is output)  until the autopilot runs and makes the first call
to  actuators_commit

I'm not sure what the right thing to do is, as actuators are fed with
commands produced by the autopilot. There is nevertheless a failsafe
value defined for those commands ( it is used on failure of the
autopilot process - which only make sense on systems that have a level
of protection between the autopilot and fbw processes). Maybe a thing
to do would be to command servos using values computed from the
failsafe commands, but that would mean those values would have to be
computed before the actuators hardware initialization.



On Sat, May 21, 2011 at 12:11 AM, Luke Ionno <address@hidden> wrote:
> Question for everybody...
> I’ve got a TWOG-based airframe with a servo-operated release mechanism; it’s
> a little tricky to reset, and unfortunately, at boot, all the servos cycle,
> causing the release to trigger.  Is there any way to prevent the initial
> servo cycling?
> Thanks!
> ~Luke
> _______________________________________________
> Paparazzi-devel mailing list
> address@hidden

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