Help with Servo32v7 - Stop/Pause Servo

ckbw33 · 2012-05-18 08:12

I hope this is a quick/easy question!

I'm using Servo32v7, and I'd like to let the servo "relax". I don't care about it's subsequent position, I'd just like to cut the power to the servo after I've finished actuating it.

I could not find a "stop" function in the object, but this seems like a straighforward task (i.e. stop pulses on that pin). The assembly portion is a little hairy for my Propeller knowlege depth, so can anyone suggest code for a "stop" PUB?

Mike Green · 2012-05-18 08:21

You turn off a servo by using an invalid servo pulse width. The valid range is 500 (0.5ms) to 2500 (2.5ms), so anything less than 500 or greater than 2500 will work. The I/O pin will be set to input mode. The servo will shut itself off after 20-30ms typically. There are comments in the SetRamp and Set routines that discuss this.

ckbw33 · 2012-05-18 08:26

Fantastic! I will give that a shot. Thanks for the quick response. I could gather the pin was switched to an input when it was out of range, but I'm still mystified by the globalness of variables when ASM and SPIN are in the same object. Thanks!!!

Duane Degn · 2012-05-18 08:42

The Start method doesn't return anything.

It seems like it would be a good idea if it at least returned the cog number so the parent object could stop the cog if needed.

I suppose anyone wanting to top and retart a cog would probably know how to do this themseleves, but it just seems odd there isn't any information returned from the Start method.

Changing:

PUB Start
    RampFlag := 0 
    ZoneClocks := (clkfreq / _1uS * ZonePeriod)                                 'calculate # of clocks per ZonePeriod
    NoGlitch   := $FFFF_FFFF-(clkfreq / _1uS * NoGlitchWindow)                  'calculate # of clocks for GlitchFree servos. Problem occurs when 'cnt' value rollover is less than the servo's pulse width.                                                                                                                                                                                                                         
    cognew(@ServoStart,@ZoneClocks)

To:

PUB Start
    RampFlag := 0 
    ZoneClocks := (clkfreq / _1uS * ZonePeriod)                                 'calculate # of clocks per ZonePeriod
    NoGlitch   := $FFFF_FFFF-(clkfreq / _1uS * NoGlitchWindow)                  'calculate # of clocks for GlitchFree servos. Problem occurs when 'cnt' value rollover is less than the servo's pulse width.                                                                                                                                                                                                                         
   [B]result := [/B]cognew(@ServoStart,@ZoneClocks)

The added "result :=" doesn't even increase the program size (which I think is kind of strange).

Help with Servo32v7 - Stop/Pause Servo

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