Servo troubles.

[skimask]

Aha.. Hmm, but my original code didnt have those pauses, and still doesnt work..
But I'll change my testcode and remove the pauses and makes it update continuosly.
..Also, if I make a loop that just send 150 to the servo, it stands in one of the nedpositions.. shouldnt that (150) be the middle position ?

If your original code was going too FAST, you might see the same results.
And a middle position of 150 (1.5ms) is almost an arbitrary number...might be 160, might be 140-ish. Depends on the servo and what day of the week it was made...

@ device INTRC_OSC_NOCLKOUT,MCLR_OFF,LVP_OFF,WDT_OFF,PROTECT_OFF
DEFINE OSC 4
ct var byte : ct2 var byte : ct = 150 : low portb.1
main:
     for ct = 150 to 250 step 1    'sweep one way
          for ct2 = 1 to 50
               pulsout portb.0, ct
               pause 18
          next ct2
     next ct
     for ct2 = 1 to 50    'hang out there for a bit
          pulsout portb.0, ct
          pause 18
     next ct2
     for ct = 250 to 150 step -1     'sweep the other way
           for ct2 = 1 to 50
                pulsout portb.0, ct
                pause 18
           next ct2
     next ct
     for ct2 = 1 to 50     'hang out there for a bit
          pulsout portb.0, ct
          pause 18
     next ct2
goto main

[Glenn]

Hmm, well that works, sort of.. its not centering and its not full to the ends..

I tried my old "center the servo" code with slightly modifications too:

' servocenter
@ device INTRC_OSC_NOCLKOUT,MCLR_OFF,LVP_OFF,WDT_OFF,PROTECT_OFF
DEFINE OSC 4

start:
	pulsout portb.0, 150
	pause 18
	goto start

..Well, this is strange..

The first time I tried it it seemed to work.. but if i moved the servoarm (with power disconnected ofcourse) it gives very strange results.

If its in 180 degrees position, or close to that, it will work, it will center (more or less) the arm and hold it there.. HOWEVER.. if its in another position, it will just hold the current position ??

this is so strange.

[Glenn]

Ok, now I suspected the servo, so I changed the brand new chinese servo to an old one from my box of "old RC stuff", and with two different (working) hitec servos (different models) I get another result, they go to one endpoint and stay there, regardless of the original position ??

[skimask]

Ok, now I suspected the servo, so I changed the brand new chinese servo to an old one from my box of "old RC stuff", and with two different (working) hitec servos (different models) I get another result, they go to one endpoint and stay there, regardless of the original position ??

That's why when you buy a transmitter, it has trim settings on it. when you change servo's in an airplane, generally you have to re-center it, reset the endpoints, etc.etc.etc.
If the one servo isn't going end to end, increase the end points in the program.
And I was wrong. The endpoints in that previous program should've been 100 and 200, not 150 and 250.

[Acetronics2]

Hi, Glenn

Just try

LOW PortB.0

just before the PULSOUT Command ...

Alain

[skimask]

Just try
LOW PortB.0
just before the PULSOUT Command ...

Arg! In post #4, that should've been a PortB.0 instead of the posted PortB.1 in the third line!!!

[Macgman2000]

try just a simple code to make sure your servo is functioning correctly. I found a servo that seemed to drift. I thought it was my code. So i wrote a simple code that sets my pulse widths to left, center and right limits.
Yes I do violate the 20ms refresh rate but if all you care about is moving to positions to verify servo operation this is quick and dirty.

start:
portd.0=1
pausus 1000
portd.0=0

pause 2000

portd.0=1
pausus 1500
portd.0=0

pause 2000

portd.0=1
pausus 2000
portd.0=0

pause 2000

goto start


Nick

[Glenn]

Strangly enough, it kinda work now.. a bit out of scale and so on, but mostly work, after the 'low bortb.0'

HOWEVER..

Now I got to the next part, trying to actually being able to move the servo myself.. so I wrote a bit of code that I thought should work.

@ device HS_OSC,MCLR_OFF,LVP_OFF,WDT_OFF,PROTECT_OFF
DEFINE OSC 4

'Use b1 to hold pulse width variable for servo 1

b1 var byte

'initialize variables

b1 = 150

low portb.0		' put the servoport low.

main:

	pulsout portb.0, b1		'send current servo 1 position out
	
	if porta.0 = 0 then left1	'check for pressed switch 0
	if porta.1 = 0 then right1	'check for pressed switch 1

	pause 18
	
	goto main
	
left1:
	b1 = b1 + 1
	if b1 >254 then max1
	goto main

right1:
	b1 = b1 - 1
	if b1 <75 then min1
	goto main

max1:
	b1 = 75
	goto main
	
min1:
	b1 = 254
	goto main

..I have pullup-resistors (10k) on a0 and a1 and wiring them to ground when I activates them.

..Well, the problem is that the servo just goes to one endposition and stay there regardless what I do with a0 and a1 ?

..HOWEVER.. if I comment out theese two lines:

        if porta.0 = 0 then left1	'check for pressed switch 0
	if porta.1 = 0 then right1	'check for pressed switch 1

..The servo "works", it put itself in the middle position (well not really middle but more or less.)

Why ? ..I could think that my subroutines are destroying the timing, bit it aint working even if I dont touch the inputs ?