Servo troubles.

[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 ?

[Glenn]

Btw, thanks for all help, I'm completly stuck, and I know noone else that uses PBP

[skimask]

@ 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:
        low portb.0
	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
	if b1 > 150 then
               b1 = b1 - 1
        else
               b1 = b1 + 1
        endif
        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
END

This should go left with one button, go right with the other button, and if no buttons are pressed, should 'walk' back to center.
Note the BOLDED statements

[Glenn]

This should go left with one button, go right with the other button, and if no buttons are pressed, should 'walk' back to center.
Note the BOLDED statements

Unfortunatly it gives exactly the same result, the servo goes to the endpoint and stay there..

..And just like in my program, if I uncomment the if-lines it "works" as in it stands in the middle position (more or less)

Strange.

[Acetronics2]

Hi,

Just place

PAUSE 18

just after PULSOUT command ...

instead of Before " GOTO Main" .

Alain

[Glenn]

Hi,

Just place

PAUSE 18

just after PULSOUT command ...

No, exactly the same result

[skimask]

Ok, try this...

@ device HS_OSC,MCLR_OFF,LVP_OFF,WDT_OFF,PROTECT_OFF
DEFINE OSC 4
temp var byte
main:
        for temp = 0 to 255
        pulsout portb.0, temp
	pause 18
        next temp
        for temp = 255 to 0 step -1
        pulsout portb.0, temp
        pause 18
        next temp
        goto main
END

This should do nothing more than swing the servo back and forth, from endpoint to endpoint. It'll probably hang up for a bit at the endpoints and might even move too fast or jerk around a bit trying to catch up to the program.
If it doesn't, you've got something else going on.
It all boils down to breaking it down to it's simplest form and building it back up again.
Try it and report back...

[Glenn]

This should do nothing more than swing the servo back and forth, from endpoint to endpoint. It'll probably hang up for a bit at the endpoints and might even move too fast or jerk around a bit trying to catch up to the program.
If it doesn't, you've got something else going on.
It all boils down to breaking it down to it's simplest form and building it back up again.
Try it and report back...

Well, it swings the servoarm to one endpoint, stops for a while, then all the way to the other endpoint (or near it anyway) and directly start to go back again and repeats everything.

Its not a very smooth movement but it looks ok.

[skimask]

Well, it swings the servoarm to one endpoint, stops for a while, then all the way to the other endpoint (or near it anyway) and directly start to go back again and repeats everything.

Its not a very smooth movement but it looks ok.

Ok, that's good...at least you know stuff is working.

Now take the program and modify it to 'pull the endpoints' in a bit until you get to the actual endpoints.
When it 'stops for awhile', the program is probably trying to drive the servo past it's endpoints. The program goes to 0ms pulse width, but the servo can only actually drive to a 1ms pulse width, actually it'll probably drive farther than that, a lot farther, just not all the way to zero, or by the same token, won't drive all the way to 2.55 ms pulse width.

@ device HS_OSC,MCLR_OFF,LVP_OFF,WDT_OFF,PROTECT_OFF
DEFINE OSC 4
temp var byte
main:
        for temp = 100 to 200
        pulsout portb.0, temp
	pause 17 'try lower numbers until it starts acting even stupider than it's acting now
        next temp
        for temp = 200 to 100 step -1
        pulsout portb.0, temp
        pause 18 'try lower numbers until it starts acting even stupider than it's acting now
        next temp
        goto main
END

Decrease the 100 until it starts pausing at one end (meaning the PIC is trying to over-drive the servo) and increase the 200 until it starts pausing at the other end (again, meaning the PIC is trying to over-drive the servo in the other direction).