Servo control woes

[Dave]

Eriswerks, milestag is right, the servo requires updates every 50 milliseconds or so othwise most servos will shutdown and produce no torque.

Dave Purola,
N8NTA

[Eriswerks]

Thanks for your suggestions. I've whittled down the code to the bare essentials:

@ DEVICE MCLR_OFF,WDT_OFF,PROTECT_OFF

servo var PORTC.5

loop:

pulsout servo,150
pause 18

goto loop


That's the entirety of it, no configuration or anything left out. That ought to center it and hold it there so long as the PIC is powered, but once again it moves all the way to one extreme and stays. I tried other pulsout values from 1 to 2000 just for the fun of it, but I keep getting the same result.

The only thing I can think of is that the internal timer is in its LFINTOSC mode, which is 31kHz and would probably cause any pulse I care to send to look the same to the servo. There must be some language in PicBasic to tell the PIC to which frequency to set the internal oscillator, but I haven't been able to find it.

What am I (still) doing wrong here?

[Acetronics2]

Hi,Eris

Seems you have to read some closer the µChip Datasheet section 3 ...

Lots ( ! ) of registers to set " by hand " that PbP do not handle !!!

to confirm that, just program a dusty 16F84 ... will work properly with your example !!!

Alain

[Bruce]

The internal oscillator doesn't automatically run at 8MHz. You have to
write to OSCCON to switch to 8MHz.

The default value of OSCCON frequency select bits is for 4MHz. See the
datasheet for the default value in this register at power up.

Also PULSOUT toggles the pin twice to produce your pulse, so the initial
state of the pin determins the polarity of the pulse.

You want a high-going pulse for your servo, so clear the pin before the
PULSOUT command.

See if this works.

@ DEVICE INTRC_OSC_NOCLKOUT, MCLR_OFF,WDT_OFF,PROTECT_OFF
DEFINE OSC 8
servo var PORTC.5
i var word

OSCCON = %01110000 ' Now it's going to run at 8MHz

PORTC.5 = 0 ' <-- make pin low before PULSOUT (toggles high then low)
TRISC.5 = 0  ' make pin an output

loop:

for i = 200 to 400
low servo
pulsout servo,i
pause 18
next i

goto loop

[sayzer]

Hi Eriswerks,

Try using another servo or at least make sure that your servo is ok.

Also, as you know, for most of the servos, the pulse range is from 100mS to 200mS.

For some recent ones, range is from 60mS to 240mS (wider movement).

Also, below is a code to consider while playing with servos.

servo var portc.5
freq var byte
pulse var byte


loop:

pot portc.3,255,pulse
pot portc.4,255,freq

if pulse>240 then pulse=240 'Max pulse protection.
If pulse<60 then pulse=60 'Min pulse protection
If freq>30 then freq=30 'Frequency protection
IF freq<5 then freq=5 'Frequency protection

pulsout servo,pulse
pause freq


goto loop
-----------------------
If you also use an LCD, you can see at what value(s) your servo does what it does and how it does.



------------------------------

[Acetronics2]

[QUOTE=sayzer]

Try using another servo or at least make sure that your servo is ok.

Also, as you know, for most of the servos, the pulse range is from 100mS to 200mS.

> That's really new ...


> Mhhhh, I do not know who's inside ... but he has a lot to learn about R/C Equipments ...

Alain

PS: ALL servos accept the 40-50 Hz frame rate ...

[milestag]

---------------------------------------------
There must be some language in PicBasic to tell the PIC to which frequency to set the internal oscillator, but I haven't been able to find it.

What am I (still) doing wrong here?
---------------------------------------------

Yes, there is a PicBasic command... POKE

Use POKE to write values to ANY register in the datasheet. I usually use binary values so it's easier to see and change individual bits:

POKE OSCON, %10110001

(this is a made up value, I don't know what you will need exactly)

[sayzer]

For Acetronics,

This is not the place for your egoistic posts.

Why don’t you go to a primary school and show the little kids how much you know about everything you think you know about?

You can top your ego that way.

[Acetronics2]

Sayzer,

If you want to know, I do not do care about my EGO ... no time for that.

I'd just like you NOT to tell wrong things to those who do not know ...

It's difficult enough to learn pic's programming ... try not to add your own errors nor misunderstandings ... verify first !!!

Alain

Engineer, 30 years of DiY R/C, ... and always doubting ...