[En-Nut-Discussion] Connecting a R/C servo on ethernut

[Lars Andersson]

A R/C servo works like this. Everytime there is a positive pulse on
the signal line the servo measures the length of the pulse.
if the pulse is 1.5 ms the servo moves towards it's mid position if
it is not already there.
It will move if needed for every pulse that arrives. If no pulses
arrive, the servo will not move, but it will be "soft" and not
able to resist external force.

1 ms is one end, 1.5 ms is mid position and 2 ms is the other 
end of travel.

Ground has to be common with ethernut as a reference for the 
pulse signal.
Power is not very critical, 4.5 to 6 V is OK, the servo can 
draw a lot of current when moving, especially big ones, 1 A 
power supply capacity is OK for one small servo.

So you want to generate positive TTL pulses that are of varible 
length 1 to 2 ms 10 to 20 times per second or so. The pulse 
length is critical, the time between pulses is not critical.    

Regards,
Lars H. Andersson


-----Original Message-----
From: en-nut-discussion-bounces at egnite.de
[mailto:en-nut-discussion-bounces at egnite.de] On Behalf Of Sigurd Kleppan
Sent: Friday, 16 January, 2004 14:50
To: en-nut-discussion at egnite.de
Subject: [En-Nut-Discussion] Connecting a R/C servo on ethernut


I have looked at some articles about using a r/c servo on ethernut. 
Is it correct to use this code? Will a servo work?

void servo(){
 while(2>1){
  NutDelay(20);
  outp(0xFF,PORTD);
  NutDelay(1);
  outp(0x00,PORTD);
 }
}

I have tried this code, but it won't work? Do someone have a better
example??

Is it possible to use external adaptor to power the servo and only give
the signal from ethernut board, or do i have to use same ground on
signal and power?

Can ethernut 5V= supply a r/c servo?

Sigurd

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