Servo library or AnalogWrite

Using Arduino Motors, Mechanics, Power and CNC
1

Hi everybody,

I'm using an Arduino Due, to run a quadrotor UAV.
So far, i've been using the Servo library to run my 4 GAUI 1050KV DC motor through 4 GUEC GE-010 ESC.
For resolution matters, i want to use the AnalogWrite function instead of the Servo library. However, it seems like the motors are not responding at all. For now i didn't change the PWM resolution so it's still 8 bits.
This code wouldn't make the rotors turn:

int motor4Pin = 8;    

void setup()  { 
pinMode(motor4Pin,OUTPUT);
  analogWrite(motor4Pin, 10); 
  delay(1000);
  analogWrite(motor4Pin, 200); 
} 

void loop()  
{                           
  }

Thanks =)

2

The PWM signal to a servo is a 1 to 2 mS pulse every 20 mS. AnalogWrite() signal is 0 to 100% duty cycle at a much higher rate (varies from port to port) and is not even close to what a servo (your ESC wants). You can use the servo.writeMicroseconds() function to get better resolution than 0 to 180 degrees.

3

You can use the servo.writeMicroseconds() function to get better resolution than 0 to 180 degrees.

Or you can use Servo.write with "angle" values in the range of about 544 to 2500, which is the same as calling the writeMicroseconds function.

4

Thanks for the information.
Is it possible to make AnalogWrite() works in that case by modifying the timers?
Maybe it's a silly question, actually i didn't really get that part; and why i can't use direct PWM now; although i already runned brushless motor like that before.

5

The way servo.write works is that for "angle" values between 0 and 180, it takes a nominal 1856us interval (2400 - 544) and divides it by 180, giving a granularity of about 10us.

If you use servo.writeMicroseconds or "angle" values above 543, you can specify to the microsecond (though there'll be some jitter) the width of your R/C control pulse, so you've got much finer control - about 10x finer.

6

Stoo:
Is it possible to make AnalogWrite() works in that case by modifying the timers?
Maybe it's a silly question, actually i didn't really get that part; and why i can't use direct PWM now; although i already runned brushless motor like that before.

Might that have anything to do with the fact that a servo is different from a brushless motor? It's a bit like saying I used to tell the time with my clock, why can't I do it with my football?

What exactly do you want to do with your servo that you can't do with the Servo library?

...R