control servo with PCA9685 on node js and sync problems

i'm trying to port a library i wrote for an hexapod robot from Python to Node. The hardware is a Raspberry PI with a PCA9685 driver (https://github.com/101100/pca9685).

I'm facing a problem on when the servo are activated.

There's a loop that estimate the frequencies for every servo and a function that set the frequency for every channel.

The main problem is that the servos dont moves until the loop stops, so i've to use a setTimeout to re-launch the main routine.

the most relevant parts of the code are the walk function, called by a Redis message:

function walk(){
  if(walking){
    step();
  }
  setTimeout(walk,2500);
}

And the stride function, that calculates the frequencies:

function step() {
    (loop for every leg){
        calculate servo frequencies
        pwm.setPulseLength(leg,frequency);
    }
}

All the movements are executed by the servos only after the setTimeout in the walk() function.

I've tried to understand how to use the async library or how to create a callback structure but i probably lack something, and i'm not able to understand where the problem is (maybe in the I2C communication flow).

As a last thing, the setTimeout() method works in some way, but should need to exactly knows when the loop ends, so i can start another loop without overlapping or interruptions from one steps and the next.

Thank you!

via Alessio Bernesco Làvore