Analog

Analog output is essentially PWM signal. It has a duty and freq. Duty can take any values including and betweeen 0 and 1. Frequency is in Hertz and BeagleBone supports any frequency upto 1 MHz.

There are also dedicated pins on BeagleBone which is attached to ADC and can work as analog input pins. Those pins are 'P9_33' to 'P9_40'.

analogWrite(pin, value, freq, callback[err|null])

• pin is the identifier of a pin on the P9 or P8 header ex: P8_13. Only SOME pins can work as PWM pins. Please refer BeagleBone pin diagram to identify those pins
• value is any floating point value including and between 0 and 1. It is essentially duty cycle of PWM signal.
• freq is the frequency of PWM signal. If you dont provide this value, it defaults to 2000 Hz.
• callback function first argument is 'verror' object in case of error or null otherwise.

Example

var b = require('octalbonescript'); //load the library

var pin = 'P8_13'; //the pin to operate on

// below code will assign analog output mode to pin and when the pin is ready, it will write 0.5 value.
b.pinMode(pin, b.ANALOG_OUTPUT, function(err1) {
  if (err1) {
    console.error(err1.message); //output any error
    return;
  }
  b.analogWrite(pin, 0.5, 2000, function(err2) {
      if (err2) {
        console.error(err2.message); //output any error
        return;
      }
  });
});

analogRead(pin, callback[err|null, value])

• pin is the pin identifier. Only P9_33 to P9_40 can work as analog input pins
• callback first argument is 'verror' object in case of error, null otherwise. Second argument is the value of analog input given as floting point number including and between 0 and 1. 0V corresponds to 0 and 1.8V corresponds to 1.

Example

// no pinmode is required for analogRead as those pins are dedicated.
var b = require('octalbonescript'); //load the library

var pin = 'P9_33'; //the pin to operate on
b.analogRead(pin, function(err, value){
  if(err){
    console.error(err.message);
    return;
  }
  console.log(value); // value is floating point number between 0 and 1.
});

startAnalog(pin, callback[err|null])

• pin is any PWM pin identifier in P8 or P9
• callback will have first argument as 'verror' object if there is error starting PWM. Null otherwise

This function is automatically called when you perform analogWrite but this is provided in case you manually stop analog output.

Example

var b = require('octalbonescript'); //load the library

var pin = 'P9_13'; //the pin to operate on
b.startAnalog(pin, function(err){
  if(err){
    console.error(err.message);
  }
});

stopAnalog(pin, callback[err|null])

• pin is any PWM pin identifier in P8 or P9
• callback will have first argument as 'verror' object if there is error starting PWM. Null otherwise

This function stops analog output on given pin. You can call startAnalog to start it again.

Example

var b = require('octalbonescript'); //load the library

var pin = 'P9_13'; //the pin to operate on
b.stopAnalog(pin, function(err){
  if(err){
    console.error(err.message);
  }
});