bunt _ / PwmOscillator

Creates square-wave frequency output on pin p22. Custom frequency between 1Hz and 48 MHz. (LPC 1768)

Dependencies:   FastPWM

Creates square-wave frequency output on pin22 with custom frequency.

Tested for frequencies from 1Hz to 48MHz. The accuracy depends heavily on the frequency - at 12, 24, 48 MHz the frequency deviation is less than 1%, but at 20 MHz it is about 20%.

Uses Library FastPWM ( http://mbed.org/users/Sissors/code/FastPWM/ ). For LPC 1768.

How to use this Library:

#include "mbed.h"
#include "PwmOscillator.h"

PwmOscillator oscillator;
DigitalOut led1(LED1);

int main() 
{
    oscillator.initWithFrequency(8000000);     // initialize oscillator instance (pin p22) with custom frequency, here: 8MHz
    led1=1;                                    // optional: indicator LED shows that oscillator is running
    oscillator.start();                        // start oscillator
    wait(5);                                   // optional: oscillator is running 5 seconds
    oscillator.stop();                         // stop oscillator
    led1=0;
}

PwmOscillator.cpp

Committer:
geotec
Date:
2012-12-14
Revision:
2:d9fea7c1fc8d
Parent:
0:9e0f295a55a4

File content as of revision 2:d9fea7c1fc8d:

#include "mbed.h"
#include "PwmOscillator.h"
#include "FastPWM.h"

FastPWM pinOut(p22);

double _period_us = 0;
double _pulsewidth_us = 0;


void PwmOscillator::initWithFrequency(int frequencyHz)
{
    _period_us = (1.0 / (double)frequencyHz)*1000000;
    _pulsewidth_us = _period_us / 2.0;
    pinOut.period_us(_period_us);  
}

void PwmOscillator::start()
{    
    pinOut.pulsewidth_us(_pulsewidth_us);
}

void PwmOscillator::stop()
{
    pinOut = 0;
}