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@0:9e0f295a55a4, 2012-12-14 (annotated)

Committer:
geotec
Date:
Fri Dec 14 14:34:22 2012 +0000
Revision:
0:9e0f295a55a4
Initial commit

Who changed what in which revision?

UserRevisionLine numberNew contents of line
geotec 0:9e0f295a55a4 1 #include "mbed.h"
geotec 0:9e0f295a55a4 2 #include "PwmOscillator.h"
geotec 0:9e0f295a55a4 3 #include "FastPWM.h"
geotec 0:9e0f295a55a4 4
geotec 0:9e0f295a55a4 5 FastPWM pinOut(p22);
geotec 0:9e0f295a55a4 6
geotec 0:9e0f295a55a4 7 double _period_us = 0;
geotec 0:9e0f295a55a4 8 double _pulsewidth_us = 0;
geotec 0:9e0f295a55a4 9
geotec 0:9e0f295a55a4 10
geotec 0:9e0f295a55a4 11 void PwmOscillator::initWithFrequency(int frequencyHz)
geotec 0:9e0f295a55a4 12 {
geotec 0:9e0f295a55a4 13 _period_us = (1.0 / (double)frequencyHz)*1000000;
geotec 0:9e0f295a55a4 14 _pulsewidth_us = _period_us / 2.0;
geotec 0:9e0f295a55a4 15 pinOut.period_us(_period_us);
geotec 0:9e0f295a55a4 16 }
geotec 0:9e0f295a55a4 17
geotec 0:9e0f295a55a4 18 void PwmOscillator::start()
geotec 0:9e0f295a55a4 19 {
geotec 0:9e0f295a55a4 20 pinOut.pulsewidth_us(_pulsewidth_us);
geotec 0:9e0f295a55a4 21 }
geotec 0:9e0f295a55a4 22
geotec 0:9e0f295a55a4 23 void PwmOscillator::stop()
geotec 0:9e0f295a55a4 24 {
geotec 0:9e0f295a55a4 25 pinOut = 0;
geotec 0:9e0f295a55a4 26 }