bunt _
Creates square-wave frequency output on pin p22. Custom frequency between 1Hz and 48 MHz. (LPC 1768)
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;
}
Revision 0:9e0f295a55a4, committed 2012-12-14
- Comitter:
- geotec
- Date:
- Fri Dec 14 14:34:22 2012 +0000
- Child:
- 1:4bbb380a1089
- Commit message:
- Initial commit
Changed in this revision
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/FastPWM.lib Fri Dec 14 14:34:22 2012 +0000 @@ -0,0 +1,1 @@ +http://mbed.org/users/Sissors/code/FastPWM/#3094d3806cfc
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/PwmOscillator.cpp Fri Dec 14 14:34:22 2012 +0000
@@ -0,0 +1,26 @@
+#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;
+}
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/PwmOscillator.h Fri Dec 14 14:34:22 2012 +0000
@@ -0,0 +1,22 @@
+#include "mbed.h"
+
+/** Creates square-wave frequency output on pin22 with custom frequency. Tested for frequency range from 1Hz to 48MHz.
+ * The accuracy is depends 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/ ). */
+class PwmOscillator
+{
+
+public:
+
+ /** Initialize PwmOscillator instance with frequency [Hz].
+ * @param frequencyHz = frequency in Hz (1 ... 48000000) */
+ void initWithFrequency(int frequencyHz);
+
+ /** Start oscillator
+ */
+ void start();
+
+ /** Stop oscillator
+ */
+ void stop();
+};