bunt _
Counts pulses on pin p29. Pulse frequency can be up to 48 MHz.
Example, counting 48MHz-pulses on pin p29 generated by pin p22 with PwmOscillator (https://mbed.org/users/geotec/code/PwmOscillator/). Pins p22 & p29 must be connected. Count is triggered when pin p30 = high (I connected oscillator with 9kHz that triggered periodically).
#include "mbed.h"
#include "PwmOscillator.h"
#include "PulseCounter.h"
Serial usbPC(USBTX, USBRX); // sends log messages via USB to PC terminal
PwmOscillator pulseGenerator; // generates pulses to be count (48 MHz) on pin p22. Connect this pin to p29 (counter input).
PulseCounter pulseCounter; // counts the pulses on pin p29 between trigger events (= rising edges) on pin p30.
int main()
{
usbPC.printf("---> start <---\n");
pulseGenerator.initWithFrequency(48000000);
pulseCounter.init();
pulseGenerator.start();
pulseCounter.start();
wait(1); // waiting 1 second for trigger events (pin30: rising edge). Count pulses between trigger events.
pulseCounter.stop();
pulseGenerator.stop();
// read & print pulseCounter results
uint32_t pulseCounterResults[20];
pulseCounter.counterArray(&pulseCounterResults[0],sizeof pulseCounterResults / sizeof (uint32_t));
for(int i = 0; i < (sizeof pulseCounterResults / sizeof (uint32_t)); i++) {
usbPC.printf("counter of trigger event %i = %u\n",i,pulseCounterResults[i]);
}
//
usbPC.printf(" finished.\n");
}
Diff: PulseCounter.cpp
- Revision:
- 0:157c2fddaa68
- Child:
- 1:83149916f8a9
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/PulseCounter.cpp Sat Dec 15 14:26:47 2012 +0000
@@ -0,0 +1,123 @@
+#include "mbed.h"
+#include "PulseCounter.h"
+
+PulseCounter *PulseCounter::instance;
+
+extern int CLOCK_FREQUENCY;
+
+void PulseCounter::init()
+{
+ instance = this; // pointer to instance
+
+ // Power Control for Peripherals Register
+ LPC_SC->PCONP |= (1<<22); // Bit 22: 1 = Timer2 power on
+
+ // Pin Function Select Register
+ LPC_PINCON->PINSEL0 |= (0x3<<8); // Bits 9/8: 1/1 = pin function CAP2.0 (p30)
+ LPC_PINCON->PINSEL0 |= (0x3<<10); // Bits 11/10: 1/1 = pin function CAP2.1 (p29)
+
+ // Peripheral Clock Selection Register
+ LPC_SC->PCLKSEL1 |= (0x1<<12); // Bits 13/12: 0/1 = CCLK ( 96 MHz )
+ // Prescale Register
+ LPC_TIM2->PR = 0x0; // 0 = no prescaling
+
+ // Count Control Register
+ LPC_TIM2->CTCR = 0x7; // Bits 1/0: 1/1 = timer is incremented on rising & falling edges on clock sample capture pin
+ // Bits 3/2: 0/1 = clock sample capture pin: CAP2.1 (p29), (p29 signal is counter clock)
+
+ // Capture Control Register
+ LPC_TIM2->CCR = 0x5; // Bits 2/1/0: 1/0/1 = capture on rising edge / generate interrupt on event
+ // Bits 5/4/3: 0/0/0 = don't capture - this is the clock sample capture pin
+
+ // Set custom method to be called on Timer2 interrupt
+ NVIC_DisableIRQ(TIMER2_IRQn);
+ NVIC_SetVector(TIMER2_IRQn, (uint32_t)&_triggerInterrupt);
+ NVIC_EnableIRQ(TIMER2_IRQn);
+ //
+
+ LPC_TIM2->TCR = 0x2; // Timer2 count reset
+ LPC_TIM2->TCR = 0x0; // Timer2 disabled
+
+ _hasFinishedCounting = true;
+}
+
+void PulseCounter::start()
+{
+ // reset array pointer to first array element
+ int arrayLength = sizeof(_pulseCountArray)/sizeof(uint32_t);
+ for(int i = 0; i < arrayLength; i++) {
+ _pulseCountArray[i] = 0;
+ }
+ _arrayPointer = &_pulseCountArray[0];
+ _triggerCounter = 0;
+ //
+
+ LPC_TIM2->TCR = 1; // Timer2 start
+ NVIC_EnableIRQ(TIMER2_IRQn); // enable capture interrupt
+
+ _hasFinishedCounting = false;
+}
+
+void PulseCounter::stop()
+{
+ LPC_TIM2->TCR = 0; // Timer2 stop
+ NVIC_DisableIRQ(TIMER2_IRQn); // disable capture interrupt
+
+ _hasFinishedCounting = true;
+}
+
+void PulseCounter::counterArray(int* counterArray, int counterArrayLength)
+{
+ int i = 1;
+ if(_hasFinishedCounting == true) {
+ while(i <= _pulseCountArrayLength) {
+ *counterArray = _pulseCountArray[i];
+ counterArray++;
+ i++;
+ if (i > counterArrayLength) {
+ // parameter counterArray has less elements than pulseCountArray. Stop copying elements.
+ break;
+ }
+ }
+ } else {
+ // User didn't call stop() before reading pulseCountArray - prevent simultaneous read and write on array. Just return zero array.
+ while(i <= _pulseCountArrayLength) {
+ *counterArray = 0;
+ counterArray++;
+ i++;
+ if (i > counterArrayLength) {
+ // parameter counterArray has less elements than pulseCountArray. Stop copying elements.
+ break;
+ }
+ }
+ }
+
+ // if parameter counterArray has more elements than pulseCountArray. Fill up with zeros.
+ if(counterArrayLength > _pulseCountArrayLength) {
+ while(i <= counterArrayLength) {
+ *counterArray = 0;
+ counterArray++;
+ i++;
+ }
+ }
+}
+
+void PulseCounter::_triggerInterrupt()
+{
+ instance->_arrayPointer++; // increment array pointer
+ wait_us(1); // incrementing pointer needs a little time
+ *instance->_arrayPointer = LPC_TIM2->CR0; // store capture time in eventTimeCount-Array
+
+ LPC_TIM2->TCR = 0x2; // Timer2 count reset
+ LPC_TIM2->TCR = 0x0; // Timer2 disabled
+ LPC_TIM2->TCR = 0x1; // Timer2 enabled
+
+ instance->_triggerCounter++;
+ if (instance->_triggerCounter > _pulseCountArrayLength) {
+ instance->_arrayPointer = &instance->_pulseCountArray[0];
+ instance->_triggerCounter = 0;
+ }
+
+ LPC_TIM2->IR = 0x10; // clear interrupt
+}
+