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"); }
PulseCounter.h
- Committer:
- geotec
- Date:
- 2012-12-15
- Revision:
- 0:157c2fddaa68
- Child:
- 1:83149916f8a9
File content as of revision 0:157c2fddaa68:
#ifndef MBED_PULSECOUNTER_H #define MBED_PULSECOUNTER_H #include "mbed.h" const int _pulseCountArrayLength = 20; /** Counts pulses on pin29 coming in with a frequency up to 48 MHz. The counter is read (and reset to 0) by rising edge (trigger event) on pin30. * These events can be triggered at a rate up to 9kHz. The counter results are stored in a "circular array" of 20 elements. * ("circular array" = array pointer increments each time a new value is stored into the array; if pointer reaches last element, it is redirected to first element) * */ class PulseCounter { public: /** Initializer for PulseCounter instance */ void init(); /** Start counter */ void start(); /** Stop counter */ void stop(); /** Read pulse count results into external array. Do not call this method before you called method stop() - otherwise it will return zeros. * @param counterArray = Pointer to array in which the pulse count results should be read into. * @param counterArrayLength = Size of counterArray. Should be 20 or less. If more than 20, remaining elements will be filled with zeros. * @code #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 int pulseCounterResults[20]; pulseCounter.counterArray(&pulseCounterResults[0],sizeof pulseCounterResults / sizeof (int)); for(int i = 0; i < (sizeof pulseCounterResults / sizeof (int)); i++) { usbPC.printf("counter of trigger event %i = %i\n",i,pulseCounterResults[i]); } // usbPC.printf(" finished.\n"); } * @endcode */ void counterArray(int* counterArray, int counterArrayLength); private: static void _triggerInterrupt(); static PulseCounter *instance; bool _hasFinishedCounting; volatile int _triggerCounter; volatile uint32_t *_arrayPointer; volatile uint32_t _pulseCountArray[_pulseCountArrayLength + 1]; }; #endif