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Topic: Frequency Counter Library (Read 44 times) previous topic - next topic



for the newbies, can you give a short description &  current state ?
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

doug metzler

Feb 29, 2012, 12:06 am Last Edit: Feb 29, 2012, 05:22 am by doug metzler Reason: 1
I modified the cpp file to work with the mega2560.  It was pretty easy.  Uses pin 47 same as the 1280.  It works but sadly it does not play nice with the servo module (presumably they both use the same timer).

Code: [Select]

 FreqCounter.h -
 Using Counter1 for counting Frequency on T1 / PD5 / digitalPin 5
 Uses Counter5 on the Mega digitalPin 47

 Using Timer2 for Gatetime generation

 Martin Nawrath KHM LAB3
 Kunsthochschule für Medien Köln
 Academy of Media Arts

   Dec/08 - V0.0
   May/20  modified by mem to support Mega usting T5 /PL2 on digitalPin 47

 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
 License as published by the Free Software Foundation; either
 version 2.1 of the License, or (at your option) any later version.

 This library is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 Lesser General Public License for more details.

 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

#include <FreqCounter.h>

unsigned long FreqCounter::f_freq;

volatile unsigned char FreqCounter::f_ready;
volatile unsigned char FreqCounter::f_mlt;
volatile unsigned int FreqCounter::f_tics;
volatile unsigned int FreqCounter::f_period;
volatile unsigned int FreqCounter::f_comp;

// 16 bit timer defines added by mem to enable redifining the timer used
#if defined(__AVR_ATmega2560__)
#define TCCRnA TCCR5A
#define TCCRnB TCCR5B
#define TCNTn  TCNT5
#define TIFRn  TIFR5
#define TOVn   TOV5
#elif defined(__AVR_ATmega1280__)
#define TCCRnA TCCR5A
#define TCCRnB TCCR5B
#define TCNTn  TCNT5
#define TIFRn  TIFR5
#define TOVn   TOV5
#elif defined (__AVR_ATmega168__)
#define TCCRnA TCCR1A
#define TCCRnB TCCR1B
#define TCNTn  TCNT1
#define TIFRn  TIFR1
#define TOVn   TOV1
#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))

void FreqCounter::start(int ms) {

 if (f_comp ==0) f_comp=1;

// hardware counter setup ( refer atmega168.pdf chapter 16-bit counter1)
 TCCRnA=0;     // reset timer/countern control register A
 TCCRnB=0;  // reset timer/countern control register A
 TCNTn=0;     // counter value = 0
 // set timer/counter1 hardware as counter , counts events on pin Tn ( arduino pin 5 on 168,47 on Mega )
 // normal mode, wgm10 .. wgm13 = 0
 sbi (TCCRnB ,CS10); // External clock source on Tn pin. Clock on rising edge.
 sbi (TCCRnB ,CS11);
 sbi (TCCRnB ,CS12);

 // timer2 setup / is used for frequency measurement gatetime generation
 // timer 2 presaler set to 256 / timer 2 clock = 16Mhz / 256 = 62500 Hz
 cbi (TCCR2B ,CS20);
 sbi (TCCR2B ,CS21);
 sbi (TCCR2B ,CS22);

 //set timer2 to CTC Mode
 cbi (TCCR2A ,WGM20);
 sbi (TCCR2A ,WGM21);
 cbi (TCCR2B ,WGM22);
 OCR2A = 124;

 f_ready=0;    // reset period measure flag
 f_tics=0;     // reset interrupt counter
 sbi (GTCCR,PSRASY); // reset presacler counting
 TCNT2=0; // timer2=0
 TCNTn=0; // Countern = 0

 cbi (TIMSK0,TOIE0); // disable Timer0  //disable  millis and delay
 sbi (TIMSK2,OCIE2A); // enable Timer2 Interrupt

 TCCRnB = TCCRnB | 7; //  Counter Clock source = pin Tn , start counting now


//  Timer2 Interrupt Service is invoked by hardware Timer2 every 2ms = 500 Hz
//  16Mhz / 256 / 125 = 500 Hz
//  here the gatetime generation for freq. measurement takes place:

// multiple 2ms = gate time = 100 ms
if (FreqCounter::f_tics >= FreqCounter::f_period) {
   // end of gate time, measurement ready

  // GateCalibration Value, set to zero error with reference frequency counter
   delayMicroseconds(FreqCounter::f_comp); // 0.01=1/ 0.1=12 / 1=120 sec
   TCCRnB = TCCRnB & ~7;   // Gate Off  / Counter Tn stopped
   cbi (TIMSK2,OCIE2A);    // disable Timer2 Interrupt
   sbi (TIMSK0,TOIE0);     // enable Timer0 again // millis and delay
   FreqCounter::f_ready=1; // set global flag for end count period

   // calculate now frequeny value
   FreqCounter::f_freq=0x10000 * FreqCounter::f_mlt;  // mult #overflows by 65636
   FreqCounter::f_freq += TCNTn; // add countern value

 FreqCounter::f_tics++; // count number of interrupt events
 if (TIFRn & 1) {    // if Timer/Counter n overflow flag
   FreqCounter::f_mlt++;   // count number of Countern overflows
   sbi(TIFRn,TOVn);  // clear Timer/Counter n overflow flag
 // PORTB = PORTB ^ 32;  // int activity test


replace the < and > with [ and ] to make the code tags work.
Avoid throwing electronics out as you or someone else might need them for parts or use.
Solid state rectifiers are the only REAL rectifiers.
Resistors for LEDS!

doug metzler

Thanks for the tip - I went back and edited.  I find it ironic that there are 35 buttons to put different smileys in the message but not one button to put code in the message.


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