130 lines
5.0 KiB
C++
130 lines
5.0 KiB
C++
/*
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FreqCounter.h -
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Using Counter1 for counting Frequency on T1 / PD5 / digitalPin 5
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Using Timer2 for Gatetime generation
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Martin Nawrath KHM LAB3
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Kunsthochschule für Medien Köln
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Academy of Media Arts
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http://www.khm.de
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http://interface.khm.de/index.php/labor/experimente/
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History:
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Dec/08 - V1.0
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Oct/10 - V1.1 removed occasional glitches through interference with
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Jan/12 - V1.2 Arduino 1.0
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timer0
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set intterrupt timebase to 1ms
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works with atmega328
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <FreqCounter.h>
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unsigned long FreqCounter::f_freq;
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volatile unsigned char FreqCounter::f_ready;
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volatile unsigned char FreqCounter::f_mlt;
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volatile unsigned int FreqCounter::f_tics;
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volatile unsigned int FreqCounter::f_period;
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volatile unsigned int FreqCounter::f_comp;
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void FreqCounter::start(int ms) {
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#if defined (__AVR_ATmega168__) || defined (__AVR_ATmega48__) || defined (__AVR_ATmega88__) || defined (__AVR_ATmega328P__) || (__AVR_ATmega1280__)
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TIMSK0 &=~(1<<TOIE0); // disable Timer0 //disable millis and delay
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delayMicroseconds(50); // wait if any ints are pending
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f_period=ms;
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if (f_comp ==0) f_comp=1; // 0 is not allowed in del us
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// hardware counter setup ( refer atmega168.pdf chapter 16-bit counter1)
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TCCR1A=0; // reset timer/counter1 control register A
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TCCR1B=0; // reset timer/counter1 control register A
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TCNT1=0; // counter value = 0
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// set timer/counter1 hardware as counter , counts events on pin T1 ( arduino pin 5)
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// normal mode, wgm10 .. wgm13 = 0
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TCCR1B |= (1<<CS10) ;// External clock source on T1 pin. Clock on rising edge.
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TCCR1B |= (1<<CS11) ;
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TCCR1B |= (1<<CS12) ;
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// timer2 setup / is used for frequency measurement gatetime generation
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TCCR2A=0;
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TCCR2B=0;
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// timer 2 presaler set to 128 / timer 2 clock = 16Mhz / 256 = 62500 Hz
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TCCR2B |= (1<<CS20) ;
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TCCR2B &= ~(1<<CS21) ;
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TCCR2B |= (1<<CS22) ;
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//set timer2 to CTC Mode with OCR2A is top counter value
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TCCR2A &= ~(1<<WGM20) ;
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TCCR2A |= (1<<WGM21) ;
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TCCR2A &= ~(1<<WGM22) ;
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OCR2A = 124; // CTC divider by 125
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f_ready=0; // reset period measure flag
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f_tics=0; // reset interrupt counter
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GTCCR = (1<<PSRASY); // reset presacler counting
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TCNT2=0; // timer2=0
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TCNT1=0; // Counter1 = 0
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TIMSK2 |=(1<<OCIE2A); // enable Timer2 Interrupt
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// External clock source on T1 pin. Clock on rising edge.
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TCCR1B |= (1<<CS12) | (1<<CS11) | (1<<CS10); // start counting now
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#endif
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}
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//******************************************************************
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// Timer2 Interrupt Service is invoked by hardware Timer2 every 1ms = 1000 Hz
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// 16Mhz / 128 / 125 = 1000 Hz
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// here the gatetime generation for freq. measurement takes place:
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ISR(TIMER2_COMPA_vect) {
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// multiple 2ms = gate time = 100 ms
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if (FreqCounter::f_tics >= FreqCounter::f_period) {
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// end of gate time, measurement ready
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// GateCalibration Value, set to zero error with reference frequency counter
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// delayMicroseconds(FreqCounter::f_comp); // 0.01=1/ 0.1=12 / 1=120 sec
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delayMicroseconds(FreqCounter::f_comp);
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TCCR1B = TCCR1B & ~7; // Gate Off / Counter T1 stopped
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TIMSK2 &= ~(1<<OCIE2A); // disable Timer2 Interrupt
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TIMSK0 |=(1<<TOIE0); // enable Timer0 again // millis and delay
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FreqCounter::f_ready=1; // set global flag for end count period
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// calculate now frequeny value
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FreqCounter::f_freq=0x10000 * FreqCounter::f_mlt; // mult #overflows by 65636
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FreqCounter::f_freq += TCNT1; // add counter1 value
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FreqCounter::f_mlt=0;
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}
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FreqCounter::f_tics++; // count number of interrupt events
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if (TIFR1 & 1) { // if Timer/Counter 1 overflow flag
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FreqCounter::f_mlt++; // count number of Counter1 overflows
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TIFR1 =(1<<TOV1); // clear Timer/Counter 1 overflow flag
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}
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// PORTB = PORTB ^ 32; // int activity test
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}
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