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/*
mh-timer.c -- simple functions for handling the Timer/Counter
Author : Ajith Kumar, Inter-University Accelerator Centre, New Delhi.
License : GNU GPL version 3 or later
Date : 23-Oct-2013
*/
#include <avr/io.h>
#include <avr/interrupt.h>
void sqwave_tc0(uint8_t csb, uint8_t ocrval)
{
// Set TCCR0 in the CTC mode
TCCR0 = (1 << WGM01) | (1 << COM00) | csb;
OCR0 = ocrval;
TCNT0 = 0;
DDRB |= (1 << PB3);
}
void pwm_tc0(uint8_t csb, uint8_t ocrval)
{
// Set TCCR0 in the Fast PWM mode
TCCR0 =(1 << WGM01) | (1 << WGM00) | (1 << COM01) | csb;
OCR0 = ocrval;
TCNT0 = 0;
DDRB |= (1 << PB3);
}
void sqwave_tc1(uint8_t csb, uint16_t ocra)
{
// This can set very low values of freqency on the output
TCCR1A = (1 << COM1A0); // Set TCCR1A in the CTC mode
TCCR1B = (1 << WGM12) | csb;
OCR1A = ocra; // Output Compare register values
TCNT1 = 0;
DDRD |= (1 << PD5); // Set pin OC1A as output
}
void pwm10_tc1(uint8_t csb, uint16_t ocra)
{
TCCR1A = (1 << COM1A1) | (1 << WGM11) |(1 << WGM10); // Set 10bit PWM mode
TCCR1B = csb;
OCR1A = ocra; // Output Compare register values
TCNT1 = 0;
DDRD |= (1 << PD5); // Set pin OC1A as output
}
//------------------------- Square wave on TC2 -------------------------
#define FLIMIT 4000000 // 8 MHz clock /2
static uint16_t f[] = {1,8,32,64,128,256,1024};
uint32_t set_sqr_tc2(uint32_t freq) // freq must be from 15 to 100000 Hz, no checking done
{
uint32_t tmp;
uint8_t ocr, k;
DDRD |= (1 << PD7); // Make PD7 as output
k = 0;
while(k < 7)
{
tmp = FLIMIT / f[k]; // maximum value for the chosen prescaler
if (tmp/freq <= 256)
{
TCCR2 = (1 << WGM21) | (1 << COM20) | (k+1); // CTC mode
ocr = tmp/freq;
tmp = tmp/ocr; // the value actually set
if (ocr)
--ocr;
OCR2 = ocr;
return tmp;
}
k = k + 1;
}
return 0;
}
//------------------- Frequency measurement ----------------------------
#define MTIME 250 // We count 100 on TC0
uint32_t measure_freq(void)
{
volatile uint16_t x, k = 500;
DDRB &= ~(1 << PB1); // Timer/Counter1 clock in T1 (PB1) as input
TCCR1B = (1 << CS12) | (1 << CS11) | (1 << CS10); // External clock on T1 pin
TCNT1 = 0; // Clear TCNT1
while(k--) {x=532; while (x--);}
TCCR1B = 0; // Stop counter
return TCNT1 * 2; // freq = Counts / 500 mS x 2
}
//----------------------- Time interval measurement--------------------------
volatile uint16_t HIWORD;
ISR(TIMER1_COMPA_vect) // TIMER1 Compare Match A Interrupt
{
TCNT1 = 0;
++HIWORD;
}
void start_timer()
{
/*
When TCNT1 reaches OCR1A, the ISR will run. It will clear TCNT1 and increment HIWORD.
The total time elapsed between start_timer and get_timer = HIWORD * 50000 + TCNT1
*/
TCCR1B = (1 << CS11); // Normal mode, with 1MHz clock
HIWORD = 0;
OCR1A = 50000;
OCR1B = 0xffff;
TIMSK = (1 << OCIE1A); // Enable compare match interrupt
TIFR = (1 << OCF1A);
TCNT1 = 0;
sei();
}
uint32_t read_timer()
{
uint32_t x;
TCCR1B = 0; // stop TC1 clock
x = HIWORD * 50000 + TCNT1;
cli();
return x;
}
uint32_t r2ftime(uint8_t bit)
{
// measures rising edge to falling edge time on any bit of PORTB. If no pulse input, program may go in infinite loop
DDRB &= ~(1 << bit); // set the selected bit as input, on PORT B
while( (PINB & (1 << bit)) != 0 ) ; // Do nothing until the bit is low
while( (PINB & (1 << bit)) == 0 ) ; // Wait for a rising edge
start_timer();
while( (PINB & (1 << bit)) != 0 ) ; // Wait for a falling edge
return read_timer();
}
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