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dtmf.c
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//*****************************************************************************
// Title : Pulse to tone (DTMF) converter
// Author : Boris Cherkasskiy
// http://boris0.blogspot.ca/2013/09/rotary-dial-for-digital-age.html
// Created : 2011-10-24
//
// Modified : Arnie Weber 2015-06-22
// https://bitbucket.org/310weber/rotary_dial/
// NOTE: This code is not compatible with Boris's original hardware
// due to changed pin-out (see Eagle files for details)
//
// Modified : Matthew Millman 2018-05-29
// http://tech.mattmillman.com/
// Cleaned up implementation, modified to work more like the
// Rotatone product.
//
// This code is distributed under the GNU Public License
// which can be found at http://www.gnu.org/licenses/gpl.txt
//
// DTMF generator logic is loosely based on the AVR314 app note from Atmel
//
//*****************************************************************************
#include <stdbool.h>
#include <stdint.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include "dtmf.h"
#define TIMER_CLK_DIV1 0x01 ///< Timer clocked at F_CPU
#define TIMER_PRESCALE_MASK0 0x07 ///< Timer Prescaler Bit-Mask
#define NUM_SAMPLES 128 // Number of samples in lookup table
static void dtmf_enable_pwm(void);
//************************** SIN TABLE *************************************
// Samples table : one period sampled on 128 samples and
// quantized on 7 bit
//**************************************************************************
const uint8_t auc_sin_param[NUM_SAMPLES] = {
64, 67, 70, 73,
76, 79, 82, 85,
88, 91, 94, 96,
99, 102, 104, 106,
109, 111, 113, 115,
117, 118, 120, 121,
123, 124, 125, 126,
126, 127, 127, 127,
127, 127, 127, 127,
126, 126, 125, 124,
123, 121, 120, 118,
117, 115, 113, 111,
109, 106, 104, 102,
99, 96, 94, 91,
88, 85, 82, 79,
76, 73, 70, 67,
64, 60, 57, 54,
51, 48, 45, 42,
39, 36, 33, 31,
28, 25, 23, 21,
18, 16, 14, 12,
10, 9, 7, 6,
4, 3, 2, 1,
1, 0, 0, 0,
0, 0, 0, 0,
1, 1, 2, 3,
4, 6, 7, 9,
10, 12, 14, 16,
18, 21, 23, 25,
28, 31, 33, 36,
39, 42, 45, 48,
51, 54, 57, 60
};
//*************************** x_SW ***************************************
// Fck = Xtal/prescaler
// Table of x_SW (excess 8): x_SW = ROUND(8 * N_samples * f * 510 / Fck)
//**************************************************************************
// high frequency
// 1209hz ---> x_SW = 79
// 1336hz ---> x_SW = 87
// 1477hz ---> x_SW = 96
// 1633hz ---> x_SW = 107
//
// low frequency
// 697hz ---> x_SW = 46
// 770hz ---> x_SW = 50
// 852hz ---> x_SW = 56
// 941hz ---> x_SW = 61
//
// | 1209 | 1336 | 1477 | 1633
// 697 | 1 | 2 | 3 | A
// 770 | 4 | 5 | 6 | B
// 852 | 7 | 8 | 9 | C
// 941 | * | 0 | # | D
const uint8_t auc_frequency[12][2] =
{
{ 87, 61 }, // 0
{ 79, 46 }, // 1
{ 87, 46 }, // 2
{ 96, 46 }, // 3
{ 79, 50 }, // 4
{ 87, 50 }, // 5
{ 96, 50 }, // 6
{ 79, 56 }, // 7
{ 87, 56 }, // 8
{ 96, 56 }, // 9
{ 79, 61 }, // *
{ 96, 61 }, // #
};
volatile uint32_t _g_delay_counter; // Delay counter for sleep function
volatile uint8_t _g_stepwidth_a; // step width of high frequency
volatile uint8_t _g_stepwidth_b; // step width of low frequency
volatile uint16_t _g_cur_sin_val_a; // position freq. A in LUT (extended format)
volatile uint16_t _g_cur_sin_val_b; // position freq. B in LUT (extended format)
void dtmf_init(void)
{
TIMSK = _BV(TOIE0); // Int T0 Overflow enabled
TCCR0A = _BV(WGM00) | _BV(WGM01); // 8Bit PWM; Compare/match output mode configured later
TCCR0B = TIMER_PRESCALE_MASK0 & TIMER_CLK_DIV1;
TCNT0 = 0;
OCR0A = 0;
DDRB |= _BV(PIN_PWM_OUT); // PWM output (OC0A pin)
_g_stepwidth_a = 0x00;
_g_stepwidth_b = 0x00;
_g_cur_sin_val_a = 0;
_g_cur_sin_val_b = 0;
_g_delay_counter = 0;
}
// Generate DTMF tone, duration x ms
void dtmf_generate_tone(int8_t digit, uint16_t duration_ms)
{
GIMSK = 0;
if (digit >= 0 && digit <= DIGIT_POUND)
{
// Standard digits 0-9, *, #
_g_stepwidth_a = auc_frequency[digit][0];
_g_stepwidth_b = auc_frequency[digit][1];
dtmf_enable_pwm();
// Wait x ms
sleep_ms(duration_ms);
}
else if (digit == DIGIT_BEEP)
{
// Beep ~1000Hz (66)
_g_stepwidth_a = 66;
_g_stepwidth_b = 0;
dtmf_enable_pwm();
// Wait x ms
sleep_ms(duration_ms);
}
else if (digit == DIGIT_BEEP_LOW)
{
// Beep ~500Hz (33)
_g_stepwidth_a = 33;
_g_stepwidth_b = 0;
dtmf_enable_pwm();
// Wait x ms
sleep_ms(duration_ms);
}
else if (digit == DIGIT_TUNE_ASC)
{
_g_stepwidth_a = 34; // C=523.25Hz
_g_stepwidth_b = 0;
dtmf_enable_pwm();
sleep_ms(duration_ms / 3);
_g_stepwidth_a = 43; // E=659.26Hz
sleep_ms(duration_ms / 3);
_g_stepwidth_a = 51; // G=784Hz
sleep_ms(duration_ms / 3);
}
else if (digit == DIGIT_TUNE_DESC)
{
_g_stepwidth_a = 51; // G=784Hz
_g_stepwidth_b = 0;
dtmf_enable_pwm();
sleep_ms(duration_ms / 3);
_g_stepwidth_a = 43; // E=659.26Hz
sleep_ms(duration_ms / 3);
_g_stepwidth_a = 34; // C=523.25Hz
sleep_ms(duration_ms / 3);
}
// Stop DTMF transmitting
// Disable PWM output (compare match mode 0) and force it to 0
TCCR0A &= ~_BV(COM0A1);
TCCR0A &= ~_BV(COM0A0);
PORTB &= ~_BV(PIN_PWM_OUT);
_g_stepwidth_a = 0;
_g_stepwidth_b = 0;
GIMSK = _BV(INT0) | _BV(PCIE);
}
// Enable PWM output by configuring compare match mode - non inverting PWM
static void dtmf_enable_pwm(void)
{
TCCR0A |= _BV(COM0A1);
TCCR0A &= ~_BV(COM0A0);
}
// Timer overflow interrupt service routine
ISR(TIMER0_OVF_vect)
{
uint8_t sin_a;
uint8_t sin_b;
// A component (high frequency) is always used
// move Pointer about step width ahead
_g_cur_sin_val_a += _g_stepwidth_a;
// normalize Temp-Pointer
uint16_t tmp_sin_val_a = (int8_t)(((_g_cur_sin_val_a + 4) >> 3) & (0x007F));
sin_a = auc_sin_param[tmp_sin_val_a];
// B component (low frequency) is optional
if (_g_stepwidth_b > 0)
{
// move Pointer about step width ahead
_g_cur_sin_val_b += _g_stepwidth_b;
// normalize Temp-Pointer
uint16_t tmp_sin_val_b = (int8_t)(((_g_cur_sin_val_b + 4) >> 3) & (0x007F));
sin_b = auc_sin_param[tmp_sin_val_b];
}
else
{
sin_b = 0;
}
// calculate PWM value: high frequency value + 3/4 low frequency value
OCR0A = (sin_a + (sin_b - (sin_b >> 2)));
_g_delay_counter++;
}
// Wait x ms
void sleep_ms(uint16_t msec)
{
_g_delay_counter = 0;
set_sleep_mode(SLEEP_MODE_IDLE);
while(_g_delay_counter <= msec * T0_OVERFLOW_PER_MS)
{
sleep_mode();
}
}