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//***************************************************************************
//* A P P L I C A T I O N N O T E F O R T H E A V R F A M I L Y
//*
//* Number : AVR314
//* File Name : "dtmf.c"
//* Title : DTMF Generator
//* Date : 00.06.27
//* Version : 1.0
//* Target MCU : Any AVR with SRAM, 8 I/O pins and PWM
//*
//* DESCRIPTION
//* This Application note describes how to generate DTMF tones using a single
//* 8 bit PWM output.
//*
//***************************************************************************
#include <stdio.h>
#define __IAR_SYSTEMS_ASM__
#include <io4414.h>
#include "ina90.h"
#define Xtal 8000000 // system clock frequency
#define prescaler 1 // timer1 prescaler
#define N_samples 128 // Number of samples in lookup table
#define Fck Xtal/prescaler // Timer1 working frequency
#define delaycyc 10 // port B setup delay cycles
//************************** SIN TABLE *************************************
// Samples table : one period sampled on 128 samples and
// quantized on 7 bit
//**************************************************************************
flash unsigned char auc_SinParam [128] = {
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 ***************************************
//Table of x_SW (excess 8): x_SW = ROUND(8*N_samples*f*510/Fck)
//**************************************************************************
//high frequency (coloun)
//1209hz ---> x_SW = 79
//1336hz ---> x_SW = 87
//1477hz ---> x_SW = 96
//1633hz ---> x_SW = 107
const unsigned char auc_frequencyH [4] = {
107,96,
87,79};
//low frequency (row)
//697hz ---> x_SW = 46
//770hz ---> x_SW = 50
//852hz ---> x_SW = 56
//941hz ---> x_SW = 61
const unsigned char auc_frequencyL [4] = {
61,56,
50,46};
//************************** global variables ****************************
unsigned char x_SWa = 0x00; // step width of high frequency
unsigned char x_SWb = 0x00; // step width of low frequency
unsigned int i_CurSinValA = 0; // position freq. A in LUT (extended format)
unsigned int i_CurSinValB = 0; // position freq. B in LUT (extended format)
unsigned int i_TmpSinValA; // position freq. A in LUT (actual position)
unsigned int i_TmpSinValB; // position freq. B in LUT (actual position)
//**************************************************************************
// Timer overflow interrupt service routine
//**************************************************************************
void interrupt [TIMER1_OVF1_vect] ISR_T1_Overflow (void)
{
// move Pointer about step width aheaed
i_CurSinValA += x_SWa;
i_CurSinValB += x_SWb;
// normalize Temp-Pointer
i_TmpSinValA = (char)(((i_CurSinValA+4) >> 3)&(0x007F));
i_TmpSinValB = (char)(((i_CurSinValB+4) >> 3)&(0x007F));
// calculate PWM value: high frequency value + 3/4 low frequency value
OCR1A = (auc_SinParam[i_TmpSinValA] + (auc_SinParam[i_TmpSinValB]-(auc_SinParam[i_TmpSinValB]>>2)));
}
//**************************************************************************
// Initialization
//**************************************************************************
void init (void)
{
TIMSK = 0x80; // Int T1 Overflow enabled
TCCR1A = (1<<COM1A1)+(1<<PWM10); // non inverting / 8Bit PWM
TCCR1B = (1<<CS10); // CLK/1
DDRD = (1 << PD5); // PD5 (OC1A) as output
_SEI(); // Interrupts enabled
}
//**************************************************************************
// Time delay to ensure a correct setting of the pins of Port B
//**************************************************************************
void Delay (void)
{
int i;
for (i = 0; i < delaycyc; i++) _NOP();
}
//**************************************************************************
// MAIN
// Read from portB (eg: using evaluation board switch) which
// tone to generate, extract mixing high frequency
// (column) and low frequency (row), and then
// fix x_SWa and x_SWb
// row -> PINB high nibble
// column -> PINB low nibble
//**************************************************************************
void main (void)
{
unsigned char uc_Input;
unsigned char uc_Counter = 0;
init();
for(;;){
// high nibble - rows
DDRB = 0x0F; // high nibble input / low nibble output
PORTB = 0xF0; // high nibble pull up / low nibble low value
uc_Counter = 0;
Delay(); // wait for Port B lines to be set up correctly
uc_Input = PINB; // read Port B
do
{
if(!(uc_Input & 0x80)) // check if MSB is low
{
// if yes get step width and end loop
x_SWb = auc_frequencyL[uc_Counter];
uc_Counter = 4;
}
else
{
x_SWb = 0; // no frequency modulation needed
}
uc_Counter++;
uc_Input = uc_Input << 1; // shift Bits one left
} while ((uc_Counter < 4));
// low nibble - columns
DDRB = 0xF0; // high nibble output / low nibble input
PORTB = 0x0F; // high nibble low value / low nibble pull up
uc_Counter = 0;
Delay(); // wait for Port B lines to be set up correctly
uc_Input = PINB;
uc_Input = uc_Input << 4;
do
{
if(!(uc_Input & 0x80)) // check if MSB is low
{
// if yes get delay and end loop
x_SWa = auc_frequencyH[uc_Counter];
uc_Counter = 4;
}
else
{
x_SWa = 0;
}
uc_Counter++;
uc_Input = uc_Input << 1;
} while (uc_Counter < 4);
}
}
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