PaulS:
You assign a value to PressStatus, in loop(). You check that value in the interrupt service routine, but you have not declared that PressStatus is volatile. So, the compiler is likely optimizing code out of existence.I'll admit that I don't understand all that stuff in startPlayback(), but I suspect that you ISR is not doing what you think it does (because PressStatus is not volatile).
Hi Pauls,
I have change my code, changed the PressStatus as volatile. do you think the code is OK?
#include <stdint.h>
#include <avr/interrupt.h>
#include <avr/io.h>
#include <avr/pgmspace.h>
#define SAMPLE_RATE 8000/2 //control the frequency of the output signal =16M/SAMPLE_RATE/256
int outputPin = 6; // (PCINT22/OC0A/AIN0)PD6, Arduino Digital Pin 6
volatile uint16_t sample;
const int sinewave_length=256;
int led =13;
float voltageValue[10];
float voltage[10];
volatile int PressStatus;//Pressing flag;
const unsigned char sinewave_data[] PROGMEM = {
0x80,0x83,0x86,0x89,0x8c,0x8f,0x92,0x95,0x98,0x9c,0x9f,0xa2,0xa5,0xa8,0xab,0xae,
0xb0,0xb3,0xb6,0xb9,0xbc,0xbf,0xc1,0xc4,0xc7,0xc9,0xcc,0xce,0xd1,0xd3,0xd5,0xd8,
0xda,0xdc,0xde,0xe0,0xe2,0xe4,0xe6,0xe8,0xea,0xec,0xed,0xef,0xf0,0xf2,0xf3,0xf5,
0xf6,0xf7,0xf8,0xf9,0xfa,0xfb,0xfc,0xfc,0xfd,0xfe,0xfe,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xfe,0xfe,0xfd,0xfc,0xfc,0xfb,0xfa,0xf9,0xf8,0xf7,
0xf6,0xf5,0xf3,0xf2,0xf0,0xef,0xed,0xec,0xea,0xe8,0xe6,0xe4,0xe2,0xe0,0xde,0xdc,
0xda,0xd8,0xd5,0xd3,0xd1,0xce,0xcc,0xc9,0xc7,0xc4,0xc1,0xbf,0xbc,0xb9,0xb6,0xb3,
0xb0,0xae,0xab,0xa8,0xa5,0xa2,0x9f,0x9c,0x98,0x95,0x92,0x8f,0x8c,0x89,0x86,0x83,
0x80,0x7c,0x79,0x76,0x73,0x70,0x6d,0x6a,0x67,0x63,0x60,0x5d,0x5a,0x57,0x54,0x51,
0x4f,0x4c,0x49,0x46,0x43,0x40,0x3e,0x3b,0x38,0x36,0x33,0x31,0x2e,0x2c,0x2a,0x27,
0x25,0x23,0x21,0x1f,0x1d,0x1b,0x19,0x17,0x15,0x13,0x12,0x10,0x0f,0x0d,0x0c,0x0a,
0x09,0x08,0x07,0x06,0x05,0x04,0x03,0x03,0x02,0x01,0x01,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x01,0x02,0x03,0x03,0x04,0x05,0x06,0x07,0x08,
0x09,0x0a,0x0c,0x0d,0x0f,0x10,0x12,0x13,0x15,0x17,0x19,0x1b,0x1d,0x1f,0x21,0x23,
0x25,0x27,0x2a,0x2c,0x2e,0x31,0x33,0x36,0x38,0x3b,0x3e,0x40,0x43,0x46,0x49,0x4c,
0x4f,0x51,0x54,0x57,0x5a,0x5d,0x60,0x63,0x67,0x6a,0x6d,0x70,0x73,0x76,0x79,0x7c};
void startPlayback()
{
pinMode(outputPin, OUTPUT);
// Set Timer 0 Fast PWM Mode
// WGM = 0b011 = 3 (Table 14-8)
// TOP = 0xFF, update OCR0A register at BOTTOM
TCCR0A |= _BV(WGM01) | _BV(WGM00);
TCCR0B &= ~_BV(WGM02);
// Do non-inverting PWM on pin OC0A, arduino digital pin 6
// COM0A = 0b10, clear OC0A pin on compare match,
// set 0C0A pin at BOTTOM (Table 14-3)
TCCR0A = (TCCR0A | _BV(COM0A1)) & ~_BV(COM0A0);
// COM0B = 0b00, OC0B disconnected (Table 14-6)
TCCR0A &= ~(_BV(COM0B1) | _BV(COM0B0));
// No prescaler, CS = 0b001 (Table 14-9)
TCCR0B = (TCCR0B & ~(_BV(CS02) | _BV(CS01))) | _BV(CS00);
// Set initial pulse width to the first sample.
OCR0A = pgm_read_byte(&sinewave_data[0]);
// Set up Timer 1 to send a sample every interrupt.
cli(); // disable interrupts
// Set CTC mode (Section 15.9.2 Clear Timer on Compare Match)
// WGM = 0b0100, TOP = OCR1A, Update 0CR1A Immediate (Table 15-4)
// Have to set OCR1A *after*, otherwise it gets reset to 0!
TCCR1B = (TCCR1B & ~_BV(WGM13)) | _BV(WGM12);
TCCR1A = TCCR1A & ~(_BV(WGM11) | _BV(WGM10));
// No prescaler, CS = 0b001 (Table 15-5)
TCCR1B = (TCCR1B & ~(_BV(CS12) | _BV(CS11))) | _BV(CS10);
// Set the compare register (OCR1A).
// OCR1A is a 16-bit register, so we have to do this with
// interrupts disabled to be safe.
OCR1A = F_CPU / SAMPLE_RATE; // 16e6 / 8000 = 2000
// Enable interrupt when TCNT1 == OCR1A (p.136)
TIMSK1 |= _BV(OCIE1A);
sample = 0;
sei(); // enable interrupts
}
void setup()
{
startPlayback();
//initialize serial communication at 4800bit per second;
Serial.begin(4800);
pinMode (led,OUTPUT);
}
void loop()
{
int i;
for(i=0;i<10;i++){
voltageValue[i] = analogRead(A0);
voltage[i] = voltageValue[i] * (5.0 / 1023.0);
if (i>0&&voltage[i]-voltage[i-1]>=0.2){
PressStatus=1;
digitalWrite(led,HIGH);
}
else {
PressStatus=0;
digitalWrite(led,LOW);
}
}
}
// This is called at SAMPLE_RATE kHz to load the next sample.
ISR(TIMER1_COMPA_vect) {
if ((sample < sinewave_length)&&(PressStatus==1)) {
OCR0A = pgm_read_byte(&sinewave_data[sample]);
}
else {
sample = -1;
}
++sample;
}