Hi, I'm trying to make a circuit that uses the ATTiny85 to make a digital music box, that plays a song such as happy birthday. But currently, the loudspeaker plays the song very distortedly, such as static noises. Although you can hear the audio, it's very messy. I've tried implementing the recommended solutions like putting 100nF and 47uF capacitors but so far it hasn't worked at all. So, I'm not sure if I'm doing it right, or if there's another solution to this problem.
Here is the schematic diagram:
Here is what the actual project looks like (it still has my attempt of putting more capacitors to solve it):
And here is the code:
/* Digital Music Box v2
David Johnson-Davies - www.technoblogy.com - 16th March 2016
ATtiny85 @ 16 MHz (internal PLL; 4.3 V BOD)
CC BY 4.0
Licensed under a Creative Commons Attribution 4.0 International license:
http://creativecommons.org/licenses/by/4.0/
*/
int Scale[] = {
680, 721, 764, 809, 857, 908, 962, 1020, 1080, 1144, 1212, 1284,
1361, 1442, 1528, 1618, 1715, 1817, 1925, 2039, 2160, 2289, 2425, 2569,
2722, 2884, 3055, 3237, 3429, 3633, 3849, 4078 };
const int Channels = 4;
const int Tempo = 4; // 4 = 4 beats per second
const int Decay = 9; // Length of note decay; max 10
volatile unsigned int Acc[Channels];
volatile unsigned int Freq[Channels];
volatile unsigned int Amp[Channels];
// Play Happy Birthday
const uint32_t Tune[] PROGMEM = {
//_*_*__*_*_*__*_*__*_*_*__*_*__*_ff
//C D EF G A BC D EF G A BC D EF G
0b00000000000000000001000000000000,
0b00000000000000000001000000000000,
0b10000000000000000000010000000000,
0b00000000000000000000000000000000,
0b00001001000000000001000000000000,
0b00000000000000000000000000000000,
0b00000000000000000000000010000000,
0b00000000000000000000000000000000,
0b00100000000000000000000100000000,
0b00000000000000000000000000000000,
0b00000101000000000000000000000000,
0b00000000000000000000000000000000,
0b00000000000000000001000000000000,
0b00000000000000000001000000000000,
0b10000000000000000000010000000000,
0b00000000000000000000000000000000,
0b00000101000000000001000000000000,
0b00000000000000000000000000000000,
0b00000000000000000000000000100000,
0b00000000000000000000000000000000,
0b10000000000000000000000010000000,
0b00000000000000000000000000000000,
0b00001001000000000000000000000000,
0b00000000000000000000000000000000,
0b00000000000000000001000000000000,
0b00000000000000000001000000000000,
0b10000000000000000000000000000001,
0b00000000000000000000000000000000,
0b00100000000000000000000000001000,
0b00000000000000000000000000000000,
0b00001000000000000000000010000000,
0b00000000000000000000000000000000,
0b00000100000000000000000100000000,
0b00000000000000000000000000000000,
0b00000000000000000000010000000000,
0b00000000000000000000000000000000,
0b00000000000000000000000000000100,
0b00000000000000000000000000000100,
0b00000001000000000000000000001000,
0b00000000000000000000000000000000,
0b00000000000000000000000010000000,
0b00000000000000000000000000000000,
0b00000101000000000000000000100000,
0b00000000000000000000000000000000,
0b10001001000000000000000010000000,
0xFF}; // End of tune
//Globals persist throughout tune
int TunePtr = 0, Chan = 0;
// Watchdog interrupt plays notes
ISR(WDT_vect) {
sei(); // Allow interrupts
WDTCR |= 1<<WDIE;
unsigned long Chord = pgm_read_dword(&Tune[TunePtr]);
if (Chord == 0xFF) return;
TunePtr++;
// Read the bits in Chord
for (int Note = 0; Note < 32; Note++) {
if ((Chord & 0x80000000) != 0) {
Freq[Chan] = Scale[Note];
Amp[Chan] = 1<<(Decay+5);
Chan = (Chan + 1) % Channels;
}
Chord = Chord<<1;
}
}
// Generate square waves on 4 channels
ISR(TIMER0_COMPA_vect) {
signed char Temp, Mask, Env, Note, Sum=0;
for (int c = 0; c < Channels; c++) {
Acc[c] = Acc[c] + Freq[c];
Amp[c] = Amp[c] - (Amp[c] != 0);
Temp = Acc[c] >> 8;
Mask = Temp >> 7;
Env = Amp[c] >> Decay;
Note = (Env ^ Mask) + (Mask & 1);
Sum = Sum + Note;
}
OCR1B = Sum + 128;
}
void setup() {
// Enable 64 MHz PLL and use as source for Timer1
PLLCSR = 1<<PCKE | 1<<PLLE;
// Set up Timer/Counter1 for PWM output
TIMSK = 0; // Timer interrupts OFF
TCCR1 = 1<<CS10; // 1:1 prescale
GTCCR = 1<<PWM1B | 2<<COM1B0; // PWM B, clear on match
OCR1B = 128;
DDRB = 1<<DDB4; // Enable PWM output on pin 4
// Set up Timer/Counter0 for 20kHz interrupt to output samples.
TCCR0A = 3<<WGM00; // Fast PWM
TCCR0B = 1<<WGM02 | 2<<CS00; // 1/8 prescale
OCR0A = 99; // Divide by 100
TIMSK = 1<<OCIE0A; // Enable compare match, disable overflow
// Set up Watchdog timer for 4 Hz interrupt for note output.
WDTCR = 1<<WDIE | Tempo<<WDP0; // 4 Hz interrupt
}
void loop() {
}