PaulS:
Typos aside, this makes no sense. If you have one input, you have one output. I don’t know why you think one input should provide two outputs.
Sorry if Im being unclear. I meant that the audio signal oscilates around zero so if I have sine wave it goes above and below zero of the same value.
aarg:
Audio is a bipolar signal. It has a positive and a negative half. Rather than process a sign bit, we usually use two’s-complement to represent the signal. But, a DAC sometimes gives an unsigned range. All you need to do to convert the unsigned with an offset, to a signed with no offset, is subtract (for 8 bits in this case) 128. It also must then be stored in a signed data type.
Hi, sorry but could you expand on this a little bit? I am using someone elses code that has sampling rate of ~40kHz.
//variable to store incoming audio sample
byte incomingAudio;
//clipping indicator variables
boolean clipping = 0;
void setup(){
Serial.begin(9600);
pinMode(13,OUTPUT);//led indicator pin
cli();//disable interrupts
//set up continuous sampling of analog pin 0
//clear ADCSRA and ADCSRB registers
ADCSRA = 0;
ADCSRB = 0;
ADMUX |= (1 << REFS0); //set reference voltage
ADMUX |= (1 << ADLAR); //left align the ADC value- so we can read highest 8 bits from ADCH register only
ADCSRA |= (1 << ADPS2) | (1 << ADPS0); //set ADC clock with 32 prescaler- 16mHz/32=500kHz
ADCSRA |= (1 << ADATE); //enabble auto trigger
ADCSRA |= (1 << ADIE); //enable interrupts when measurement complete
ADCSRA |= (1 << ADEN); //enable ADC
ADCSRA |= (1 << ADSC); //start ADC measurements
sei();//enable interrupts
//if you want to add other things to setup(), do it here
}
ISR(ADC_vect) {//when new ADC value ready
incomingAudio = ADCH;//store 8 bit value from analog pin 0
if (incomingAudio == 0 || incomingAudio == 255){//if clipping
digitalWrite(13,HIGH);//set pin 13 high
clipping = 1;//currently clipping
}
}
void loop(){
Serial.print(incomingAudio);
Serial.println(" amp");
if (clipping){//if currently clipping
clipping = 0;//
digitalWrite(13,LOW);//turn off clipping led indicator (pin 13)
}
delay(100);
}
I am not really sure how to transfer your suggestion into this since the science behing bypassing of the function analogRead() is beyond my comprehension.
Thank you both for you suggestions!
