Greetings,

Thanks a lot for answering, here is the code of autocorrelation.

By the way I tried with the RTTY library to make the FSK modem but it looks like it codes the fks in pulses :(. And plus the compiler had a problem on debug mode.

```
#include "C4.h"
// Sample Frequency in Hz
const float sample_freq = 22050;
int len = sizeof(rawData);
int i,k;
long sum, sum_old;
int thresh = 0;
float freq_per = 0;
byte pd_state = 0;
void setup() {
Serial.begin(115200);
sum = 0;
pd_state = 0;
int period = 0;
// Autocorrelation
for(i=0; i < len; i++)
{
sum_old = sum;
sum = 0;
for(k=0; k < len-i; k++) sum += (rawData[k]-128)*(rawData[k+i]-128)/256;
// Peak Detect State Machine
if (pd_state == 2 && (sum-sum_old) <=0)
{
period = i;
pd_state = 3;
}
if (pd_state == 1 && (sum > thresh) && (sum-sum_old) > 0) pd_state = 2;
if (!i) {
thresh = sum * 0.5;
pd_state = 1;
}
}
// Frequency identified in Hz
freq_per = sample_freq/period;
Serial.println(freq_per);
}
void loop() {
// put your main code here, to run repeatedly:
}
```

it also needed a source, in this case a pre made array was made with the data in it, i was thinking on capturing this data from an Analog input with a for routine, hoping that it will get enough data to make the sine wave array complete, but i am still not sure if the timming will be the right one, cause what i really care about is the frecuency, and the posibility that i can calculate it that way.

here is the C4.h library (which is just an array).

```
unsigned char rawData[970] = {
0x73, 0x7E, 0x3E, 0x39, 0xB0, 0x4D, 0x16, 0x48, 0x7C, 0xAB, 0x95, 0x9F,
0xA6, 0x47, 0x5E, 0x52, 0x28, 0x92, 0x9C, 0x9A, 0xDC, 0x90, 0x12, 0x7F,
0xE5, 0x94, 0x81, 0x79, 0x90, 0x5D, 0x48, 0x9B, 0xA9, 0xB5, 0x68, 0x56,
0x82, 0xA7, 0x5F, 0x74, 0xEB, 0x86, 0x4D, 0xB4, 0xAA, 0xAF, 0x74, 0x46,
0x99, 0xAD, 0x7D, 0x32, 0xCA, 0x8B, 0x63, 0xBF, 0x4D, 0x76, 0x78, 0x9A,
0xC9, 0x4D, 0xBB, 0xD9, 0x2E, 0x6E, 0x7B, 0x9B, 0xC4, 0x57, 0x79, 0x7F,
0x0D, 0x8B, 0xC8, 0x4F, 0xB2, 0x3F, 0x6F, 0xE1, 0x2A, 0x7E, 0xA6, 0x9E,
0x78, 0x6B, 0x64, 0x24, 0x99, 0x74, 0x1C, 0x3B, 0x6C, 0xA1, 0x9E, 0x96,
0xAB, 0x63, 0x4F, 0x62, 0x2C, 0x72, 0xA3, 0x92, 0xCA, 0xB2, 0x2E, 0x51,
0xD5, 0xAD, 0x81, 0x7C, 0x87, 0x75, 0x43, 0x86, 0xA5, 0xB4, 0x82, 0x54,
0x74, 0xA0, 0x7A, 0x5E, 0xCF, 0xAF, 0x4D, 0x96, 0xB3, 0xA8, 0x8F, 0x47,
0x82, 0xA9, 0x93, 0x3D, 0x97, 0xB4, 0x57, 0xB1, 0x70, 0x60, 0x82, 0x83,
0xC9, 0x6F, 0x88, 0xE9, 0x59, 0x51, 0x82, 0x86, 0xC3, 0x77, 0x63, 0x8C,
0x2B, 0x55, 0xCE, 0x68, 0x91, 0x72, 0x42, 0xDA, 0x5C, 0x56, 0xA7, 0x9C,
0x8A, 0x66, 0x71, 0x2F, 0x73, 0x90, 0x2E, 0x31, 0x5E, 0x93, 0xA2, 0x94,
0xA7, 0x7D, 0x4C, 0x64, 0x3B, 0x56, 0x9E, 0x94, 0xB5, 0xC3, 0x54, 0x37,
0xB5, 0xC1, 0x87, 0x7E, 0x81, 0x82, 0x4C, 0x6F, 0xA0, 0xAF, 0x96, 0x5C,
0x69, 0x94, 0x8C, 0x5C, 0xAC, 0xC7, 0x61, 0x7A, 0xB3, 0xA6, 0x9D, 0x57,
0x6B, 0xA2, 0x9E, 0x55, 0x6E, 0xBF, 0x67, 0x95, 0x8F, 0x57, 0x80, 0x7C,
0xB8, 0x92, 0x6D, 0xD9, 0x89, 0x43, 0x7D, 0x7F, 0xB4, 0x95, 0x5D, 0x88,
0x4D, 0x37, 0xB8, 0x8B, 0x77, 0x8F, 0x3C, 0xB4, 0x8F, 0x43, 0x99, 0x9D,
0x93, 0x6B, 0x72, 0x44, 0x55, 0x97, 0x49, 0x2B, 0x52, 0x84, 0xA1, 0x96,
0xA0, 0x90, 0x54, 0x5F, 0x4C, 0x45, 0x8E, 0x98, 0xA5, 0xC6, 0x79, 0x32,
0x8E, 0xC9, 0x94, 0x80, 0x7E, 0x85, 0x5C, 0x5E, 0x96, 0xA9, 0xA2, 0x6A,
0x61, 0x88, 0x95, 0x66, 0x8C, 0xCB, 0x7E, 0x67, 0xA8, 0xA8, 0xA2, 0x6C,
0x5D, 0x96, 0xA3, 0x6E, 0x59, 0xB3, 0x82, 0x7C, 0x9E, 0x5F, 0x75, 0x7C,
0xA2, 0xA8, 0x6A, 0xBB, 0xAF, 0x49, 0x6E, 0x7F, 0xA2, 0xA7, 0x65, 0x7B,
0x68, 0x31, 0x93, 0xA5, 0x6E, 0x94, 0x4E, 0x89, 0xAE, 0x4A, 0x81, 0xA0,
0x96, 0x76, 0x6F, 0x57, 0x45, 0x8C, 0x66, 0x2E, 0x47, 0x75, 0x9C, 0x99,
0x9A, 0x9A, 0x64, 0x59, 0x58, 0x41, 0x79, 0x9A, 0x9C, 0xBF, 0x97, 0x3F,
0x6C, 0xC1, 0xA3, 0x82, 0x7E, 0x84, 0x6C, 0x56, 0x87, 0xA4, 0xA7, 0x7B,
0x5F, 0x7C, 0x96, 0x74, 0x77, 0xC0, 0x99, 0x63, 0x96, 0xAB, 0xA3, 0x80,
0x5A, 0x86, 0xA2, 0x82, 0x55, 0x99, 0x9A, 0x72, 0x9C, 0x70, 0x6A, 0x7E,
0x92, 0xAF, 0x77, 0x9B, 0xC1, 0x60, 0x5F, 0x7E, 0x93, 0xAD, 0x76, 0x70,
0x77, 0x3B, 0x70, 0xAE, 0x76, 0x8B, 0x67, 0x69, 0xB3, 0x63, 0x6A, 0x9D,
0x98, 0x81, 0x6E, 0x64, 0x44, 0x78, 0x7A, 0x39, 0x3E, 0x68, 0x92, 0x9C,
0x97, 0x9C, 0x75, 0x58, 0x5D, 0x46, 0x66, 0x95, 0x98, 0xB4, 0xAA, 0x55,
0x55, 0xAE, 0xB0, 0x88, 0x7E, 0x82, 0x77, 0x58, 0x77, 0x9E, 0xA7, 0x8A,
0x63, 0x72, 0x91, 0x81, 0x6F, 0xAB, 0xAD, 0x6C, 0x84, 0xA9, 0xA3, 0x8D,
0x60, 0x76, 0x9D, 0x8F, 0x5E, 0x80, 0xA4, 0x76, 0x91, 0x82, 0x66, 0x7B,
0x88, 0xAB, 0x88, 0x86, 0xC0, 0x7E, 0x57, 0x79, 0x89, 0xA9, 0x89, 0x6B,
0x7B, 0x4D, 0x57, 0xA5, 0x87, 0x80, 0x7A, 0x5C, 0xA5, 0x7F, 0x5D, 0x93,
0x9A, 0x8A, 0x71, 0x6A, 0x4C, 0x65, 0x83, 0x4C, 0x3A, 0x5C, 0x87, 0x9B,
0x96, 0x9B, 0x84, 0x5D, 0x5E, 0x4E, 0x58, 0x8B, 0x97, 0xA9, 0xB2, 0x6F,
0x4C, 0x95, 0xB6, 0x91, 0x80, 0x81, 0x7D, 0x60, 0x6B, 0x94, 0xA5, 0x96,
0x6C, 0x6B, 0x89, 0x8A, 0x70, 0x96, 0xB4, 0x7C, 0x76, 0xA1, 0xA5, 0x96,
0x6C, 0x6B, 0x94, 0x97, 0x6C, 0x6F, 0xA2, 0x82, 0x85, 0x8D, 0x69, 0x76,
0x83, 0xA1, 0x97, 0x7D, 0xB2, 0x98, 0x5A, 0x70, 0x84, 0xA0, 0x97, 0x6F,
0x78, 0x5F, 0x4B, 0x92, 0x95, 0x7B, 0x82, 0x5F, 0x8F, 0x94, 0x5E, 0x83,
0x9A, 0x8F, 0x77, 0x6D, 0x56, 0x59, 0x81, 0x5F, 0x3B, 0x52, 0x7B, 0x97,
0x97, 0x99, 0x8E, 0x66, 0x5D, 0x56, 0x51, 0x7D, 0x96, 0xA0, 0xB2, 0x86,
0x4F, 0x7C, 0xB3, 0x9C, 0x83, 0x80, 0x80, 0x69, 0x64, 0x89, 0xA1, 0x9C,
0x78, 0x68, 0x80, 0x8D, 0x76, 0x86, 0xB1, 0x8E, 0x71, 0x96, 0xA5, 0x9B,
0x79, 0x66, 0x88, 0x99, 0x7A, 0x67, 0x95, 0x8F, 0x7E, 0x90, 0x72, 0x70,
0x7F, 0x96, 0x9F, 0x80, 0xA0, 0xA7, 0x67, 0x67, 0x7F, 0x96, 0x9E, 0x78,
0x74, 0x6C, 0x4C, 0x7C, 0x9C, 0x7E, 0x83, 0x68, 0x7B, 0x9C, 0x6A, 0x75,
0x97, 0x93, 0x7E, 0x6F, 0x60, 0x54, 0x78, 0x6F, 0x43, 0x4A, 0x70, 0x91,
0x98, 0x97, 0x93, 0x72, 0x5E, 0x5B, 0x51, 0x6F, 0x91, 0x9B, 0xAE, 0x97,
0x5B, 0x69, 0xA7, 0xA5, 0x88, 0x7F, 0x81, 0x72, 0x62, 0x7D, 0x9B, 0x9F,
0x83, 0x6A, 0x78, 0x8C, 0x7D, 0x7C, 0xA6, 0x9D, 0x74, 0x89, 0xA3, 0x9E,
0x85, 0x68, 0x7D, 0x97, 0x85, 0x68, 0x87, 0x96, 0x7E, 0x8C, 0x7C, 0x6E,
0x7C, 0x8E, 0xA0, 0x87, 0x91, 0xAC, 0x79, 0x62, 0x7A, 0x8E, 0x9F, 0x84,
0x72, 0x72, 0x53, 0x69, 0x99, 0x86, 0x81, 0x73, 0x6F, 0x98, 0x7A, 0x6B,
0x90, 0x96, 0x85, 0x73, 0x66, 0x55, 0x6D, 0x78, 0x4F, 0x46, 0x65, 0x88,
0x97, 0x96, 0x95, 0x7D, 0x62, 0x5E, 0x54, 0x64, 0x8A, 0x98, 0xA7, 0xA2,
0x6C, 0x5E, 0x96, 0xAA, 0x8F, 0x80, 0x80, 0x78, 0x65, 0x73, 0x94, 0x9F,
0x8D, 0x6F, 0x72, 0x87, 0x84, 0x78, 0x99, 0xA4, 0x7D, 0x7F, 0x9D, 0xA0,
0x8D, 0x6F, 0x74, 0x91, 0x8D, 0x6E, 0x7A, 0x96, 0x84, 0x87, 0x84, 0x6F,
0x78, 0x87, 0x9C, 0x90, 0x89, 0xA8, 0x8B, 0x64, 0x73, 0x88, 0x9B, 0x8E,
0x74, 0x74, 0x5E, 0x5D, 0x8E, 0x8E, 0x7F, 0x7A, 0x6C, 0x8E, 0x87, 0x6A,
0x85, 0x96, 0x8A, 0x77, 0x6B, 0x5A, 0x64, 0x79, 0x5C, 0x46, 0x5C, 0x7F,
0x94, 0x95, 0x95, 0x86, 0x69, 0x5F, 0x58, 0x5D, 0x80, 0x94, 0xA1, 0xA6,
0x7D, 0x5D, 0x84, 0xA8, 0x96, 0x83, 0x80, 0x7C, 0x6A, 0x6D, 0x8B, 0x9D,
0x94, 0x77, 0x6F, 0x81, 0x87, 0x7A, 0x8D, 0xA5, 0x89, 0x7A, 0x95, 0xA0,
0x94, 0x77, 0x6F, 0x89, 0x91, 0x77, 0x73, 0x91, 0x8A, 0x83, 0x88, 0x74,
0x74, 0x82, 0x96, 0x96, 0x87, 0x9F, 0x98, 0x6C, 0x6D, 0x82, 0x96, 0x94,
0x7A, 0x74, 0x67, 0x59, 0x80, 0x92, 0x81, 0x7D, 0x6E, 0x82, 0x8F, 0x6F,
0x7B, 0x93, 0x8E, 0x7D, 0x6F, 0x60, 0x5F, 0x76, 0x68, 0x4B, 0x54, 0x75,
0x8F, 0x95, 0x95, 0x8C, 0x71, 0x62, 0x5C, 0x5A, 0x76, 0x90, 0x9C, 0xA6,
0x8B, 0x62, 0x75, 0xA1, 0x9D, 0x87, 0x80, 0x7E, 0x70, 0x6A, 0x82, 0x99,
0x98, 0x7F, 0x6F, 0x7B, 0x87, 0x7D, 0x84, 0xA1, 0x92, 0x7C
};
```

Thank you so much for replaying, hope i can work this out; this is a very important developement i must do.

Have a great day.

Andrés.