Datalogging: Sound --- Array Storage Issues

Thanks in advance to those who reply.

I am very new to Arduino. I have set the clock with a prescalar of 32 to allow an interrupt to occur at ~38.5 kHz. I would like to store the data gathered by the ADCH in the interrupt into an array that can be read later to an SD card. Essentially, there is a short burst of data that must be written/stored and then a long time in between in which the SD card can write to file.


— The array size will not go over 500. This is the primary issue I would like to fix and have been thus far, unable.
— The time stamp fails to synchronize with the serial port (the computer).

Thank you for any help.

//communication for the RTC
#define DS1307_I2C_ADDRESS 0x68
#include <SD.h>
#include <RTClib.h>
#include <Wire.h>
//defining the variables
const int chipSelect = 10;
int z=0, dg = 1, s_s = 100, arr_in[100], input;
RTC_DS1307 RTC; // initializing the library to be called by RTC

/* z functions as index for the data array (arr_in [z]), dg is set as flag for datagathering status, s_s is the sample size which is the largest storage in the data array, input is the middleman variable in between the ADCH and the array */
void setup() {
// initialize serial communication at 115200 bits per second:
pinMode(10, OUTPUT);
//intializing SD card
if (!SD.begin(chipSelect)) {
Serial.println(“no card”);
Serial.println(“yes card”);
//initializing time stamp
RTC.begin ();
if (!RTC.begin()) {
Serial.println (“Time not set”);
RTC.adjust(DateTime(DATE, TIME));

Serial.println (“Time set”);
delay (100);

cli (); //disables interrupts
//set up continuous sampling of analog pin 0
//clear ADCSRA and ADCSRB registers
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 or free running mode
ADCSRA |= (1 << ADIE); //enable interrupts when measurement complete
ADCSRA |= (1 << ADEN); //enable ADC
ADCSRA |= (1 << ADSC); //start ADC measurements
sei();//sets interrupts


ISR(ADC_vect) {//when new ADC value ready
if (z == s_s) { //checking for full buffer arry
dg = 0;
cli ();

if (z < s_s) {
dg = 1;
input = ADCH;
arr_in[z] = input;


void loop () {

DateTime now = ();
//data gathering switched off
if (dg == 0){
for (z=0;z<s_s;z++) {

File logFile = (“logFile.csv”, FILE_WRITE);
if (!logFile) {
Serial.println(“false file”);
if (logFile){
logFile.print(now.month(), DEC);
logFile.print(, DEC);
logFile.print(now.year(), DEC);
logFile.print(",");//move to next Excel cell for time stamp
//time stamp
logFile.print(now.hour(), DEC);
logFile.print(now.minute(), DEC);
logFile.println(arr_in [z]);
logFile.close ();

dg = 1;
z = 0;
sei ();



The Arduino only has 2K of SRAM.

SD.h, Wire, and Serial use 800-900 bytes. 500 ints uses another 1000 bytes. That's uses all of your RAM..

You should store ADCH in a uint8_t array. Then you could have almost 1000 entries.

Also put print strings in flash memory by using the F() macro like this:

  Serial.println(F("yes card"));

Thanks for the help!