Locally declared variable takes up global variable space in dynamic memory/SRAM

Question

I'm trying to make my Arduino Uno control the air conditioner by recording the raw IR signal of several of the AC remotes temperatures using AnalysisIR. However these IR codes are quite long (array with 343 items).

Declaring more than one IR code in a variable shows me the error: "Global variables use 2064 bytes (100%) of dynamic memory, leaving -16 bytes for local variables. Maximum is 2048 bytes."

However, as seen in my code, I have declared the IR codes locally in a separate function to send them to the air conditioner. I don't understand why i get the error saying the global variables are taking up too much dynamic memory.

Isn't the space taken up by the local variable supposed to be freed up from the SRAM once the functions runs because I have declared the variable locally?

Thanks in advance.

Code:

#include <IRremote.h>


IRsend irsend;


int khz = 38;

void send23()
{

  unsigned int irSignal[]= {9048, 4496, 620, 1636, 620, 1636, 620, 520, 620, 520, 620, 524, 624, 524, 620, 532, 620, 1648, 620, 508, 620, 1640, 620, 1644, 620, 520, 620, 528, 616, 528, 620, 532, 624, 516, 620, 1636, 620, 516, 616, 520, 620, 520, 620, 524, 620, 528, 616, 536, 620, 520, 620, 508, 620, 1640, 620, 520, 620, 520, 620, 1648, 620, 1656, 620, 1656, 616, 524, 620, 508, 620, 516, 616, 520, 620, 520, 624, 520, 620, 528, 620, 532, 620, 520, 620, 508, 624, 508, 624, 516, 616, 520, 624, 524, 620, 524, 620, 532, 620, 504, 620, 7956, 616, 512, 620, 1640, 616, 520, 620, 520, 620, 524, 620, 528, 620, 528, 624, 1644, 620, 1636, 616, 1640, 624, 1640, 620, 1648, 616, 528, 620, 1652, 620, 532, 620, 520, 620, 512, 620, 512, 620, 516, 620, 524, 620, 524, 616, 528, 620, 532, 620, 520, 620, 508, 620, 512, 624, 512, 620, 520, 620, 520, 620, 528, 620, 532, 620, 520, 620, 508, 620, 516, 620, 516, 620, 520, 620, 524, 620, 524, 624, 528, 624, 516, 620, 508, 620, 512, 624, 512, 624, 516, 624, 520, 624, 524, 624, 528, 620, 520, 624, 504, 624, 512, 620, 516, 624, 516, 620, 524, 620, 524, 624, 528, 620, 520, 624, 504, 624, 1636, 624, 1640, 624, 1640, 624, 1648, 620, 524, 624, 1656, 624, 1624, 624, 7952, 616, 512, 624, 508, 624, 512, 624, 516, 624, 520, 624, 524, 624, 524, 624, 520, 624, 504, 624, 1636, 624, 512, 624, 516, 624, 520, 624, 524, 624, 524, 628, 516, 624, 504, 624, 508, 624, 512, 624, 516, 624, 520, 624, 524, 620, 528, 628, 512, 624, 508, 624, 508, 624, 512, 620, 520, 620, 524, 624, 520, 624, 528, 624, 516, 620, 508, 624, 508, 624, 512, 624, 1640, 624, 520, 624, 524, 624, 528, 624, 512, 628, 504, 624, 508, 624, 512, 624, 516, 624, 520, 624, 524, 624, 528, 624, 516, 620, 508, 624, 1632, 628, 508, 628, 1640, 624, 520, 624, 524, 620, 528, 624, 500, 608};
  irsend.sendRaw(irSignal, sizeof(irSignal) / sizeof(irSignal[0]), khz); //Note the approach used to automatically calculate the size of the array.
}

void send22()
{

  unsigned int irSignal[]=  {8988, 4548, 572, 1688, 572, 1688, 600, 532, 572, 568, 572, 572, 576, 572, 572, 580, 572, 1724, 544, 556, 576, 1684, 600, 1660, 608, 532, 604, 540, 608, 540, 600, 548, 608, 536, 604, 1652, 608, 520, 616, 524, 608, 532, 612, 532, 612, 532, 620, 532, 616, 524, 620, 512, 616, 1644, 624, 508, 628, 516, 624, 520, 628, 1676, 596, 1648, 632, 508, 632, 500, 632, 500, 632, 504, 636, 504, 636, 512, 628, 516, 632, 524, 628, 508, 636, 496, 632, 504, 628, 508, 632, 508, 632, 512, 632, 516, 632, 516, 632, 496, 628, 7948, 628, 500, 632, 1656, 600, 508, 628, 508, 632, 512, 632, 516, 632, 524, 628, 1636, 632, 496, 632, 504, 632, 504, 632, 508, 632, 1672, 600, 1672, 600, 520, 632, 508, 632, 500, 652, 480, 632, 504, 632, 512, 628, 512, 632, 516, 632, 520, 632, 508, 632, 496, 632, 504, 632, 504, 632, 508, 632, 516, 628, 520, 628, 520, 656, 484, 632, 500, 656, 476, 656, 480, 632, 508, 632, 516, 632, 512, 656, 496, 632, 508, 632, 500, 652, 480, 632, 504, 656, 484, 656, 488, 632, 516, 632, 520, 632, 508, 632, 500, 656, 476, 632, 508, 656, 484, 656, 488, 656, 492, 632, 520, 656, 484, 656, 1632, 624, 476, 632, 508, 656, 484, 656, 1620, 652, 488, 656, 1656, 600, 1648, 604, 7948, 656, 472, 656, 476, 660, 480, 632, 508, 656, 488, 652, 496, 656, 492, 656, 484, 632, 500, 656, 1608, 628, 504, 656, 484, 656, 488, 656, 492, 656, 496, 656, 484, 632, 496, 656, 480, 632, 504, 656, 484, 656, 488, 632, 516, 656, 496, 628, 508, 660, 472, 656, 480, 656, 480, 652, 488, 656, 488, 656, 492, 652, 496, 660, 484, 656, 472, 632, 504, 652, 484, 652, 1644, 624, 488, 656, 492, 656, 492, 632, 512, 628, 500, 664, 468, 656, 480, 656, 488, 652, 488, 656, 492, 656, 492, 632, 512, 652, 476, 656, 1632, 624, 484, 652, 1644, 620, 492, 656, 488, 628, 524, 652, 472, 608};
  irsend.sendRaw(irSignal, sizeof(irSignal) / sizeof(irSignal[0]), khz); //Note the approach used to automatically calculate the size of the array.
}

void setup()
{
  Serial.begin(9600);
  pinMode(13,OUTPUT);
  delay(2000);
  send23();
  delay(2000);
  send22();
}

void loop() {

}

EDIT 05/07:

Here is my new code with the use of PROGMEM.

As you can see, i have initialized the progmem arrays globally at the top of the program. When i do this, my SRAM is not full anymore but sendraw in the functions does not work anymore.

Weirdly however, when i declare the progmem variable INSIDE the send23() function (IN COMMENTS), the sendraw works! But the variable takes up space in the SRAM again and it says that Global variables have used 100% of dynamic memory.

Why does this happen and what can i do to work around it?

PROGMEM updated code:

#include <IRremote.h>

const unsigned int irSignal23[] PROGMEM = {9048, 4496, 620, 1636, 620, 1636, 620, 520, 620, 520, 620, 524, 624, 524, 620, 532, 620, 1648, 620, 508, 620, 1640, 620, 1644, 620, 520, 620, 528, 616, 528, 620, 532, 624, 516, 620, 1636, 620, 516, 616, 520, 620, 520, 620, 524, 620, 528, 616, 536, 620, 520, 620, 508, 620, 1640, 620, 520, 620, 520, 620, 1648, 620, 1656, 620, 1656, 616, 524, 620, 508, 620, 516, 616, 520, 620, 520, 624, 520, 620, 528, 620, 532, 620, 520, 620, 508, 624, 508, 624, 516, 616, 520, 624, 524, 620, 524, 620, 532, 620, 504, 620, 7956, 616, 512, 620, 1640, 616, 520, 620, 520, 620, 524, 620, 528, 620, 528, 624, 1644, 620, 1636, 616, 1640, 624, 1640, 620, 1648, 616, 528, 620, 1652, 620, 532, 620, 520, 620, 512, 620, 512, 620, 516, 620, 524, 620, 524, 616, 528, 620, 532, 620, 520, 620, 508, 620, 512, 624, 512, 620, 520, 620, 520, 620, 528, 620, 532, 620, 520, 620, 508, 620, 516, 620, 516, 620, 520, 620, 524, 620, 524, 624, 528, 624, 516, 620, 508, 620, 512, 624, 512, 624, 516, 624, 520, 624, 524, 624, 528, 620, 520, 624, 504, 624, 512, 620, 516, 624, 516, 620, 524, 620, 524, 624, 528, 620, 520, 624, 504, 624, 1636, 624, 1640, 624, 1640, 624, 1648, 620, 524, 624, 1656, 624, 1624, 624, 7952, 616, 512, 624, 508, 624, 512, 624, 516, 624, 520, 624, 524, 624, 524, 624, 520, 624, 504, 624, 1636, 624, 512, 624, 516, 624, 520, 624, 524, 624, 524, 628, 516, 624, 504, 624, 508, 624, 512, 624, 516, 624, 520, 624, 524, 620, 528, 628, 512, 624, 508, 624, 508, 624, 512, 620, 520, 620, 524, 624, 520, 624, 528, 624, 516, 620, 508, 624, 508, 624, 512, 624, 1640, 624, 520, 624, 524, 624, 528, 624, 512, 628, 504, 624, 508, 624, 512, 624, 516, 624, 520, 624, 524, 624, 528, 624, 516, 620, 508, 624, 1632, 628, 508, 628, 1640, 624, 520, 624, 524, 620, 528, 624, 500, 608};
const unsigned int irSignal22[] PROGMEM = {8988, 4548, 572, 1688, 572, 1688, 600, 532, 572, 568, 572, 572, 576, 572, 572, 580, 572, 1724, 544, 556, 576, 1684, 600, 1660, 608, 532, 604, 540, 608, 540, 600, 548, 608, 536, 604, 1652, 608, 520, 616, 524, 608, 532, 612, 532, 612, 532, 620, 532, 616, 524, 620, 512, 616, 1644, 624, 508, 628, 516, 624, 520, 628, 1676, 596, 1648, 632, 508, 632, 500, 632, 500, 632, 504, 636, 504, 636, 512, 628, 516, 632, 524, 628, 508, 636, 496, 632, 504, 628, 508, 632, 508, 632, 512, 632, 516, 632, 516, 632, 496, 628, 7948, 628, 500, 632, 1656, 600, 508, 628, 508, 632, 512, 632, 516, 632, 524, 628, 1636, 632, 496, 632, 504, 632, 504, 632, 508, 632, 1672, 600, 1672, 600, 520, 632, 508, 632, 500, 652, 480, 632, 504, 632, 512, 628, 512, 632, 516, 632, 520, 632, 508, 632, 496, 632, 504, 632, 504, 632, 508, 632, 516, 628, 520, 628, 520, 656, 484, 632, 500, 656, 476, 656, 480, 632, 508, 632, 516, 632, 512, 656, 496, 632, 508, 632, 500, 652, 480, 632, 504, 656, 484, 656, 488, 632, 516, 632, 520, 632, 508, 632, 500, 656, 476, 632, 508, 656, 484, 656, 488, 656, 492, 632, 520, 656, 484, 656, 1632, 624, 476, 632, 508, 656, 484, 656, 1620, 652, 488, 656, 1656, 600, 1648, 604, 7948, 656, 472, 656, 476, 660, 480, 632, 508, 656, 488, 652, 496, 656, 492, 656, 484, 632, 500, 656, 1608, 628, 504, 656, 484, 656, 488, 656, 492, 656, 496, 656, 484, 632, 496, 656, 480, 632, 504, 656, 484, 656, 488, 632, 516, 656, 496, 628, 508, 660, 472, 656, 480, 656, 480, 652, 488, 656, 488, 656, 492, 652, 496, 660, 484, 656, 472, 632, 504, 652, 484, 652, 1644, 624, 488, 656, 492, 656, 492, 632, 512, 628, 500, 664, 468, 656, 480, 656, 488, 652, 488, 656, 492, 656, 492, 632, 512, 652, 476, 656, 1632, 624, 484, 652, 1644, 620, 492, 656, 488, 628, 524, 652, 472, 608};
const unsigned int irSignal21[] PROGMEM = {9044, 4496, 624, 1628, 628, 1592, 668, 508, 628, 512, 628, 516, 628, 520, 628, 524, 628, 1636, 632, 500, 628, 1632, 624, 1636, 628, 512, 628, 520, 628, 516, 628, 524, 628, 512, 628, 1628, 628, 512, 620, 512, 624, 516, 628, 516, 628, 520, 628, 524, 628, 512, 628, 500, 632, 1628, 628, 512, 628, 512, 628, 1644, 628, 520, 628, 1648, 628, 512, 628, 504, 624, 508, 628, 508, 632, 508, 628, 516, 632, 516, 628, 524, 628, 512, 628, 504, 628, 504, 628, 508, 628, 512, 628, 516, 628, 520, 628, 524, 624, 500, 624, 7948, 628, 504, 628, 1628, 628, 512, 624, 516, 624, 516, 628, 520, 628, 524, 628, 1636, 628, 504, 624, 1632, 628, 508, 628, 512, 628, 1640, 628, 1648, 628, 520, 628, 512, 628, 504, 628, 504, 628, 508, 628, 512, 628, 516, 628, 516, 628, 524, 628, 512, 628, 500, 628, 504, 628, 508, 628, 512, 628, 516, 628, 520, 628, 520, 628, 512, 628, 500, 632, 504, 628, 508, 628, 512, 624, 520, 624, 520, 628, 524, 624, 516, 624, 504, 628, 504, 628, 508, 628, 512, 628, 516, 628, 520, 628, 520, 628, 512, 628, 504, 628, 504, 628, 508, 624, 516, 628, 512, 628, 520, 628, 524, 624, 516, 628, 1624, 628, 1632, 628, 508, 628, 512, 628, 516, 628, 1644, 628, 1648, 628, 1620, 628, 7944, 628, 500, 628, 504, 628, 512, 624, 512, 628, 516, 628, 520, 628, 520, 628, 512, 628, 504, 624, 1636, 624, 508, 632, 508, 628, 516, 628, 520, 628, 520, 632, 512, 624, 504, 628, 504, 628, 508, 628, 512, 628, 516, 628, 520, 628, 524, 624, 516, 628, 500, 628, 504, 628, 508, 628, 512, 628, 516, 628, 520, 628, 524, 624, 512, 628, 504, 624, 508, 628, 508, 628, 1640, 624, 516, 628, 520, 628, 524, 624, 516, 624, 504, 628, 504, 628, 508, 628, 512, 628, 516, 628, 520, 628, 524, 624, 512, 628, 504, 628, 1632, 624, 512, 628, 1640, 624, 516, 628, 520, 628, 524, 628, 492, 612};

IRsend irsend;

int khz = 38;

void send23()
{

//  const unsigned int irSignal23[] PROGMEM = {9048, 4496, 620, 1636, 620, 1636, 620, 520, 620, 520, 620, 524, 624, 524, 620, 532, 620, 1648, 620, 508, 620, 1640, 620, 1644, 620, 520, 620, 528, 616, 528, 620, 532, 624, 516, 620, 1636, 620, 516, 616, 520, 620, 520, 620, 524, 620, 528, 616, 536, 620, 520, 620, 508, 620, 1640, 620, 520, 620, 520, 620, 1648, 620, 1656, 620, 1656, 616, 524, 620, 508, 620, 516, 616, 520, 620, 520, 624, 520, 620, 528, 620, 532, 620, 520, 620, 508, 624, 508, 624, 516, 616, 520, 624, 524, 620, 524, 620, 532, 620, 504, 620, 7956, 616, 512, 620, 1640, 616, 520, 620, 520, 620, 524, 620, 528, 620, 528, 624, 1644, 620, 1636, 616, 1640, 624, 1640, 620, 1648, 616, 528, 620, 1652, 620, 532, 620, 520, 620, 512, 620, 512, 620, 516, 620, 524, 620, 524, 616, 528, 620, 532, 620, 520, 620, 508, 620, 512, 624, 512, 620, 520, 620, 520, 620, 528, 620, 532, 620, 520, 620, 508, 620, 516, 620, 516, 620, 520, 620, 524, 620, 524, 624, 528, 624, 516, 620, 508, 620, 512, 624, 512, 624, 516, 624, 520, 624, 524, 624, 528, 620, 520, 624, 504, 624, 512, 620, 516, 624, 516, 620, 524, 620, 524, 624, 528, 620, 520, 624, 504, 624, 1636, 624, 1640, 624, 1640, 624, 1648, 620, 524, 624, 1656, 624, 1624, 624, 7952, 616, 512, 624, 508, 624, 512, 624, 516, 624, 520, 624, 524, 624, 524, 624, 520, 624, 504, 624, 1636, 624, 512, 624, 516, 624, 520, 624, 524, 624, 524, 628, 516, 624, 504, 624, 508, 624, 512, 624, 516, 624, 520, 624, 524, 620, 528, 628, 512, 624, 508, 624, 508, 624, 512, 620, 520, 620, 524, 624, 520, 624, 528, 624, 516, 620, 508, 624, 508, 624, 512, 624, 1640, 624, 520, 624, 524, 624, 528, 624, 512, 628, 504, 624, 508, 624, 512, 624, 516, 624, 520, 624, 524, 624, 528, 624, 516, 620, 508, 624, 1632, 628, 508, 628, 1640, 624, 520, 624, 524, 620, 528, 624, 500, 608};
  irsend.sendRaw(irSignal23, sizeof(irSignal23) / sizeof(irSignal23[0]), khz); //Note the approach used to automatically calculate the size of the array.
}

void send22()
{
//  const unsigned int irSignal22[] PROGMEM = {8988, 4548, 572, 1688, 572, 1688, 600, 532, 572, 568, 572, 572, 576, 572, 572, 580, 572, 1724, 544, 556, 576, 1684, 600, 1660, 608, 532, 604, 540, 608, 540, 600, 548, 608, 536, 604, 1652, 608, 520, 616, 524, 608, 532, 612, 532, 612, 532, 620, 532, 616, 524, 620, 512, 616, 1644, 624, 508, 628, 516, 624, 520, 628, 1676, 596, 1648, 632, 508, 632, 500, 632, 500, 632, 504, 636, 504, 636, 512, 628, 516, 632, 524, 628, 508, 636, 496, 632, 504, 628, 508, 632, 508, 632, 512, 632, 516, 632, 516, 632, 496, 628, 7948, 628, 500, 632, 1656, 600, 508, 628, 508, 632, 512, 632, 516, 632, 524, 628, 1636, 632, 496, 632, 504, 632, 504, 632, 508, 632, 1672, 600, 1672, 600, 520, 632, 508, 632, 500, 652, 480, 632, 504, 632, 512, 628, 512, 632, 516, 632, 520, 632, 508, 632, 496, 632, 504, 632, 504, 632, 508, 632, 516, 628, 520, 628, 520, 656, 484, 632, 500, 656, 476, 656, 480, 632, 508, 632, 516, 632, 512, 656, 496, 632, 508, 632, 500, 652, 480, 632, 504, 656, 484, 656, 488, 632, 516, 632, 520, 632, 508, 632, 500, 656, 476, 632, 508, 656, 484, 656, 488, 656, 492, 632, 520, 656, 484, 656, 1632, 624, 476, 632, 508, 656, 484, 656, 1620, 652, 488, 656, 1656, 600, 1648, 604, 7948, 656, 472, 656, 476, 660, 480, 632, 508, 656, 488, 652, 496, 656, 492, 656, 484, 632, 500, 656, 1608, 628, 504, 656, 484, 656, 488, 656, 492, 656, 496, 656, 484, 632, 496, 656, 480, 632, 504, 656, 484, 656, 488, 632, 516, 656, 496, 628, 508, 660, 472, 656, 480, 656, 480, 652, 488, 656, 488, 656, 492, 652, 496, 660, 484, 656, 472, 632, 504, 652, 484, 652, 1644, 624, 488, 656, 492, 656, 492, 632, 512, 628, 500, 664, 468, 656, 480, 656, 488, 652, 488, 656, 492, 656, 492, 632, 512, 652, 476, 656, 1632, 624, 484, 652, 1644, 620, 492, 656, 488, 628, 524, 652, 472, 608};
  irsend.sendRaw(irSignal22, sizeof(irSignal22) / sizeof(irSignal22[0]), khz); //Note the approach used to automatically calculate the size of the array.
}

void send21()
{
//  const unsigned int irSignal21[] PROGMEM = {9044, 4496, 624, 1628, 628, 1592, 668, 508, 628, 512, 628, 516, 628, 520, 628, 524, 628, 1636, 632, 500, 628, 1632, 624, 1636, 628, 512, 628, 520, 628, 516, 628, 524, 628, 512, 628, 1628, 628, 512, 620, 512, 624, 516, 628, 516, 628, 520, 628, 524, 628, 512, 628, 500, 632, 1628, 628, 512, 628, 512, 628, 1644, 628, 520, 628, 1648, 628, 512, 628, 504, 624, 508, 628, 508, 632, 508, 628, 516, 632, 516, 628, 524, 628, 512, 628, 504, 628, 504, 628, 508, 628, 512, 628, 516, 628, 520, 628, 524, 624, 500, 624, 7948, 628, 504, 628, 1628, 628, 512, 624, 516, 624, 516, 628, 520, 628, 524, 628, 1636, 628, 504, 624, 1632, 628, 508, 628, 512, 628, 1640, 628, 1648, 628, 520, 628, 512, 628, 504, 628, 504, 628, 508, 628, 512, 628, 516, 628, 516, 628, 524, 628, 512, 628, 500, 628, 504, 628, 508, 628, 512, 628, 516, 628, 520, 628, 520, 628, 512, 628, 500, 632, 504, 628, 508, 628, 512, 624, 520, 624, 520, 628, 524, 624, 516, 624, 504, 628, 504, 628, 508, 628, 512, 628, 516, 628, 520, 628, 520, 628, 512, 628, 504, 628, 504, 628, 508, 624, 516, 628, 512, 628, 520, 628, 524, 624, 516, 628, 1624, 628, 1632, 628, 508, 628, 512, 628, 516, 628, 1644, 628, 1648, 628, 1620, 628, 7944, 628, 500, 628, 504, 628, 512, 624, 512, 628, 516, 628, 520, 628, 520, 628, 512, 628, 504, 624, 1636, 624, 508, 632, 508, 628, 516, 628, 520, 628, 520, 632, 512, 624, 504, 628, 504, 628, 508, 628, 512, 628, 516, 628, 520, 628, 524, 624, 516, 628, 500, 628, 504, 628, 508, 628, 512, 628, 516, 628, 520, 628, 524, 624, 512, 628, 504, 624, 508, 628, 508, 628, 1640, 624, 516, 628, 520, 628, 524, 624, 516, 624, 504, 628, 504, 628, 508, 628, 512, 628, 516, 628, 520, 628, 524, 624, 512, 628, 504, 628, 1632, 624, 512, 628, 1640, 624, 516, 628, 520, 628, 524, 628, 492, 612};
  irsend.sendRaw(irSignal21, sizeof(irSignal21) / sizeof(irSignal21[0]), khz); //Note the approach used to automatically calculate the size of the array.
}

void setup()
{
  Serial.begin(9600);
  pinMode(13, OUTPUT);
  send23();
  Serial.println("done");
  delay(4000);
  send22();
  Serial.println("done");
  delay(4000);
  send21();
  Serial.println("done");
}

void loop() {
}

The compiler can probably not be fooled that easy. I don't know how the compiler deals with it, perhaps someone else knows the answer. Do you really need integers? or is is a few different timings that could be put into a byte? I think you need an arduino board with more memory. Arrays of constant data belong in progmem: arduino.cc/reference/en/language/variables/utilities/progmem — Jot, Commented Jul 4, 2018 at 6:22
use PROGMEM arduino.cc/reference/en/language/variables/utilities/progmem — Juraj, Commented Jul 4, 2018 at 6:53
I tried using PROGMEM as well. However, if the const PROGMEM variable is declared inside the 'loop' function, it still takes up space in the SRAM. If the const PROGMEM variable is declared outside any function (globally), it no longer takes up space in the SRAM but the irRemote "sendRaw function no longer works." — ihish52, Commented Jul 4, 2018 at 7:18
make the PROGMEM array global and copy it to RAM in the function — Juraj, Commented Jul 4, 2018 at 8:59
Can you point me on how to copy the global PROGMEM array into my RAM during the functions execution? — ihish52, Commented Jul 5, 2018 at 6:54

Edgar Bonet · Accepted Answer · 2018-07-04 08:25:40Z

Isn't the space taken up by the local variable supposed to be freed up from the SRAM once the functions runs because I have declared the variable locally?

This is correct. The local arrays you have take up RAM only while the corresponding function is executing. They do not consume any static RAM (i.e. .data and .bss, what the Arduino IDE improperly calls “Global variables”).

The problem is not the arrays themselves, but rather the data used to initialize them. As an experiment, you can try to change the array definitions as follows:

unsigned int irSignal[343];

You will see the memory consumption reported by the IDE drop by 4×343 bytes. The local arrays are still there. They use RAM (from the stack) when the functions execute. Only you have removed the matching initializers.

I disassembled a slightly modified copy of your program just to see how the compiler handles it. I will not post the assembly code here, as I guess not many people here are fluent in AVR assembly. Instead, I will attempt to translate the assembly back to C in the most straightforward way. The compiler interpreted the function send23() as follows:

static const unsigned int anonymous_array_1[343] = {9048, ...};

void send23()
{
    unsigned int irSignal[343];
    for (int i = 0; i < 343; i++)
        irSignal[i] = anonymous_array_1[i];
    irsend.sendRaw(irSignal, 343, khz);
}

What is taking up static RAM is not the local arrays, it's the global anonymous arrays that hold the initialization data. You may notice that making the arrays local has actually worsened the problem: while send23() executes, you have two copies of the data in RAM.

The solution, as Jot and Juraj said in comments, is to put the arrays in PROGMEM. If it doesn't work, then you have a bug. You should fix the bug instead of trying to avoid PROGMEM.

Yes I have tried the progmem approach. Please see my edit on the post. I am guessing what i need to do now is to figure out how to copy the progmem variable into ram when the function runs? Perhaps that is why the send raw function is not working. — ihish52, Commented Jul 5, 2018 at 6:57
This is now very different from your original question. You should ask it as a new question. — Edgar Bonet, Commented Jul 5, 2018 at 7:26

ratchet freak · Accepted Answer · 2018-07-04 08:33:05Z

You must declare the array in global space or static, and make sure the function you pass the buffer pointer to knows it is in PROGMEM.

void send22()
{

  static unsigned int irSignal[] PROGMEM=  {8988, 4548, 572, 1688, 572, 1688, 600, 532, 572, 568, 572, 572, 576, 572, 572, 580, 572, 1724, 544, 556, 576, 1684, 600, 1660, 608, 532, 604, 540, 608, 540, 600, 548, 608, 536, 604, 1652, 608, 520, 616, 524, 608, 532, 612, 532, 612, 532, 620, 532, 616, 524, 620, 512, 616, 1644, 624, 508, 628, 516, 624, 520, 628, 1676, 596, 1648, 632, 508, 632, 500, 632, 500, 632, 504, 636, 504, 636, 512, 628, 516, 632, 524, 628, 508, 636, 496, 632, 504, 628, 508, 632, 508, 632, 512, 632, 516, 632, 516, 632, 496, 628, 7948, 628, 500, 632, 1656, 600, 508, 628, 508, 632, 512, 632, 516, 632, 524, 628, 1636, 632, 496, 632, 504, 632, 504, 632, 508, 632, 1672, 600, 1672, 600, 520, 632, 508, 632, 500, 652, 480, 632, 504, 632, 512, 628, 512, 632, 516, 632, 520, 632, 508, 632, 496, 632, 504, 632, 504, 632, 508, 632, 516, 628, 520, 628, 520, 656, 484, 632, 500, 656, 476, 656, 480, 632, 508, 632, 516, 632, 512, 656, 496, 632, 508, 632, 500, 652, 480, 632, 504, 656, 484, 656, 488, 632, 516, 632, 520, 632, 508, 632, 500, 656, 476, 632, 508, 656, 484, 656, 488, 656, 492, 632, 520, 656, 484, 656, 1632, 624, 476, 632, 508, 656, 484, 656, 1620, 652, 488, 656, 1656, 600, 1648, 604, 7948, 656, 472, 656, 476, 660, 480, 632, 508, 656, 488, 652, 496, 656, 492, 656, 484, 632, 500, 656, 1608, 628, 504, 656, 484, 656, 488, 656, 492, 656, 496, 656, 484, 632, 496, 656, 480, 632, 504, 656, 484, 656, 488, 632, 516, 656, 496, 628, 508, 660, 472, 656, 480, 656, 480, 652, 488, 656, 488, 656, 492, 652, 496, 660, 484, 656, 472, 632, 504, 652, 484, 652, 1644, 624, 488, 656, 492, 656, 492, 632, 512, 628, 500, 664, 468, 656, 480, 656, 488, 652, 488, 656, 492, 656, 492, 632, 512, 652, 476, 656, 1632, 624, 484, 652, 1644, 620, 492, 656, 488, 628, 524, 652, 472, 608};
  irsend.sendRaw_P(irSignal, sizeof(irSignal) / sizeof(irSignal[0]), khz); 
  // _P postfix is often used to mark functions taking in PROGMEM pointers
}

You can adjust the library to allow it to take PROGMEM buffers, with a quick search for the implementation of IRsend::sendRaw it gave me:

void  IRsend::sendRaw (const unsigned int buf[],  unsigned int len,  unsigned int hz)
{
    // Set IR carrier frequency
    enableIROut(hz);

    for (unsigned int i = 0;  i < len;  i++) {
        if (i & 1)  space(buf[i]) ;
        else        mark (buf[i]) ;
    }

    space(0);  // Always end with the LED off
}

To make it work with progmem you can create:

void  IRsend::sendRaw_P (const unsigned int buf[],  unsigned int len,  unsigned int hz)
{
    // Set IR carrier frequency
    enableIROut(hz);

    for (unsigned int i = 0;  i < len;  i++) {
        unsigned int word = pgm_read_word_near(buf + i);
        if (i & 1)  space(word) ;
        else        mark (word) ;
    }

    space(0);  // Always end with the LED off
}

How should i proceed to edit the existing IRremote library?
– ihish52
Commented Jul 5, 2018 at 6:56 — ihish52, Commented Jul 5, 2018 at 6:56

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