How can i reduce my global variable use? Attiny85

Question

I'm trying to compile my code but i keep exceeding my global variable memory by 12%. Is there anything i can do in my code to further reduce RAM usage? Or do i have to do modifications to the libraries I'm using? Here is my main program:

    #include <MIDI.h>
#include <FastLED.h>
#include <SoftwareSerial.h>

#define LED_PIN 3
#define NUM_LEDS 60
#define LEDMAP 0xAB5AB5AB5AB5AB5
#define OFFSET 36
#define RANGECHECK if (pitch > 35 && pitch < 96)

SoftwareSerial softSerial(2, 4);
CRGB leds[NUM_LEDS];

MIDI_CREATE_INSTANCE(SoftwareSerial, softSerial, midiB);

void setup() {
  FastLED.addLeds<WS2811, LED_PIN, GRB>(leds, NUM_LEDS);
  FastLED.clear(true);
  midiB.begin(MIDI_CHANNEL_OMNI);
  midiB.setHandleNoteOn(HandleOn);
  midiB.setHandleNoteOff(HandleOff);
}

void loop() {
  midiB.read();
}

void HandleOn(byte channel, byte pitch, byte velocity)
{
  RANGECHECK
  {
    leds[pitch - OFFSET] = bitRead(LEDMAP, (pitch - OFFSET)) ? CRGB::NavajoWhite : CRGB::Salmon;
    FastLED.show();
  }
}

void HandleOff(byte channel, byte pitch, byte velocity)
{
  RANGECHECK
  {
    leds[pitch - OFFSET] = CRGB::Black;
    FastLED.show();
  }
}

I've reached my limit in optimizing my RAM usage here. Any suggestions for optimizing my code would be appreciated.

Answer 1

FastLED needs to keep the colors of all the pixel in RAM, so that is using a lot of RAM.

To get around this, you could use a strategy that generates the pixel data on the fly as you send it out to the strings. Here is an example of a project that does that...

https://wp.josh.com/2021/04/21/build-a-live-scrolling-tickertape/

Also, SoftSerial keeps a buffer (looks like 64 bytes?) which also uses some RAM. You could use a different approach to serial communications that does not allocate such a large buffer. It would take work, but you could even process the midi bytes as they were received and not need any byte buffer.

Answer 2

Since i don't use sysex messages, i got my RAM usage down to 84% by setting the SysExMaxSize

in midi_settings.h to 0.