Low memory warning on compile?

Projects Programming
1

I get the following message after compiling my code:

Sketch uses 10,296 bytes (31%) of program storage space. Maximum is 32,256 bytes.
Global variables use 1,826 bytes (89%) of dynamic memory, leaving 222 bytes for local variables. Maximum is 2,048 bytes.
Low memory available, stability problems may occur.

Is this "Low memory" a result of too many global variables? I could probably switch some of them to local variables, but would that help?

2

May help some.
Might be more helpful to put things that don't change into flash memory instead. Font definitions, messages to display on a screen, look up tables ...
Review your variable declarations also - all too often int is used when byte would do (value is <=255).

3

Moving them to local variables would help in most cases as they only use memory when actively used.

  • use local variables where possible

  • use smallest datatype possible

  • byte = 1 byte

  • int = 2 bytes

  • long/float = 4 bytes

  • if variables are const declare them as such,

  • move non changing vars esp. arrays to PROGMEM (as crossroads said)

  • shorten texts for "debug" messages

  • if possible replace an array with a formula or function

  • if possible compress large arrays (e.g. RunLength, folding, mirroring etc

  • changing the algorithm used for the project might also have an impact on the variables needed.

  • ...

If you need a hand, post your code and we can give concrete advice for your case