Arduino Memory

As I have been exploring the Arduino hardware platforms for my TBD project, I find myself forgetting the memory options available.  I'm recording here my findings so I can reference it later.

Arduino	Chip	Flash	SRAM	EEPROM
Nano 2.3	ATmega168	16K bytes	1024 bytes	512 bytes
Nano 3.0	ATmega328	32K bytes	2048 bytes	1024 bytes
Uno	ATmega328	32K bytes	2048 bytes	1024 bytes
Mega 2560	ATmega2560	256K bytes	8192 bytes	4096 bytes

SRAM (Static Random Access Memory) is where the sketch creates and manipulates variables when it runs.

EEPROM (Electrically Erasable Programmable Read-Only Memory) is memory space that programmers can use to store long-term information.

Flash memory is where the Arduino sketch is stored (program space).  The bootloader takes about 2 KB of flash memory and remaining space is for the sketch.

The Arduino IDE will tell you exactly how much Flash is being used after each compile/upload.  EEPROM is an older, more reliable technology. It is somewhat slower than Flash.  In Flash, a large block is erased all at once, much faster than the EEPROM method of going cell-by-cell.

If you don't need to modify the strings or data while your sketch is running, you can store them in Flash (program) memory instead of SRAM; to do this, use the PROGMEM keyword.

Part of my interest in the Arduino's memory is my concern about how much memory a sketch uses.  Here are some sites that provide insight and algorithms for calculating the memory:

• ATmega memory use
• Memory Areas and Using malloc()
• MemoryFree.c