If they are larger objects containing structures and arrays these can chew up serious amounts of ram. These are variables which are declared but are no longer used. Sometimes, when you are in the heat of programming, you are trying so many things that stray variables get created. Remove Unused Variables and Check Your Types
Crashes arising from memory corruption are often unpredictable and difficult to reproduce.Īs a general rule, try to keep the RAM usage reported by the Arduino IDE to less than 60% of available RAM. If these dynamic variables fill up memory and start to overwrite the stack, then the program will crash. For example, what variable will come in and out of existence and when. The Arduino IDE helps by estimating the static ram required (variables etc) but it can’t know how the stack and heap will effect things. If you’re using dynamic memory, some RAM will be used by a heap too. You’re program needs some working space to keep track of function calls and local variables (this is called the stack). Its ok to use all of the flash memory available. Care needs to be taken to minimize its usage so you can maximize the functionality of your creation. The RAM available is usually significantly less than flash memory making it a precious resource for your Arduino project. And you can’t just pop in another stick of RAM or insert a USB memory stick. That’s not much, your laptop might have more than 4 billion bytes of RAM! So its pretty easy to run out on an Arduino.
It is volatile so each time the microcontroller is reset the RAM is cleared and repopulated. Dynamic things such as variables, structures, the stack etc all go into RAM. RAM, on the other hand, stores the data your program uses. An Arduino Uno has room for about 16,000 instructions. Flash memory is non-volatile, meaning it persists through a power cycle.
The instructions you typed into the Arduino IDE, translated to a language the micro can understand. Microcontrollers have multiple forms of memory but the two main ones are Flash and RAM.įlash stores your program. To make matters worse these resets occur at strange places often sending you down a rabbit hole, looking for bugs that never existed in the first place. What happens when an Arduino or other microcontroller runs out of random access memory (RAM)? Typically the Arduino goes crazy and resets itself in strange places.