NRF51 removing the HEAP

[ashelly]

I would like to remove the HEAP in my app to free up RAM.

• I removed all explict calls to malloc and family.
• I removed all variable length arrays, after finding that they generated calls to malloc.
• I set Heap_Size EQU 0; in arm_startup_nrf51.s

Are there any other steps to take? Any "gotcha's"? How do I ensure the compiler can't generate code that relies on a heap?

Do I need to change or remove the AREA HEAP ... section of the startup file?

[Andrew]

As long as there are no calls to malloc and all variables are explicitly defined you should be OK.

[ashelly]

what do you mean "explicitly defined"?

[Andrew]

Explicit as in, no variable length arrays. Basically, as long as nothing calls to malloc() or calloc(), you can zero out the heap size safely.

[Øyvind Karlsen]

Hi,

The simplest way of removing the HEAP is doing it in your compiler, for Keil this means using the MicroLIB functionality.

Go to Projects -> Options for Target

In the Target header check the tickbox for Use MicroLIB

More tips on reducing RAM usage can be found in this blog

Best regards,

Øyvind

[Elias]

For posterity:
If you're using C99, it turns out that using dynamically-sized arrays declared like "uint8_t my_array[input_size];" gets translated at compile-time to a malloc().