CSR1000 allocate memory

Question

I'm currently playing around with the CSR 1000 chip and I wanted to allocate memory. I tried using malloc but the compiler tells me:

undefined reference to `malloc'

I assume that is because gcc is run with -nostdlib parameter

So please could somebody with CSR uEnergy SDK experience, tell me why I can't allocate memory, and how I should do it instead??

Answer 1

If there is an SDK bundled with that chip that provides basic routines for memory allocation then use those, alternatively you can write your own allocator or use an existing one off of the web (with some fiddling).

As a quick solution you can probably mark a region in memory using a modified linker script or by using the gcc 'section' attribute (more here) and then use that as your heap arena in your malloc allocator.

A very simple allocator would not keep any accounting information such as headers/footers but rather allocate linearly one region after another (free-ing would essentially be a no-op in this case), this won't get you far but you will be able to run simple programs.

You probably want something more sophisticated, you could also look into implementing some kind of memory pool or any of the standard allocation algorithms.

The classic book The C Programming Language by Dennis Ritchie and Brian Kernighan provides a simple memory allocator if I re-call correctly. You may want to have a look at that.

Answer 2

I have three months of experience with this chip.

The malloc function is found in standard C library, which is typically available in desktop software development or embedded linux. But this is a small and resource-limited embedded chip. There is no standard C library.

If you browse the uEnergy SDK installation directory, something like this: C:\uEnergy_SDK-2.0.0\doc\reference\html\index.html. Click Modules tag on the top. You will find that under the section "C Standard Library APIs", CSR provides a few functions that mimic a subset of the standard C library. Unfortunately, there is no methods like malloc.

In general, when you work with small embedded systems, it is quite often that there is no dynamic memory allocation. However, for RF applications which are usually event-driven, there is typically a simple dynamic memory allocation function provided so incoming packets can be handed to you by the OS to your application. I used TI's CC2430 and its Zigbee stacks. They provide functions osal_mem_alloc and osal_mem_free, which mimic the malloc and free in the standard C library.

From my experience working with both chips, I found that CSR is much more protective than TI, in the same way as iOS vs. Android. You don't know what MCU they use except they tell you that it is a 16-bit RISC.

I suspect they have the dynamic memory allocation internally but your application just can't use those functions. RF packets are handed to you by the OS in the AppProcessLmEvent function, from there you get your data via the p_event_data pointer. You don't have to deallocate it as the OS will do it for you once you finish handling that event.

So back to your question, you can allocate memory so you just reserve a block of memory as global array and work on it.

Hope this helps.

Answer 3

add #include <malloc.h> to the head of your file