How much free memory (RAM) left for app beside S110 stack?

[Martin]

I'm trying to make a simple BLE app based on LED button demo (BLE_LBS.C) that probably don't use much resources. I added FIFO UART communication routines and when I tried to allocate about 480B of global data for buffers I got RAM overflow error.

arm-none-eabi-ld.exe: region RAM overflowed with stack collect2.exe: error: ld returned 1 exit status make: *** [_build/ble_pokus_gcc_s110_xxaa.out] Error 1

This indicate there left only a few memory for application. Can you give me idea how much RAM does BLE stack take? A RAM layout diagram? Can I tune max. stack size?

This are the modules I link from my makefile: C_SOURCE_FILES += $(SDK_PATH)Source/sd_common/softdevice_handler.c C_SOURCE_FILES += $(SDK_PATH)Source/ble/ble_advdata.c C_SOURCE_FILES += $(SDK_PATH)Source/ble/ble_conn_params.c C_SOURCE_FILES += $(SDK_PATH)Source/ble/ble_debug_assert_handler.c C_SOURCE_FILES += $(SDK_PATH)Source/app_common/app_button.c C_SOURCE_FILES += $(SDK_PATH)Source/app_common/app_gpiote.c C_SOURCE_FILES += $(SDK_PATH)Source/app_common/app_scheduler.c C_SOURCE_FILES += $(SDK_PATH)Source/app_common/app_timer.c C_SOURCE_FILES += $(SDK_PATH)Source/app_common/app_fifo.c C_SOURCE_FILES += $(SDK_PATH)Source/app_common/app_uart_fifo.c

I also remember that I had to remove some debug module (maybe ble_debug_assert_handler.c) to be able to compile the example as it was. Maybe new SDK 5.1.0 takes more RAM than 4.x.x

[Ole Morten]

You can look at the Map file to know what consumes RAM in your application. In general, I'd also recommend you to search around a little on this site, to look at previous questions, for example this one.

The easiest way to save RAM is to reduce the heap size. When using gcc, you should also consider using newlib-nano, as mentioned here.

[Martin]

Thanks, 1st I tried to cut down heap by adding ASMFLAGS += -D__HEAP_SIZE=0x400 to Makefile, it worked

Then I tried use newlib-nano by adding LDFLAGS += --specs=nano.specs to Makefile, it worked even better!

Before: Memory usage: data=2280, bss=1632, heap=1024, stack=2048, free=1208 After: Memory usage: data=144, bss=1568, heap=1024, stack=2048, free=3408

Is there any drawback with using newlib-nano? I think it would be nice to have this GCC releated tricks in one getting started document inside SDK/DOC/ together with gcc makefiles for all examples :)

[Ole Morten]

Good that you got reductions! :-) As for the drawbacks, did you take a look at the links I posted here? https://devzone.nordicsemi.com/index.php/how-to-get-rid-of-impure_data#reply-4749 Especially this one should be useful: https://github.com/32bitmicro/newlib-nano-1.0/blob/master/newlib/README.nano

Improving gcc support is definitely something I want personally, which is why I'm maintaining this in my spare time: https://github.com/hlnd/nrf51-pure-gcc-setup Unfortunately, I can't promise any improvements for the official SDK...

[Martin]

I readed both documents about newlib-nano and I think that limitations (mostly on printf) will not limit me. I don't plan to use malloc (for printing to uart I use only vsnprintf) so maybe I could safely set heap to 0. I tried it and program run without change.

I already created Makefiles for BLE examples based on other makefile from standard example. Maybe someone else would use it so I attach them. That's a pitty you cannot have more influence on SDK, I think gcc on arm is very popular, both win32 and linux hosts...

gcc-makes.zip