Using NuttX as a library

It is possible to use NuttX as library, then you don’t need to compile the source code all the time, just modify your application and link it against the NuttX library.

Here I will explain step-by-step how to do that.

I will consider that you just entered on nuttx/tools and executed the ./configure.sh to select your board and your application profile (here my application is called “hello” and CONFIG_USER_ENTRYPOINT=”hello_main”). Then now instead of executing “make” to compile the source code you should to execute:

make export

If everything worked as expected you will get the file “nuttx-export.zip”. Extract this file and create your application inside it. Here I create a hello.c file with it:

#include 

int hello_main(void)
{
        printf("Hello World!\n");
        return 0;
}

Now I compiled it this way:

$ arm-none-eabi-gcc -c -fno-builtin -Wall -Wstrict-prototypes -Wshadow -Wundef -g -mcpu=cortex-m4 -mthumb -mfloat-abi=soft -I. -isystem ./include   -pipe -I "./include"  hello.c -o  hello.o

We just need to link again libnuttx.a to generate our nuttx ELF:

$ arm-none-eabi-ld --entry=__start -nostartfiles -nodefaultlibs -T./build/spificonfig.ld -L./libs hello.o -o nuttx.elf --start-group -lnuttx "/usr/lib/gcc/arm-none-eabi/6.2.1/thumb/v7e-m/libgcc.a" --end-group

And to generate the finaly binary from the ELF:

$ arm-none-eabi-objcopy -S -O binary nuttx.elf nuttx.bin

It is also a good idea to generate the map of symbols with the physical address of each function:

$ arm-none-eabi-nm nuttx.elf | \
grep -v '\(compiled\)\|\(\.o$\)\|\( [aUw] \)\|\(\.\.ng$\)\|\(LASH[RL]DI\)' | \
sort > System.map

Well done, now just flash it using OpenOCD and STLink-V2 :

$ sudo openocd -f interface/stlink-v2.cfg -f target/lpc4330.cfg -c init -c "reset halt" -c "flash write_image erase nuttx.bin 0x14000000"
Open On-Chip Debugger 0.10.0 (2017-02-12-09:48)
Licensed under GNU GPL v2
For bug reports, read
	http://openocd.org/doc/doxygen/bugs.html
Info : auto-selecting first available session transport "hla_swd". To override use 'transport select '.
adapter speed: 500 kHz
Info : The selected transport took over low-level target control. The results might differ compared to plain JTAG/SWD
Info : Unable to match requested speed 500 kHz, using 480 kHz
Info : Unable to match requested speed 500 kHz, using 480 kHz
Info : clock speed 480 kHz
Info : STLINK v2 JTAG v17 API v2 SWIM v4 VID 0x0483 PID 0x3748
Info : using stlink api v2
Info : Target voltage: 3.273164
Info : lpc4350.m4: hardware has 6 breakpoints, 4 watchpoints
target halted due to debug-request, current mode: Thread 
xPSR: 0x01000000 pc: 0x10402c40 msp: 0x10087ff0
auto erase enabled
Info : Found flash device 'win w25q64cv' (ID 0x001740ef)
Warn : no flash bank found for address 28000000
Warn : no flash bank found for address 280074c4
wrote 0 bytes from file nuttx.bin in 0.087209s (0.000 KiB/s)
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