"Undefined Reference" on the linker level

[Connie Violet]

Hi. I am a beginner with nrf52832. Trying to get Bluetooth and UART and a I2C peripheral working at the same time. I had a working version of the I2C peripheral and UART working together and tried to merge Bluetooth in, referencing the ble_app_uart example provided in nRF5_SDK_12.3.0. Currently when I try to do make flash I do not get any compiling errors, but I am getting linker errors that say that I have "undefined reference":

Linking target: _build/nrf52832_xxaa.out
_build/nrf52832_xxaa_twi.c.o: In function `twi_master_init':
/home/yilunsheng/src/accelerometer, SDK12.3, app_uart_merge/./twi.c:43: undefined reference to `nrf_drv_twi_init'
/home/yilunsheng/src/accelerometer, SDK12.3, app_uart_merge/./twi.c:46: undefined reference to `nrf_drv_twi_enable'
_build/nrf52832_xxaa_lis3dh.c.o: In function `lis3dh_read_data':
/home/yilunsheng/src/accelerometer, SDK12.3, app_uart_merge/./lis3dh.c:171: undefined reference to `nrf_drv_twi_tx'
/home/yilunsheng/src/accelerometer, SDK12.3, app_uart_merge/./lis3dh.c:180: undefined reference to `nrf_drv_twi_rx'
_build/nrf52832_xxaa_lis3dh.c.o: In function `lis3dh_init':
/home/yilunsheng/src/accelerometer, SDK12.3, app_uart_merge/./lis3dh.c:232: undefined reference to `nrf_drv_twi_tx'
collect2: error: ld returned 1 exit status
../nRF5_SDK_12.3.0/components/toolchain/gcc/Makefile.common:153: recipe for target '_build/nrf52832_xxaa.out' failed
make: *** [_build/nrf52832_xxaa.out] Error 1

Very confused about where the problem is.

[Jørgen Holmefjord]

I agree that dependencies could have been documented better, but this is more related to the modules themselves, rather than the sdk_config.h file. You still needs to include the source files of the dependent modules.

It might take some iterations to add all sub-modules that a module depends on, but the compiler will give you hints to what needs to be included/enabled.

[awneil]

Jørgen Holmefjord said:

this is more related to the modules themselves, rather than the sdk_config.h file

Indeed.

But see my linked thread - I didn't see anywhere that told me what files I needed to include!

Jørgen Holmefjord said:

the compiler will give you hints to what needs to be included/enabled

Indeed - but we're back to development by reverse-engineering again.

We shouldn't have to discover this stuff by trial & error - it should be clearly documented up-front.

[Jørgen Holmefjord]

Like I said, I agree that this is not well documented. We have an internal task requesting more documentation on library dependency documentation.

[awneil]

That's good to hear!

So, for input to that task, let's just look at the TWI driver as an example:

http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.2.0/group__nrfx__twi.html

I don't see anything there at all which tells which files need to be added to a Project.

There is a link to "TWI peripheral driver configuration"

This does list NRFX_TWI_ENABLED - and says  "set to 1 to activate"

But it's not really clear where that setting has to be made.

There's a note saying, "This is an NRF_CONFIG macro" - but what does that mean? 

I guess it's supposed to tell us that it's in sdk_config.h - is it?

It would be clearer if that were explicitly stated - with a link to the sdk_config.h documentation.

[Connie Violet]

Hi, Jorgen. I did checked and made sure that this part in my sdk_config.h look the same as what you pasted here but it did not solve the problem, and that was why I made this post.