Can not add twi function.

[agishii]

Hello I'm new of nRF seriese.

nRF51822CEAAD00(0x004d) SD130 ver2.0.1 kail Ver5.18 SDK11.0.0

I just finished the tutorial and now I'm making my new project with twi function. I had done with the tutorial of "our service" and it works well. Then, I made a project based on the "our service" project, and

1. add the "nrf_drv_twi.c" in the project,

2. add a line of "const nrf_drv_twi_t twi = NRF_DRV_TWI_INSTANCE(0);".

But I can not compile it. The error is like below. How should I do for using twi function?? The path is right, the c file exist, and I rebuild many times.

[agishii]