Cannot add function in main.c

[10Hsin]

Hi, I would like to ask that, whenever I put my function in main.c, the borad become undiscoverable.

I'm using nRF51 with ble_app_uart_s110_pca10028, and below are my function and main

[RK]

what is the results of

ble_nus_string_send() .. 

which you put into err_code?

the next line, as is discussed here 50 times a week, is APP_ERROR_CHECK() which will go to the error handler if err_code is not zero. That's the most likely place you've ended up. Use the debugger to find out where you are and how you got there.

[10Hsin]

Sorry for asking a stupid question, but appreciate for your help!!