Custom Board - can't use more than 4 buttons

Question

We did initial work on the NRF51DK (PCA_10028).
We are using SDK 12 and ARM-GCC.
We were able to compile and run successfully the experimental_ble_app_blinky and connect using your android App - nRF Blinky.
We developed a custom board and were able to successfully run and connect to that with the experimental_ble_app_blinky.
Our custom board has 6 buttons. I changed the C-FLAG to our custom board in the MAKEFILE and that seems to be working fine.
If I add the other 2 buttons in the program, the program compiles fine (no errors) but will not broadcast BLE or have any other functionality. If I comment out any of 2 of the buttons in the static app_button_cfg statement, it works again. Here is the line below where it will work - if I take the comments out, it does not work. 
 static void buttons_init(void){
uint32_t err_code;

//The array must be static because a pointer to it will be saved in the button handler module.
static app_button_cfg_t buttons[] =
{
 {B1, false, BUTTON_PULL, button_event_handler},
 {B2, false, BUTTON_PULL, button_event_handler},
 {B3, false, BUTTON_PULL, button_event_handler},
 {B4, false, BUTTON_PULL, button_event_handler}
 //{B5, false, BUTTON_PULL, button_event_handler},
 //{B6, false, BUTTON_PULL, button_event_handler}
 
};

err_code = app_button_init(buttons, sizeof(buttons) / sizeof(buttons[0]),
 BUTTON_DETECTION_DELAY);
APP_ERROR_CHECK(err_code);}
 
 I defined the button's pins with - "#define B1 21" as an example. The button pins are 21,22,23,24,25,28. 
 What am I doing wrong? Is there something that I am not setting properly in another header file?
I can make any 4 buttons work so I know the I/Os are good - I just can't make all 6 work.
Any help would be appreciated.

Sigurd · Accepted Answer

With a custom board you will need to modify the board files.
You can find the board files under: 
 \SDK_INSTALL_FOLDER\examples\bsp
 
 When creating a new board file, simply copy the pca10028.h file, rename it, and modify it after your requirements. Then you have to modify boards.h to support your new file, and add a new define that you can specify in the makefile to include your modified file. 
 A button press is a low power event, so you will also need to increase GPIOTE_CONFIG_NUM_OF_LOW_POWER_EVENTS which can be found in sdk_config.h.

Custom Board - can't use more than 4 buttons

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