nRF52832 Circuit question

[jeonghun]

nRF52832 exposed part of datasheet exposed die pad What is wrong with not connecting GND to this part?

[ketiljo]

Connecting the center pad to ground is mandatory as it's to be considered as the main ground connection of the IC. 

[jeonghun]

What happens if I do not connect?

[ketiljo]

Mostly likely, the radio will be out of spec or may not even work.

[jeonghun]

Is there anything related to this 'NRF_FAULT_ID_SDK_ASSERT' error in that part?

[ketiljo]

Hard to say. There is some info in the ASSERT_INFO_T handler that will tell you why the assert happened. 

In any case, without grounding the center pad, anything can happen. If have a design that doesn't have a grounded center pad, you have to fix it.

[jeonghun]

I would like to know information ASSERT_INFO_T handler.

[ketiljo]

Please see the SDK documentation. It's probably easiest if you build the project with debug and logging enabled. The error code will show in the log output.