ble_app_uart example some uart issue on fanstel EV-840 DK

Hi there,

I am using WIN10, Segger studio 4.52c and nRF SDK16. 

I can successfully run ble_app_uart example on PCA10056, but when i try to run same code on fanstel EV-840 dev board, application crashes after uart_init() function, actually APP_UART_COMMUNICATION_ERROR event is received in event handler. (if i comment uart_init() function everything else works fine.. i can connect with phone and all...)

Then i tried Uart example in  examples\peripheral\uart and i got the same behavior as in ble_app_uart.

But when i tried serial_uartes example in examples\peripheral\serial_uartes strangely enough this worked perfectly and i can send data on both the uarts.

So there is no hardware issue in UART for sure and i am using RX on 26 and TX on 27 on EV_840.

Now i am out of options to try out, please suggest what can be wrong and why i can't run ble_app_uart example on fanstel EV-840. 

I am sure i am missing something very basic.

Thanks, Rishi