Connecting UART Data to development board PCA10040

I am trying to transfer data from a USB to serial converter board (called board A) to the nrf5 board (called board B). I made the connection over a bread board, the transmitter from board A  is connected to pin 06 on board B, it is also at the same time connected to the receive in Board A. I am sending zeros and receiving zeros at board A. I want to see these zeros at board B.

The baud rate on both is adjusted to 19200. The ground is connected on both boards.

I started uart_pca10040 example but I don't get any data received on board B. I tried to connect pin 5 with 7 for CTS and DTR but also I don't see any data.

The data voltage on Board B is 2.1 V.