Should I do something before opening CON2~CON4 of mini6410?

I had got a mini6410 for 4Mbps UART. However, I could not use it due to no signal in CON2~CON4. I had checked the voltage of them. It's odd. The voltage of TX/RX of CON3 and CON4 are 0V. The voltage of CON2 TX is 3.26V and The voltage of CON2 RX is 0V. The voltage of TX/TX of CON1 are correct, 3.26V. Anything I missed to enable CON2~CON4? I had checked it under Android and Linux using the official images. The results are the same on them. Thanks.