No idea what your Pine is doing? Serial console!

[hyperlogos]

Short, short form:

• Connect the GND wire to Pin 6 or 9 of the EXP connector.
  
• Connect the RX wire to Pin 7 of the EXP connector.
  
• Connect the TX wire to Pin 8 of the EXP connector.
  
• Connect to the COM port at 115,200 bps.
  

I used a CH340G USB to serial which I bought for talking to ESP-01 ESP8266 boards. You can use basically any USB to TTL Serial. I used PuTTY to talk to the serial, which Windows helpfully told me was COM13 when I connected it. Since my USB to serial has a female header, I used three male-to-female jumper wires to connect it to the EXP header. Pins 7, 8 and 9 are right next to the memory card slot. I used pin 9 as ground.

When I plugged in the power connector, I got to see the full boot process, including formatting of the memory card.

I got the information here: http://elinux.org/Pine64#Serial_Console

In the case of the latest (20160303) Android release, there is a root shell attached to this port. If you have no video, you can execute a safe shutdown here with "reboot -p". I have not tried Linux yet, but I would anticipate a normal login prompt there after boot.