June 8, 2018

A reset button for the NanoPi Neo

Like the Orange Pi boards, this board also lacks a reset button. As a developer writing bare metal software, I am needing to reset the processor on a regular basis. This can be done by pulling power, or so you would think, but I find that if a USB to serial console is attached, I have to disconnect it also before I get a reset. A bonafide reset button is a huge benefit, and not too hard to wire up.

The circuit on the NanoPi is simpler than the Orange Pi. On the NanoPi, we have the usual capacitor to ground being fed by a resistor, so we just need to find that capacitor-resistor junction, connect a wire and then switch that to ground to get a reset.

The capacitor and resistor are C40 and R5 and are on the bottom of the PCB. Use a meter to find out which end of C40 goes to ground and which end connects to R5, then solder a wire to the end which is connected to R5. Another wire needs to be soldered to ground, but that is available in many more convenient locations.

I epoxied a 2 pin header to the back of the ethernet jack. I used some wire wrap wire (nice thin solid wire) and ran it through one of the holes for the audio connector. I attached to ground at one of the places the USB connector metal shroud is soldered to the PCB.

This requires some careful soldering (I worked under a low power microscope). In particular, work quickly when soldering to C40 to avoid damage.

Have any comments? Questions? Drop me a line!

Tom's electronics pages / tom@mmto.org