January 3, 2017

A reset button

Anyone who has an Orange Pi will tell you that there are two things it needs badly. Namely, a power LED and a reset button. Both are more or less trivial, but it is all about details.

Ignoring the power LED for now, I have added a reset button to my Orange Pi PC. Actually what I did was to add a two pin header and carefully wired it to the appropriate points on the PCB. This allows me to connect the button of my choice, or as I did initially to just short across the header with a screwdriver or other handy tool. A button is far better and worth the trouble.

There are questions about this (rather poorly handled if I do say so) on the various forums. I will get busy and add photos; someday I hope. But in the meanwhile here is some useful information.

The schematic shows a "reset option". This is misleading. It is not an option, it is a necessary circuit and is present on every Orange Pi PC or PC plus. You can look at the circuit and after some study understand how it works. What you need to do is to wire a switch across the capacitor that stands above the diode in the circuit. Short out that capacitor and you get a reset.

For whatever reason the reset circuit is surprisingly complex. The usual circuit is just a resistor and a capacitor, but here we have a transistor inverter feeding the reset. The capacitor is not connected to ground, so neither point on the connector you add will be either. Find the schematic and look it over.

The recipe

Set the board in front of you with the HDMI connector towards you. This will place the ethernet and USB connectors facing to your right. The components of interest are to the right of the HDMI connector between the microphone and the audio jack.

Identify a diode along the card edge closest to you. (This is the only component along the card edge to the right of the microphone). This has a band on the left side. The left side of this diode is one point. The other component to identify is a capacitor above the diode. This is a tan surface mount component. It is immediately above the right side of the diode on the PC Plus. On the PC, there is a small resistor between the diode and this capacitor. In either case, you want to solder onto the right side of this capacitor.

If you care to, you can use a meter to verify that the left side of this capacitor is connected to the left side of the diode already mentioned.

Connect a momentary switch (button) across these two points and Fred is your uncle!

Have any comments? Questions? Drop me a line!

Tom's electronics pages / tom@mmto.org