wiring

OK, so the wiring is quite simple.

5 volts DC power supply and HDMI cable are "permanently" wired into the back of the unit.  The HDMI cable simply plugs directly into the Pi (regular HDMI for RPi3B, the OPiZero2 needed micro-HDMI).  There is a wooden cable-clamp to relieve any strain on the Pi from outside forces on the cable.  The 5 volts line runs to my home-made circuit board, which is connected to the switches and LEDs of the front panel, and also runs to the Pi.

The three buttons (back-arrow, play, forward-arrow) are cute-looking wooden actuators which push three roller microswitches.  These each connect a given Pi I/O line to ground, versus three 2.2k resistors pulling up to 3.3v (which is an adequate logic H even for 5v systems).  I've used the same physical pin numbers on the Raspberry Pi as I used with the Orange Pi, even though the connectors are not identical in naming or even size (the RPi one is the longer extended type with 40 pins).

The switch hardware also pulls 3.3v and ground from the connector (wires simply soldered to the back of the pins, where it won't interfere with still attaching a connector -- although I don't plan this).  And I use such soldered connections to the 40-pin connector, to attach the input 5v and gnd to run the power to the unit, rather than using the micro USB plug (or USB-C, for the Orange Pi) that they suggest.

I also run the 5v to supply a number of LEDs, through 2.2k resistors.  These are red and blue backlight LEDs, which shine through the edges of my wooden buttons, creating a purple gradient (I'll have to show a photo, presumably coming soon).  This is just for visibility in the dark, the lights don't change when the buttons are clicked or any such.


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