This is a convenient way to break out the SPI device on a Raspberry Pi. The 2x3 header has the same pinout as the AVR ISP, with the !RESET line replaced with !CS. In fact, you probably could use this to perform AVR ISP programming at 3.3v.

The SOT23-3 is an AP2331 that protects the Pi’s 3.3v bus from short circuit and hot-plug transients. The two caps are 0.1µF.

This little board will adapt a Bus Pirate v4 for programming SPI flash chips. The 6 pin pinout is the same as the AVR ISP pinout, with !CS substituted for !RESET. If you add that connector to your board to facilitate flash programming in situ, then all you have to do is do whatever is necessary to keep the SPI bus quiescent (usually just holding the controller in RESET will work), then program away.

This is a boost converter powered LED board. It’s intended to be populated with 21 SM0603UV-405 UV LEDs, but really any 0603 LED would work just fine. The boost converter is the AP3015. The two 1210 caps are 10 µF, the inductor is 10 µH and the diode is an MBRA340 Schottky diode. The resistor divider values of 51.1kΩ and 3kΩ yield an output voltage of 22.14 volts, or 3.16 volts across each LED (there are 3 parallel strings of 7 LEDs in series). It’s recommended that the input power be 9 VDC.

The “S” in SAO now stands for Serial.

This SAO will connect two badges together in a null modem arrangement, wiring one badge’s TX to the other’s RX and vice versa.

Put two shrouded 2x3 connectors on the bottom of the board. Put a 1x2 connector on the top and short it (or not) with a shorting jumper depending on whether you want to share power between the two badges or not.