This is just a simple experiment.
Basically, I wanted to manage 8 different LEDs with an ATTiny and for this I need a shift register. I also want to connect a 9 volt battery to the project so a 5V voltage regulator is needed. Furthermore, 8 leds and 8 resistors are needed. Plus a simple script to switch each individual LED on or off.
I use three pins of the ATTiny to manage the leds, which are the three analog out pins. PB0 and PB1 are not used but they are redirected to the bottom of the board.
PB2 connects to the data pin for the switch register. PB3 connects to the Clock pin and PB4 connects to the Latch pin. The 8 output pins connect to the LEDs from right to left, with the most significant bit being the left one. (The one closest to the power source.)
The four openings are ground, VCC, PB0 and PB1. These can be used to connect to sensors or for other purposes but basically, it provides two analog input pins for whatever project that is created around it.
The example code is just to show the LEDS will work correctly. But if you add one or two sensors then it should not be too difficult to have the LEDS represent the value of the incoming signals.