The scenario
An ATtiny85 controls a PT2258 I2C audio volume IC. Three pushbuttons provide volume up, volume down, and mute. Pull-up resistors and decoupling capacitors ensure reliable operation.
What is in this drawing
Read the decisions behind it.
01
Use I2C pull-ups on SDA/SCL for reliable PT2258 communication
02
Add 10k pull-ups on button lines with buttons to ground
03
Include AC sources and load resistors to avoid dangling audio nets
Reuse for digital preamps, active speakers, or any microcontroller-driven audio volume control using the PT2258 I2C interface.
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