Electronics Introduction

  This is a fundamental and important concept when starting with STM32 (or any microcontroller ). Here’s a clear breakdown of what these pins mean and how to handle them on an STM32. The Quick Answer (TL;DR) VDD:   Positive supply voltage  for the  digital  internal logic. (e.g., 3.3V) VCC:   Positive supply voltage  for the  analog  peripherals (ADCs, DACs, etc.) and I/O pins. Often connected to the same 3.3V rail as VDD. VSS:   Ground reference  for the digital circuitry (0V). VSSA:   Ground reference  for the analog circuitry. (Must be connected to VSS but with a careful layout). VREF+ / VREF-:   Reference voltage  for the Analog-to-Digital Converter (ADC). Provides a cleaner reference than VCC/VSSA for accurate measurements. VBAT:  Backup power input for the Real-Time Clock (RTC), backup registers, and sometimes the low-power oscillator when main power is off. VEE:   Negative supply voltage . Rar...