ADC (Analog to Digital Converter)

The ADC (Analog-to-Digital Converter) in the ATMEGA328 is used to convert analog signals (voltages) into digital data that can be processed by the microcontroller. The ADC is typically used in applications where the input signal is an analog value, such as reading sensors, measuring voltages, etc. The ATMEGA328 features a 10-bit ADC, which provides a resolution of 1024 distinct values for any input voltage between 0 and the reference voltage.

The ADC on the ATMEGA328 is capable of reading multiple channels (pins) and can be configured for various reference voltages. It is essential to understand the registers controlling the ADC and how to utilize them to get accurate readings.

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🔗 Resources

Here you'll find a collection of useful links and videos related to the topic of AVR microcontrollers.

ADC Overview

ADC Overview
├── Documentation
│   ├─ [ADC Channels]
│   │   ├─ Inputs — ADC0 to ADC7
│   │   ├─ Multiplexer — ADMUX (MUX bits)
│   │   └─ Differential channels & gain
│   │
│   ├─ [ADC Voltage Reference]
│   │   ├─ Registers — ADMUX (REFS bits)
│   │   ├─ Options — AREF pin, AVcc, Internal 1.1V reference
│   │   └─ Considerations — Noise, stability
│   │
│   ├─ [ADC Prescaler]
│   │   ├─ Registers — ADCSRA (ADPS bits)
│   │   ├─ Division factors — 2, 4, 8, 16, 32, 64, 128
│   │   └─ Impact — Sampling rate and accuracy
│   │
│   ├─ [ADC Triggering]
│   │   ├─ Registers — ADCSRA (ADATE), ADCSRB
│   │   ├─ Modes — Free-running, Timer Compare Match, External Interrupt
│   │   └─ Use cases — Periodic sampling
│   │
│   ├─ [ADC Interrupts]
│   │   ├─ Registers — ADCSRA (ADIE), ADIF
│   │   ├─ Operation — ISR trigger when conversion complete
│   │   └─ Clearing flags — Write 1 to ADIF
│   │
│   └─ [ADC Conversion Calculation]
│       └─ Topics — Voltage to ADC Value, ADC Value to Voltage
│
├── [API_Reference]
│    ├─ File — adc.h / adc.c
│    ├─ Functions — Init, internalTemp, Read
│    └─ Purpose — High-level ADC peripheral interface for reading analog inputs and internal temperature sensor
|
└── Registers
    ├─ [ADMUX]   — ADC Multiplexer Selection Register — Channel & reference selection
    ├─ [ADCSRA]  — ADC Control and Status Register A — Enable, start, prescaler, interrupt
    ├─ [ADCSRB]  — ADC Control and Status Register B — Auto trigger sources
    ├─ [ADCL]    — ADC Data Register Low byte
    ├─ [ADCH]    — ADC Data Register High byte
    └─ [DIDR0]   — Digital Input Disable Register 0 — Disable digital buffers on ADC pins

Tip

The resources are detailed in the sections below.
To access any of them, simply click on the corresponding blue link.

• ADC Channels

  Describes all ADC input channels, multiplexer usage, and differential measurement options.

• ADC Voltage Reference

  Details the available voltage reference sources (AREF, AVcc, Internal 1.1V) and their trade-offs.

• ADC Prescaler

  Explains how to set the ADC clock using prescaler bits in ADCSRA for optimal accuracy.

• ADC Triggering

  Shows how to use free-running and auto-triggered ADC conversions.

• ADC Interrupts

  Describes enabling ADC interrupts and writing ISRs for conversion completion.

• ADC Conversion

  This section explains how to convert between analog voltages and digital ADC values using the ATmega328's 10-bit ADC. It covers two key operations:

  • Voltage to ADC Value:
    Learn how the ADC translates an input voltage into a 10-bit digital value (0–1023), based on the reference voltage.
  • ADC Value to Voltage:
    Understand how to convert the digital ADC result back into the corresponding analog voltage using a simple formula.

• API Reference

  This section provides detailed descriptions of the functions in the adc.h and adc.c files for handling ADC operations on the ATmega328 microcontroller. Each function is designed to manage analog-to-digital conversions, read data from specific ADC channels, and interact with the internal temperature sensor. These APIs simplify ADC initialization and data acquisition, making it easier to implement analog input handling in your projects.

• AVR Microntroller

  This repository contains comprehensive resources for AVR microcontrollers, including hardware schematics, software libraries, and educational projects.

Videos Overview

AVR, Analog
  └── [aKaReZa 77 - AVR, Analog - ADC]
       ├─ ADC Basics — Block diagram, control & data registers.
       ├─ Functions — Configuration + raw value reading.
       ├─ Voltage — Measurement via ADC.
       ├─ Channels — Multi-channel measurement.
       ├─ Temperature — External + internal sensor usage.
       └─ Accuracy — Noise canceller feature explained.

aKaReZa 77 – AVR, Analog - ADC Learn about the features of the Analog-to-Digital Converter (ADC) in AVR microcontrollers, including block diagrams, control and data registers, voltage measurement, multi-channel measurement, analog temperature sensor connection, internal temperature sensor usage, and noise canceler capabilities.

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