ATMEL AVR1505 User Manual

http://www.BDTIC.com/ATMEL

AVR1505: XMEGA training - ADC

Prerequisites

• Required knowledge

Atmel® AVR® XMEGA™ - Basics Hands-On
Atmel XMEGA - EventSystem Hands-On (recommended)

• Software prerequisites

Atmel AVR Studio
WinAVR/GCC 20100110 or later

• Hardware prerequisites

Flat-headed isolated screwdriver
Xplain evaluation board
JTAGICE mkII

• Estimated completion time:

2 hours

®

4.18 SP2 or later

8-bit
Microcontrollers

Application Note

Rev. 8320A-AVR-08/10

1 Introduction

http://www.BDTIC.com/ATMEL

The ADC in the Atmel XMEGA A series has 12-bit resolution. It is capable of
converting up to 2 million samples per second (MSPS), and has a conversion time of
7 ADC clock cycles (add 1 cycle if gain is enabled) for 12-bit results. The input
selection is flexible, and both single-ended and differential measurements can be
done. The ADC can provide both signed and unsigned results, and an optional gain
stage is available to increase the dynamic range.

This training is based on the Atmel AVR Xplain evaluation kit which features the
ATxmega128A1 microcontroller. Different from most Atmel AVR ADCs, the ADC in
the XMEGA A has a pipelined architecture. This means that a new analog voltage
can be sampled each ADC clock cycle. Thus, a new ADC measurement can be
started while other ADC measurements are ongoing. The result is that the conversion
rate is much higher than the conversion time.

ADC measurements can either be done continuously, or be started by application
software or events from other peripherals in the device. Up to four different virtual
channels are provided. These have individual result and input selection (MUX)
registers to make it easier for the application to keep track of the data. It is also
possible to use DMA to move ADC results directly to memory or peripherals.

Figure 1-1. ADC Overview

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AVR1505

8320A-AVR-08/10

2 Overview

http://www.BDTIC.com/ATMEL

Here is a short overview of the tasks in this training:

Task 1: Single Ended Conversion

The most common use of the ADC feature is for single-ended conversions. Here you
will learn how this can be done with the Atmel XMEGA.

Task 2: Compare Function

The ADC has a compare function; this task shows how it works and why it is useful.

Task 3: Virtual Channels

This task shows a basic example on how virtual channels can simplify software and
ease the implementation when several ADC inputs are used in one application.

Task 4: Event Triggered Conversion

AVR1505

Events can be used to trigger one or several ADC conversions. It can also be used to
trigger two ADC’s at the same time for parts with dual ADC.

Good Luck!

8320A-AVR-08/10

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