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Microchip AVR128DB48 - A Signal Conditioning Player

If you’re an avid AVR user, you are probably already well aware of the Microchip AVR128DB48 microcontroller. For those of you who may be new to AVR devices, we will be giving you an overview of the DB family in this article and how they differ from their sister devices in the DA series.

AVR devices

Both series share a great deal in common, so let’s start with the similarities by beginning with part numbering, which is actually pretty sensible as conventions go: each device is named AVRfffDApp or AVRfffDBpp, where fff is the flash size (in KB), and pp is the number of pins. Currently, there are 32 KB, 64 KB, and 128 KB Flash variants that come in 28-pin to 64-pin package options.

The same AVR core is common to both series:

AVR Core

The CPU runs at up to 24 MHz off a high-precision internal oscillator with selectable frequency and features niceties like single-cycle I/O register access and a two-level interrupt controller.  

One feature set essential to flexible low-power operation is the 3 sleep modes, which include:

  1. Idle with all peripherals running for immediate wake-up.
  2. 2. Standby with configurable operation of selected peripherals and SleepWalking peripherals.
  3. 3. Power-Down with full data retention.

Both series run over the full supply voltage range of 1.8V to 5.5V and are available for extended temperature (-40°C to 125°C) operation.

The place where we start to see some differences is in the peripherals. Most peripherals are common to both families, but where the DA series leans more towards control applications (and comes equipped with a peripheral touch controller for capacitive touch applications), the DB series is set up with some useful signal conditioning hardware.

AVR peripherals

Analog Signal Conditioning

The analog signal conditioning is based around a combination of 3 Operational Amplifiers. Each of these peripherals is individually configurable in pretty much any way you might want to configure a discrete component.

Op Amp Diagram

They can be used as stand-alone devices simply using selectable I/O pins for external connections. Alternatively, designers can use the internal resistor ladders for each Op Amp to create a programmable gain amplifier.

Op Amp Configurations

Want differential inputs? Two Op Amps can be combined to form a differential amplifier that can then be used with the 12-bit differential ADC peripheral on the AVR device. When you need extremely high impedance inputs, for use with something like a low-level output transducer in a noisy environment, you can configure all 3 Op Amps together as an instrumentation amplifier.

To help you get the most out of these peripherals, there is a full toolchain that takes you from circuit simulation through to signal visualisation.

MPLAB - MINDI, Configurator and Dave Visulizer

MPLAB MINDI contains the Op-Amp SPICE model for the AVR DB parts, so you can visually create your circuit and simulate it. MPLAB CODE and MPLAB START are two graphical code generation tools that both support AVR DB parts making it easy to see which I/O pins are being used and which peripheral is connected to what other part. When your code is running, MPLAB DATA VISUALIZER can show you what your output signals will look like.

Multi-Voltage I/O (MVIO)

Another really nice feature included on the DB part is multi-voltage I/O. Usually, when an MCU is connected to a sensor or other device running off a different supply voltage level, designers find themselves taking up valuable board space with level shifters to get everything to play nice together.

MVIO

MVIO means that two different supply voltages can be used by two different I/O ports on AVR DB devices. Both voltages can range from 1.8V to 5.5V and peripherals that would normally use a port, like I2C or PWM, can use the ports as normal, making everyone’s life so much simpler.

The AVR DA /DB families are a fun and low-cost entry into 8-bit application development but despite their low cost, the AVR DA/DB families are both serious devices, with functional safety qualifications for both industrial and automotive safety-critical applications.

Going Forward

If we have piqued your interest and you want to find out more about this great little 8-bit microcontroller, here is a link for the datasheet.

You can also try it out using the low-cost Microchip AVR128DB48 Curiosity Nano Evaluation Kit (209-7644) which we will be demonstrating in the video.

Video

In this video, I try out the AVR128DB48 eval board with a couple of examples that allow me to get to grips with Microchip's MPLAB development environment.

The kit used in the video includes:

AVR128DB48 Curiosity Nano Evaluation Kit (209-7644)

AC164162 for Mikrobus Click Modules (193-6490)

MIKROE-3325 POT 2 Click (185-2178)

Mark completed his Electronic Engineering degree in 1991 and worked in real-time digital signal processing applications engineering for a number of years, before moving into technical marketing.
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