While 32- and 64-bit microcontrollers (MCUs) get most of the attention these days, the humble 8-bit MCU is still a very important part of the design world, and the storied AVR is one of the most well-known 8-bit architectures. At Embedded World 2024, Microchip demonstrated its continuing commitment to the AVR line by announcing the new AVR DU MCU family.
Microchip’s new AVR DU chip is an important addition to its USB MCU portfolio, offering enhanced code protection and up to 15 W of power delivery. Image used courtesy of Microchip
The new chip family builds on the AVR legacy and brings new USB and security capabilities.
Bringing More USB Functionality to the 8-bit World
According to Microchip, anyone familiar with AVR development can easily transition to the AVR DU chip. With the MCU’s advanced USB features, 8-bit device developers can quickly add USB connectivity and charging without increasing the parts count. While some existing AVR chips do have built-in USB connectivity, the most popular models do not. The new DU family also includes charging management, unlike earlier USB-AVR MCUs.
All About Circuits’ Jeff Child discusses new AVR offerings with Microchip’s Odd Jostien Svendsli at Embedded World 2024.
Its USB data interface is a full-speed USB-2.0 interface (12 Mbps) using the standard D+ and D- data pins compatible with any USB connector. In addition to USB 2.0 data, the AVR DU MCUs are compatible with USB-C 15-W mode. This compatibility enables on-chip management of charging current up to 3 A at 5 V. With the DU’s built-in USB data and power, what was likely a two-chip solution before is now a one-chip, reduced-passives solution.
AVR DU Microcontroller Architecture
The DU family (datasheet linked) contains parts with 14 to 32 pins, 16 to 64 KB of Flash, 2 to 8 KB of SRAM, and 256 B EEPROM. It is compatible with supply voltages from 1.8 V to 5.5 V. Microchip based the family on the popular AVR CPU at 24 MHz.
The AVR CPU is a Harvard architecture (independent code and data memory spaces) RISC microcontroller popularized by open-source Arduino boards. It has an efficient single-level pipeline design, with most instructions taking just one or two clock cycles. It includes a diverse set of analog and digital peripherals, including four programmable lookup tables (LUTs) to further reduce external parts count when the application requires a small amount of digital logic.
AVR DU block diagram. Image used courtesy of Microchip
The new MCU family targets small devices where processing needs are within the 8-bit’s capabilities and space is at a premium. The chip would be a useful host MCU for a wide range of embedded systems, including wearables, home appliances, and industrial applications. The 15-W charging capability means the part could be used in power bricks or other power-hungry rechargeable devices that need to keep cost and parts count low. The MCU offers 5-V support, aiding in its compatibility with legacy systems.
MCU Security Features
Even 8-bit MCU applications require security, and this new AVR has features to address this need. Bad actors can reprogram 8-bit MCUs through the in-field upgrade capability. Microchip’s Program and Debug Interface Disable (PDID) feature can be set to lock out the programming and debugging interface to prevent false upgrades or debug vector attacks. Additionally, the MCU family uses Read-While-Write (RWW) Flash to allow secure bootloaders to safely fix bugs and update code.
Development Tools and Packaging
Microchip has released a development board along with the AVR DU family to help coders to get started right away. The board comes in Microchip’s Curiosity Nano Development Board form factor. The Curiosity Nano environment is a common platform for development boards supporting a wide array of Microchip PIC and AVR processors.
AVR DU family development board. Image used courtesy of Microchip
The chip uses the AVR languages and development tools and is fully supported by the MPLAB X IDE and MPLAB XC8 C compiler. The MCC Melody tool allows designers to easily configure the USB software stack.
Microchip offers the MCUs in both through-hole and surface mount packages—the largest being a 28-pin SPDIP at 300 mils wide with 0.1” pin spacing. The smallest comes in a 20-pin 3 mm x 3 mm, 0.4mm pitch VQFN package. This range of offerings gives the family use in hand-wired breadboards, extremely space-constrained devices, and anything in between.
