Tag Archives: Frédéric Gaillard

An MCU or MPU, that is the question: Part 1

Selecting the most appropriate device (an MCU or MPU) for a new project or design can be somewhat daunting. Indeed, engineers typically analyze a wide range of variables, including price, performance and power consumption.

To make the process easier, we will examine some of the primary differences between an MCU (microcontroller) and MPU (microprocessor).

“Typically, an MCU uses on-chip embedded Flash memory in which to store and execute its program,” Frédéric Gaillard, product marketing manager and Andreas Eieland, senior product marketing manager, told Bits & Pieces.

“Storing the program in this way means that the MCU has a very short start-up period and can be executing code very quickly. The only practical limitation to using embedded memory is that the total available memory space is finite. Indeed, most Flash MCU devices available on the market have a maximum of two Mbytes of program memory and, depending on the application, this could prove to be a limiting factor.”

In contrast, MPUs are not limited by memory constraints in quite the same way, as they employ external memory to provide program and data storage. The program – typically stored in non-volatile memory such as NAND or serial Flash – and is loaded into an external DRAM at start-up and subsequently commences execution. On a practical level, this means the MPU will not be up and running as quickly as an MCU, although the amount of DRAM and NVM engineers can connect to the processor is in the range of hundreds of Mbytes and even Gbytes for NAND.

Another notable difference between MPUs and MCUs is power consumption methodology. By embedding its own power supply, an MCU is fine with just one single voltage power rail. However, an MPU typically requires several different voltage rails, prompting the use of additional on-board power ICs/converters. And while MPUs do have low power modes there are not as many or as low as the ones you would find on a typical MCU.

“With the external hardware supporting an MPU has an added factor, putting an MPU into a low power mode might also be slightly more complex,” the two explained. “In addition, the actual consumption of an MCU is magnitudes lower than an MPU, in low power mode for example with SRAM and register retention, you can consider a factor 10 to 100. Obviously this is directly related to the amount of RAM an operating system requires and therefore to be powered to resume operation instantaneously.”

Clearly, design specs are critical when it comes time for an engineer to select an appropriate device for a specific application. For example, is the number of MCU peripheral interface channels sufficient? Do marketing specifications stipulate a user interface (UI) capability that is simply impossible with an MCU due to a lack of on-chip memory and performance?

“When embarking on the first design engineers know it is highly likely there will be many product variations,” said Gaillard and Eieland. “As such, it is very possible a platform-based design approach will be preferred. This would stipulate more ‘headroom’ in terms of processing power and interface capabilities in order to accommodate future feature upgrades.”

Want to learn more about the differences between MPUs and MCUs? Stay tuned to Bits & Pieces for part 2 of “An MCU or MPU, that is the question.”

Designing next-gen UIs with the SAMA5D3 MPU

Intuitive user interfaces (UIs) are ubiquitous for smartphones, tablets and personal media players. But what about user interfaces in the world of industrial automation applications and home control units?


Frédéric Gaillard, Atmel Product Marketing Manager, tells Bits & Pieces the use of MIMIC diagrams and traditional switches and rotary controls are still quite commonplace for industrial equipment. Ditto for home thermostats, the majority of which are mechanical.

“There are actually some very good reasons for this, as gloved hands, moisture, and condensation can play havoc with touchscreen controls. The industrial operating environment may dictate large switches for these reasons,” Gaillard explains.

“Safety considerations may warrant the use of traditional control mechanisms such as switches. Nevertheless, equipment manufacturers are keen to update both the functionality and cosmetic aesthetics of their products. Industrial automation equipment is increasingly networked.”


Clearly, when it comes to home automation, there is a need for an integrated display and control center to control heating, ventilation and smart-energy monitoring.

“You need a higher performance microprocessor, but with a more intuitive, easy-to-understand user interface (UI). When embarking on a new control panel application, embedded developers are likely to select a microprocessor device rather than a microcontroller,” says Gaillard.

“This is dictated by the processing power required for the connectivity and the need to manage a TFT LCD screen and associated UI. An example of such a microprocessor is the Atmel SAMA5D3 MPU, based on an ARM Cortex-A5 core. It’s 65nm low-power process geometry delivers up to 850 DMIPS (drhystone million instructions per second) at 536 MHz and up to 1,328 MB/s at a 166 MHz bus speed.”

The SAMA5D3 also features a floating-point unit (FPU) for high-precision compute-intensive applications, along with a 24-bit TFT LCD controller and graphics accelerator for image composition. Optimized for use in industrial control and HMI (human-machine interface) applications, the device is equipped with a comprehensive set of peripheral interfaces including dual Ethernet, high-speed USB and dual CAN.

Simply put, the Atmel SAMA5D3 MPU is an ideal candidate for most control panel-oriented designs. With its Cortex-A5 core and vector FPU, the MPU is capable of achieving accelerated graphics processing. Coupled with the 32-bit DDR (dual data rate) controller performing up to 1,328 MB/s, it offers enough raw horsepower to drive a high-resolution screen display via the 24-bit TFT LCD controller block. Resistive touchscreen support is integrated into the device, although one can alternatively interface to an external Atmel maXTouch capacitive touchscreen controller.


On the software side, Atmel has partnered with TimeSys to port the Qt framework and its comprehensive range of development tools for easy UI design. Qt can best be described as a cross-platform application framework with a reliable, easy-to-use toolkit to develop complex graphical user interfaces.

“Qt is based on a comprehensive set of widgets that you use to create a GUI screen design. Within the Qt Creator development environment, the Qt Designer tool allows you to lay out the interface design and plan the human interaction,” Gaillard adds.

“The excellent support for multimedia and 3D graphics, plus all the traditional concepts of text entry, check-boxes, and radio buttons, all help to facilitate the easy creation of industrial interface designs. Indeed, the Qt Designer creates C++ code that integrates into your application, while QML defines all the necessary visual graphical interface elements to create and animate visual interaction.”

Interested in learning more? Check out Atmel’s official white paper on the subject here.