Tag Archives: 1M Ohm resistor

Vegard Wollan on the AVR and ARM cores and peripherals

In the fifth video of the series, I asked the co-inventor of the AVR microcontroller about the progression of the peripherals in the various microcontrollers Atmel offers. Vegard shares that when they invented the first AVR products, the team was concerned with ease-of-use, a clean instruction set that would run C, instructions that ran in a single cycle, and good quality tools.

However, he was just as proud of the peripherals that they then developed for the XMEGA line of AVR 8-bit chips. There, he said the stress was still on low power, but also a set of peripherals that were high performance, robust, strong, effective, and that included analog and digital advanced peripherals. Additionally, Vegard stressed how the XMEGA event system would allow programmers to handle complex events and take action, all without waking up the CPU core in the part.


Vegard Wollan becomes animated when talking about the peripherals in AVR and ARM chips offered by Atmel.

I knew this was cool for the low-power aspect, yet Vegard reminded me that it also allows you to service an interrupt faster and more deterministically — always a good thing in embedded systems. The great news for engineers is that all the cool things Atmel figured out for the XMEGA AVR also went into to the UC3, the 32-bit AVR product lines. Then, we made sure to put these same powerful and flexible peripheral systems into our ARM core-based MCUs. In addition we would add dedicated touch I/O pins and more accurate clocks and references. You can still see the AVR DNA from back in 1990 at the Norwegian University of Science and Technology where the AVR came to life.

What I really loved about Vegard was his humility. Every time I tried to give him credit for the AVR he was sure to remind me that there was a whole team that developed it. And, when I tried to point that the AVR was RISC (reduced instruction set computer) before ARM came out, he told me that he was more proud of the peripherals in all of Atmel’s chips, rather than just the core he invented for the AVR. That’s a good thing to keep in mind.

While using any ARM core will get you the instruction set and header files and open-source tools, Atmel’s ARM chips will also get these great peripherals and the event system to tie them all together, while the CPU sleeps peacefully. A recent article helped me understand Vegard’s Norwegian modesty, but I am sure glad he and his team worked on the AVR and ARM chips.

Activating a PC with a knock and an ATtiny

A Maker by the name of Joonas has designed a knock sensor to activate his PC. According to the HackADay crew, the entire project cost Joonas a grand total of $10 and is built around Atmel’s ATtiny45 MCU which is tasked with emulating a PS/2 device.

“This takes advantage of his computer’s ability to boot upon receiving PS/2 input,” HackADay’s John Marsh explained. “The build uses a Piezo buzzer and a 1M Ohm resistor as a knock sensor exactly as the official Arduino tutorial demonstrates, [plus] one of those PS/2-to-USB adapters that are most likely lurking in the back corner of every drawer in your office.”

In addition, says Marsh, AVRweb was used to disable the 8X clock divider so there would be sufficient clock cycles for PS/2 communication. Joonas subsequently loaded some test code (final version posted to Github) to ensure the vibrations were being detected correctly.

Readers of Bits & Pieces may also want to check out a recent article about a Halloween Knock Box powered by Atmel’s versatile ATtiny45 (or 85) microcontroller (MCU).

The box is fairly easy to put together, as basic components include an MCU, a piezo element (amplifier) for the knock sensor and a motor to provide the knocking feedback.