How low is low power?

A buddy called up asking me the minimum power consumption of Atmel chips. He has an application that has to be battery powered and it just can’t suck much more than the self-discharge out of the battery. I had another application years ago with the similar problem. I was trying to steal power from a phone line to run a little micro. If you look at the very strict laws, you are only allowed about a microampere out of the -48V POTS (plain-old-telephone-system) line.

So the trick is to steal the microampere continually, and let it charge up a big capacitor, so your micro has more than a few uA to run on for a little while. My buddy had a pretty high battery voltage. So with a switching power supply he can take in 1 uA at 24V and make 10uA at 2V that will power the MCU. Better yet, you can put the system to sleep or all the way into power-down, and only wake it now and then. With a 1% duty cycle, your 10uA continuous current can instead become 1mA when you are in wake mode and 0.1uA the other 99% of the time.

So back to the task of figuring just how low a low-power AVR chip is. Since this is a hardware issue, and you only have to worry about hardware once in your design, the salient info is towards the end of the datasheet. And you do have to dig up the “full” datasheet, not the summary version. CMOS microprocessors use power in direct relation to the clock frequency they are operated at, as well as the power supply voltage you run them on.

So I started with the smallest physical part we make, the ATtiny13A . It is fully static. On page 126 they actually have a 2-dimentional power consumption graph, but the first one shows 100k-1MHz active clock. Scroll down to page 127, and Figure 19-6 shows 32kHz clock figures. The part sips about 7uA at 2V Vcc. Then scroll down for idle power—Figure 19-12, it’s about 1.2uA. Then more scrolling and you get a power-down consumption of 0.1uA with no watchdog, and 3uA with the watchdog.

My suggestion is to let the switching power system run the show. Have it gently steal power and when it has charged up a big ol’ ceramic cap, then have the power system take the MCU out of power-down, (not idle) do the measurement, and either kill itself or handle the alarm. This part does have a 10-bit ADC so you have to look at the time it takes to get a good conversion out of it.

This can get really tricky. My buddy Nick Gray noted that sometimes you are better using a faster ADC since you can get a good conversion out of it in less time, so the duty cycle of “on” goes down, and you end up using less power despite having a higher-current ADC. Same deal here— you need to think in Coulombs—what is the fewest number of electrons needed to wake up, do a test, and go back to sleep.

In any event, it is obvious that you can set up an AVR system to draw less than the self-discharge rate of your battery system. Note that if you need to do 500MHz processing, well all bets are off. The speed-power tradeoff in semiconductor devices is pretty absolute, so don’t think you can do HD video on a uA.

How low is low voltage?

How about 1.8 volts +/- 10%. Yeah, I was reading a flyer about Atmel’s 32-bit AVR® UC3 chips with picoPower® technology. It points out selected devices will work off this low of a voltage. That means a couple of alkaline batteries that are almost dead at 0.9 volts will still power the chip. The flyer points out that the AVR UC3 will do 70 DSP functions, more proof that you don’t need those power-hogging DSP chips from our competitors to run your system. The UC3 chips also do peripheral DMA (direct memory access). This means you can hammer the SPI and USART at 33Mbit/s and the CPU will only be at a 15% load.

There is so much more to evaluating micros than clock speeds and pin counts. Take the time to learn about all of Atmel’s offerings, and you may find the perfect chip to get your job done.

Death of the DSP

OK, so that title is intentionally provocative. The DSP is not dead yet. But as I learn about Atmel’s ARM processors, I ask myself why I would ever use a DSP chip. The Atmel Cortex M4 has single-cycle multiply accumulate. It’s got floating-point math. Its pin-to-pin compatibility with Atmel SAM7S, SAM3N and SAM3S microcontrollers. The CPU has DSP extensions. And Atmel parts sip power compared to traditional DSPs. One of the coolest features in parts like the SAM4L is how you can set up the peripherals to operate and even write to memory without waking up the core CPU. So all these features plus the appeal of ARM compatibility is putting a lot of pressure on those older DSP chips. When you look at the power of the AVR and ARM chips Atmel makes, most all of them have the power of the old DSP chips, and they get the job done using less current.

Xplained is the new Butterfly board

I was in a startup in 2001 when I first designed in Atmel products. One of the big enticements of Atmel was the really cheap demo board. Back then they called it a Butterfly board and it cost $49. Now we have things like our Xplained series evaluation kits. They are still low-cost, and they they can give you a big head-start in getting code written for your next project.

The Atmel starter guide gives some great advice on how to become instantly productive with AVR and ARM parts.

1. Download and install Studio 6
2. Check out some examples of similar things
3. Buy an in-circuit debugger– $49 Dragon, or $99 JTAG ICE, or the $599 AVR ONE!
4. Buy an eval kit, a starter kit,  a touch kit, a wireless kit, an evaluation kit, or a reference design.

This is the great thing about Atmel, for a really low cost you can have some hardware up and running. I plan on digging out my old Atmel projects and open-sourcing them for the community. Stay tuned to the Atmel Bits and Pieces.

The Silicon Valley eFlea electronic flea market breakfast

So after the Silicon Valley electronic flea market, we go over to Bobbies breakfast bistro and compare purchases and catch up on the scuttlebutt. We get there about 9:30AM. Here are a few snaps of recent items. Note that the eFlea closes in the winter, from October to February, but we all still go to the breakfasts, just to keep up on recent happenings.

When Hans Camenzine died several of my pals gave tribute to the inventor of the 555 timer chip, the biggest selling IC in history. Here is Kenneth Finnegan with Han’s book, and a T-shirt David L. Jones did to honor him.

My buddy Eric Schlaepfer built a 555 out if discrete transistors in honor of Hans. It also honors Jim Williams, who did similar functioning electronic art.

Here is our pal Richard King, who is over at power storage startup STEM. At the bottom you can see the 1862 telegraph pole wire anchor, something he inherited from his grandpa. We always bring some show-and-tell to the eFlea breakfast.

Brocade employee Rob Bowers brought a series of Ham radios he has owned over the years, to highlight the enormous cost reductions and size improvements.

Audio guru Steve Williams often snags early publications, like this Sam’s photofact.

Here is some radio craft magazines that Steve found last year at the eFlea.

And crack mechanical engineer Dave Ruigh shows off his admittedly half-$#%ed antenna kludge so he can better download Top-Gear episodes over his 4-G hot spot. He says it even works in his glove box. He has gone on to design something a bit less unsightly, but you folks know how prototypes look, so don’t give him any guff.

Here pro photographer Vini Carter looks at a mystery gizmo that Richard King found on eBay. Eric Schlaepfer is in the background, doing what Google employees love to do, fiddle with their Android. Vini is the guy that restored a sulfur dioxide refrigerator. His wife makes him keep it on the back porch, and Vini agrees that is probably for the best. If you see the haz-mat trucks in his neighborhood, you will know the deicing went all wrong.

So see what I mean about a fun time for all on the second Saturday of the month here in Silicon Valley? If you can’t drag yourself out of bed at 5:00AM, feel free to just show up for the breakfast. There are usually 12 or so people that make the breakfast, but there is always room for more.

The May 2013 Silicon Valley eFlea electronic flea market

The Silicon Valley electronic flea market, dubbed the eFlea by my pal and long-time attendee Dave Ruigh is this Saturday, May 11, 2013. My buddies and I try to get the eFlea by 6:00AM. Then around 9:30 we go over to Bobbies breakfast bistro and compare purchases and catch up on the scuttlebutt. We are often still gabbing by 1:00PM. There is a 3-dollar parking fee at the eFlea—you have to get a ticket out of one of the machines or you get a real ticket for 35 bucks. If you want to sell it’s still only 20 dollars for two parking spaces inside the market.

Be sure to get to the eFlea at the crack of dawn if you want to scoop up the really good stuff. Many attendees carry powerful LED flashlights to help pierce the darkness.

Because I go to the eFlea with my totally cool pals, they tip me off about toally cool gear like these Blonder-Tongue units.

My EE buddies are always looking for test equipment. Here is a nice HP signal generator. That is why you used to see Jim Williams and Bob Pease at the eFlea. Bob Dobkin, the founder of Linear Tech is there most months, as is Dennis Monticelli from TI.

Here is a nice Tek scope. There are scads of test equipment every month. Hey, something has to compensate us for living in this over-priced hell-hole called California.

There is a fellow who deals Metcals and every other type of soldering equipment you can think of. The eFlea is where you get that 0.010 lead solder.

Ya can’t design it if ya can’t see it. All my pals have an assortment of visual acuity enhancers, everything from eye loupes to these zoom inspection microscopes.

And here is a modest selection of power tools.

Well, you get the idea and see why it’s a good thing to show up early. Next post I will talk about our breakfasts at Bobbies and the cool gizmos we find.

Rako starts at Atmel

Some of you might recognize me from my previous job at EDN magazine. I covered the analog beat. So many of my friends were surprised to hear I was joining Atmel. What they did not realize is that being an analog expert is only part of what I love. I ran a consultation business for 20 years. My specialty was designing, prototyping and delivering working hardware. One of my favorite jobs was in 2001, at a startup where I designed a complete point-of-sale terminal in only 2 months. I knew I would need help doing the software, so I called my friend Dave Mathis. He agreed to write the code, but only if I used a modern micro. Not knowing any better, I suggested a well-known micro. He said he would quit if I used that hardware. He refused to program one, after more than a few bad experiences. Then I figured we could use an 8051 clone. He said that he really did not want to deal with special function registers. OK, this was going nowhere fast, so I asked him what he thought would be a good embedded processor. Dave had written Forth compliers for Samsung micros, so I didn’t know what to expect. He said I should check out Atmel. I did. I was impressed. I had been exposed to Atmel micros when I was consulting to HP. They ran wicked fast and did not need 8 clocks to execute an instruction. The other thing I loved is that I could get a Butterfly prototyping board for $49.95, and a real in-circuit emulator for $200. When you are in a startup in angel-investment mode, that low barrier to entry really means a lot.

So I picked a nice little AVR micro that did everything we needed and more. I wrote the assembly language firmware for the point-of-sale terminal as well as some other products we developed. I hired two buddies to write some C code. I see why Dave recommended Atmel. Wags have joked: “The best programming language is the programming language your best programmer likes best.” I really like the Atmel development system and the chips worked great. Both buddies have gone on to love and use Atmel micros in their projects as well.

So I am really looking forward to document how Atmel can make your design work go better. I will be getting up to speed on Atmel’s touch technology and will share with you what I learn. I am also looking forwarded to getting into the ARM controllers. That is some heavy iron to an 8- and 16-bit guy like me, but my buddy Dave will point me in the right direction and I am sure my co-workers here will put up with my questions.

When Sander Arts asked me to join him at Atmel, the first thing I did was call my pal Dave. We thought Atmel was cool and we knew it 13 years ago. But I was not sure of how Atmel was doing in the eyes of the world. Dave said “Atmel’s star has really risen in the last 5 years.” The Arduino was part of that. But he said people were also seeing how cool the Atmel ARM stuff was. And the whole world was seeing what Dave saw in 2000, how Atmel can get you into 8-bit development cheaply, and how nice the code works. When I was at the Design West conference this year (2013) I saw my buddy Windell Oskay, the co-founder of Evil Mad Science. When I told him I was starting with Atmel he was really jazzed. He said that he loved the Arduino and the whole development ecosystem that has sprung up around it.

In addition to telling you about all the cool things Atmel is up to, I will be sure to keep you informed of all the fun things my pals are doing. This includes lifestyle things like the electronic flea market here in Silicon Valley and career things like how my crack protégé has figured out a LinkedIn profile that gets him 3 headhunter calls a week. Stay tuned and look for all the system design scuttlebutt that will help you be a better engineer and programmer.