Jan 28, 2014

Invensense Microphone Skips a Step

posted by Bryon Moyer

The number of microphone output options just got bigger by one.

Typically, there have been analog microphones, where you get a real-deal audio signal to play with, or digital microphones. The question is, for the digital versions, what does that mean? How are the 1s and 0s to be interpreted?

Says Invensense, up to their latest release, all digital microphones take the audio signal, digitize it, and then run that signal into a codec that creates a PDM signal. For anyone not steeped in this stuff (including yours truly), PDM is “pulse density modulation.” In other words, the number of pulses-per-unit-time relates to the value being communicated. More pulses = higher number.

There are actually other potentially confusing PxM formats. PCM – pulse code modulation – is more or less the strict sampling result of an analog signal. It’s got a role in storing music on CDs, for example. PWM – pulse width modulation – is what you get if you take PDM and, instead of having discrete pulses per unit time, you abut them – that is, instead of five separate unit pulses, for example, you run them together to create one pulse five units long.

Most systems expect PDM signals in I2S format from their digital microphones. And I’ll be honest: when I first posted this, my mind mapped I2S to I2C.  Which is incorrect. I2S is used to interconnect audio devices. Invensense sees an opportunity with some systems that take audio in but have no audio out. May sound a bit strange, since most audio is done for the pleasure of our ears. But, increasingly, we’ll be able to use sound to control our systems. So a smart watch or some other kind of wearable gadget might respond to our voice commands or other audio cues. They have no speaker, so they’re not reproducing sound for us; they just consume it.

And, apparently, such devices don’t need PDM. So, using typical digital microphones, they’d have to take the encoded data and decode it. Invensense has a new option for them: a microphone that simply skips the encoding step. What you get is the direct filtered output of the ADC, formatted for I2S. The idea is that this simplifies the design of the gadget.

Figure.png

 

You can get more info in their announcement of solutions for always-on wearables.

Meanwhile, the next day they also announced a new analog microphone…

 

[Editorial note: this was updated to correct the I2C vs. I2S error, as noted in the above.]

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Jan 24, 2014

Ten years and rolling

posted by Dick Selwood

Ten years ago today the Mars Rover Opportunity bounced its way on to the surface of Mars, at the start of a three month mission. In that time, as well as driving 24 miles, the little machine has added enormously to our understanding of the history of the planet.

And this is a huge endorsement of the team who put together the electronics. The development process started nearly twenty years ago, and by the time the mission launched most of the electronics used was, to put it kindly, mature. The central processor is a 32 bit Rad 6000 microprocessor, a radiation-hardened version of a Power PC that was launched in around 1965.

Just look around- how much of the electronics you own is ten years old and still functioning? What software are you using that ceased development around 15 years ago.  That is a little unfair since the software on Opportunity has undergone several upgrades.

That in itself is quite mind-boggling. When did you last do a major software upgrade and how easily did it go?

This week there was another space event that was a tribute to system designers. The Rosetta mission to investigate comet Churyumov-Gerasimenko woke up after 31 months in hibernation mode the latest stage in journey that started almost ten years ago.

So It is possible to create systems that last for years- you just have to work hard at it.

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Jan 23, 2014

TSensors Roadmap Takes Shape

posted by Bryon Moyer

Last fall, an effort was started to drive the MEMS business (or sensors in general) to the point where a trillion sensors are shipped yearly. We covered the TSensors event, and we promised to update.

As a quick recap, the approach here is to identify high-yield applications and then focus in on those to remove barriers (largely, but not exclusively, cost). So the current process is to establish what those applications are going to be, and then have a chairperson for each application driving the writing of a chapter, to be contributed by various people.

The topics selected are as follows:

  • Noninvasive fitness-wellness-health monitoring (possibly to be expanded to include animal health)
  • Noninvasive chronic disease detection and monitoring
  • Minimally invasive fitness-wellness-health monitoring (possibly to be expanded to include animal health)
  • Personal imaging
  • Computer sensors (smell, taste, color, biometrics, etc.)
  • Environment sensing
  • Sensors for food production
  • Smart grid/Energy/Harsh environment sensors
  • Energy harvesting
  • Ultralow power wireless communication
  • Network infrastructure for Internet of Things

That’s a lot of stuff, covering a lot of ground.

One thing that’s clear is that there is room for more contribution by authors and even chapter chairs, at least as of the last update I saw. So if anyone is interested in participating, contact information is available on the TSensors website.

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