Monday, August 29, 2011

Software defined... Radio, GPS, ... etc?

Most comms modules (e.g. Bluetooth, GPS, etc),  memory peripherals (e.g. SD cards, USB sticks, etc) and other sophisticated "chips" have embedded processor cores. These cores may be based on stock 8051 or specialized ARM designs.  They are smart devices that save system designers a lot of integration time by being "drop ins" (i.e. you talk with them via simple protocols over UART, I2C or SPI) and they do all of the hard work.

Recently, reading about Software-defined Radios (replacing hardware based tuning/filtering with software) and this article (dumber GPS modules where satellite correlation/fusion is done by back end computers), makes me wonder if the future will present dumber peripherals in trade for more processing on our main CPUs.

How many processor cores are there in an average smart phone? You've got the primary CPU running the OS, but have you considered what is powering your Bluetooth, Wi-fi, GPS, cellular modem, display and touch interface?  Having sophisticated software in these peripheral chips certainly aids time to market (less programming for the integrator).  But, I rely on the craftiness of the chip designer to meet my needs.

Sure, its all software (even when on individual hardware modules), but rarely are these things upgradeable. They have a limited product life (even if the analog part of it is still relevant).  This is good for hardware companies, but not good for us (the end user/consumer).  

I remember playing with early MEM accelerometer chips. They usually just output a voltage for an axis. There were no "interrupts" or SPI or I2C protocols. They were analog devices. It was up to me to figure out what they were spitting out and deal appropriately.

Now I use smart digital accelerometers that notify me when an event (e.g. tilt, acceleration exceeding a threshold, free fall, tap, etc) occurs. Sometimes they can be frustrating if they don't quite provide what I need -- lots of register based tuning usually takes care of this, but still...

Imagine a smart phone where all of the processing was done on the main CPU. Sure, that would bog it down significantly, but imagine a much faster (and power efficient) main CPU (maybe even with 4 or 5 cores).  Now, your GPS/Bluetooth/Cellular-modem are just  analog transceivers that streams bits or analog signals.  Your smartphone would just have a bunch of antennas, transceivers and sensor hardware. All of the software resides somewhere on the main CPU. Imagine having access to that software.

Wednesday, August 03, 2011

UV Index monitor prototype #1

I don't know if I mentioned it here before, but I've been working on a personal UV (Index) monitor.
Folks who have skin cancer (or those at high risk) need to make sure they limit their sun exposure.

The general approach is to just lather up with sunscreen every time you leave the house, but this is impractical (plus you have to re-apply every couple of hours).  This becomes more of an annoyance when you consider spending hours riding in a car: Are the windows UV protected? How well? Do you have to lather up every time you drive?

You can get UV index forecasts on your smartphone, but these are just forecasts (for your area and for the whole day). When you are out in the sun, you'll need to know how much UV intensity is hitting you  "right now".

Another solution is to carry a UV monitor.

The only ones I've seen on the market are overkill (too large and complex) or vague (how does this work and is it reliable -- where is the sensor?) .
I am aiming at something so small that you'll always carry it with you, but also clear and as accurate as possible.  My target form factor is a key fob:

My target UI is based on colored LEDs. There are official colors for the UV index scale and I have an LED for each level.  I would like to have (at most) 2 buttons -- one for "instant read" (point at the sun and an LED will light up for 2 seconds indicating UV index level) and one for setting a countdown timer (for sunscreen re-application).

My current prototype has 1 button, 5 high-intensity LEDs (green, yellow, orange, red and blue/violet) and is a little bulkier than a key fob. Amazingly, the LEDs are quite readable in bright sunlight! If you are colorblind you can always read index based on which LED lights up (right?). The current layout ramps "upwards" depending on UV intensity.

It takes a single coin cell battery and is based on a very low power 8051 from SiLabs. It should get 3-5 years off the battery with casual usage.

I need to do lots of tuning/calibration and I know it won't be "demo worthy" for the rest of this summer, but I am making progress.  Apparently, the calculations done for UV Index forecasting aren't very practical for small single UV sensors. Somehow, the personal UV monitors make due though.  I think I'll use one of the better ones to aid in my calibration.

Maybe I'll have case design and a formal board spin ready for next summer?