Wednesday, June 21, 2017

The Rabbit-Hole of Atmel Fuses

So, you've just got your Atmel-ICE Debugger and you're rarin' to go. You follow the step-by-step, wait, there are no step-by-step instructions.

You finally resort to plugging things in at more-or-less random, fire up Atmel Studio and blunder your way through creating a new project, importing blink and compiling.

Eventually, by a combination of persistence, web searches, document-diving and sheer chance you come upon this window:

Let me point out a couple of things that might save you some heartburn. First off, an empty checkbox means enabled. Neat, huh?

Second, the HIGH.SPEIN can be disabled, but once you've done so there is no going back without a high-voltage programmer. You get a warning as shown in the screen cap, but the warning makes no mention of the permanent nature of the change. My muddled understanding is that the fuse is set to prevent re-programming of production units. A neat feature but so poorly documented that you'll probably brick one or two MCUs before you get the point. I can still program my sacrificial Arduino Mega via Atmel Studio and the ICE but programming via USB no longer is an option.

I'm not alone in my bewilderment and frustration with Atmel. Watch this video and listen closely, particularly his instructions at 2:22.

Pay heed or pay for a high-voltage programmer.

Sunday, June 18, 2017

Inside a DHT 11

If you've ever wondered what's inside a DHT 11 temperature/humidity sensor, I'm here for ya'.

Resistive humidity sensor in a DHT 11

The die is about 1/16th of an inch across. Click the picture for a larger version.

Don't ask me how, but I managed to kill the three sensors I had around from various kits. In the process of building a remote temperature/humidity IoT node, I was able to test all three. I even swapped out the NodeMCU the node is based on with no joy. I bought a DHT 2 to replace it (livin' large, 7 bucks vs. 2) and that works so I figured I'd dissect this one for science fun.

There's an unmarked chip on the back and a thermistor somewhere in the package.

That's a 'yay', but of course a small one.

Friday, June 9, 2017

Let's Get Small

I got a new toy and brother, this thing is a blast. It's an Opti-Tekscope OT-M HDMI Microscope with Camera and it's as much fun as you can have with your clothes on. 

I've always loved looking at pictures of small things and have often wished I could see some different things under a microscope. This microscope does what I got it for (identifying and soldering small parts) and it's a fair compromise between cost and capability.

So let's look at something small!

TCS34725 by Mark Turnauckas on
You can see the full-sized version of this photo here. It's worth a look.

Above is a photomicrograph of a Color Light-to-Digital Converter with IR Filter from AMS. It can be used in things like robotic sock-sorting machines to differentiate different colored socks. I'm working on such a machine now. Since all of my socks are black I'll bet it works.

There are small light sensors under the color filter squares. The light intensity of each sensor is combined and converted to a digital signal that is sent to a computer or microcontroller.

Below is what it looks like mounted on a breakout from Adafruit. The part in the photo above is outlined in green in the photo below.

The sensor on a breakout in my palm.

Each colored square in the photomicrograph is about 0.004" across. I don't know what that is in human hairs but it's pretty darned small. There's also a lot of other things built right onto the chip, which is pretty amazing.

So there ya' have it. Yay for small!

More about the AMS color sensor can be found here.