Kinko's and The Keychain

I purchaed a picture keychain at Kinkos because it had an OLED, and got more than just a keychain.

Backstory

I had to go to Kinkos to get my documents bound. A coil binder is just not something which I can justify keeping at home. Unfortunately, this always involves waiting for about 20 minutes. This is not long enough of a time for me to be productive, but just long enough to feel wasteful. Perusing the isles at Kinko produced an unexpected find: an OLED. The best part was that it was on sale for $12. The OLED interested me for the following reasons:

OLED was small and color
power circuitry
noise
USB-powered

OLEDs take about 10v of backplane power, and I've been curious about implementation of the power circuitry. I was also curious about the supplier of the OLED, so I purchased the keychain. Oops, did I mention that the OLED was packaged in a keychain? (This keychain is now colloquially referred to as The Keychain for reasons which will become clear later.) So, I purchased The Keychain and cracked it open right there in Kinkos. I got the case off, and made some notes on the ICs. At this point, my coil binding was done and I had to head home.

Probing around

I decided it spend an hour poking around at the circuitry since I had an hour to burn. I also have a pretty nice lab at home, so I did a postmortem on the device. In summary, The Keychain was probably on sale because it was terribly designed. The battery was inadequate as it could not sustain the power draw required by the 11v charge pump for the OLED. This meant that the device could not illuminate the OLED if not plugged up to USB power. The USB bus would draw more than 500mA if the device was powered on and the battery was charging. The device was so noisy that I could see it inducing blips on one of my picoammeters. The lowest bidder wins the economic race, so they probably thought they'd made a million off the design reductions, but they were a bit too extreme. Anyway, I learned at least the $12 worth of information, so the purchase was worthwhile.

Adding a picture

Before pitching the device, I figured that I should put a picture on it to see the quality. As an afterthought, I wanted to see the total current draw of the OLED with all of the pixels being white. I installed the software which came with The Keychain and it was the sort of terrible quality software which you expect, and I proceeded to upload a graph which I had handy, which happens to be Figure 1.

Figure 1. I really like this picture. Brian Gestner generated this for one of his papers, and it illustrates the difference between theorists and engineers. It's the mean time to overflow based upon integer bits for a 4x4 MIMO system. If you are a theorist or a mathematition, you'll want the mathematics to be beautiful and perfect. In the case of this system, it requires about 12-bits if I recall. If you are an engineer and putting it into silicon, you realize that multipliers take up space, and that 4 billion years between errors should be about enough time to satisfy anyone...unless you are getting your engineering paper reviewed and rejected by a mathematition. 4-bits should be adequate for everyone else.

The first thing the software did after uploading the file was generate an error and crash; however, I noticed that The Keychain had changed modes and it now said that there was 1 picture present and was showing the MIMO graph. I proceeded with my tests and was pleased by the fact that the current consumption by the OLED only 2uA different between the blue "no picture" screen and a white background.

I ran the upload software again and it confirmed itself as a terrible bucket of bits by connecting to The Keychain and showing that there were zero pictures uploaded. I putzed around with the software and it basically only seems like it could upload and crash (it crashed when you clicked on menus besides the upload button), but I didn't have any other non-eps pictures handy to use with the software's one function , and I have had enough of it in general.

Easter Egg?

The next time that I looked at The Keychain something had changed. Somewhere between poking at the circuit board and running the crashtacular software, the picture count had increased from 1 to 5. Scrolling through, I found that I had the MIMO graph and 4 pictures of some cute asian girl. Figures 2 and 3 are two of the pictures which came from the device.

Figure 2.

Figure 3.

Thoughts

I think that some combination of probing around on the board, and crashing the software, I must have unleashsed this easter egg. Surpised yes, offended no.