Prototype is in!

A project log for Team Ides: DC27 / da Bomb!

A wearable, hackable, blinky badge for Defcon27 featuring RGB leds, sound, BLE, games, and more!

John AdamsJohn Adams 03/25/2019 at 02:340 Comments

Oh man, it's here, and we've got about 95% functionality. Bask in its programmed glory... 

The only mistake I really made was in the fuel gauge circuit, which I got completely wrong. The footprint on the chip was no good, and they couldn't place that. Without the chip in place, our power circuit didn't function. Some how I was also shorting the battery to ground through a 0.1 ohm resistor, so that was really fucking smart. oops.

Removing R403 solved battery power, and the board came up. All systems, as we know it, are functional and we have some minor changes to make the badge production ready. 

We've also ordered a bunch of speakers to test with from digikey and mouser to see if we can find better speakers. The best speaker wins, and that's what we'll go with for final design.

Everything we've tested so far sucks, and sucks badly. I'm unhappy with the 200mW amplifier but we have hit the limit on our battery budget and parts to go to a bigger amp. I am hoping that larger speakers will help a lot. Anything is better than the weak-ass 100mW amp we had in 2017. 

Bill writes:

I spent most of yesterday at John's place doing more testing and fixing with the badge prototype.

The good:

The not so good:

I think we definitely need to move the screen over to the left a few millimeters so that it's not so close to the front button pad. But this is a huge headache: it means moving the 40-pin connector and all 4 screw holes for securing the screen, and doing that means having to relocate a bunch of other stuff too and re-routing it all.

Also, now I have to write a BLE GATTC client module. I already have a GATTS module which provides attributes with characteristics which can be read and written, but so far I've only tested that from my phone using the nRF Connect app. I want the badge to be able to do it too. Using this I can more easily send notifications from one badge to another. It looks like a bit of a pain in the neck to implement, but that seems to be par for the course for Bluetooth.

On the whole I'm pleased though, because now that we know the bling works, it means that the prototype had zero assembly glitches from Macrofab, which hopefully means we'll get a much better yield this year.

The next step is for John to rig up some quick code to make the LEDs do something neat and film a demo video so that starts may be kicked.