A situation many can relate to: an empty smartphone battery and no outlet around! That’s exactly why I recycled an old laptop battery into an USB power bank.
This article will show you the basic powerbank circuit consisting of Lithium cell charging circuit, boost converter and toggle switch as well as my improved version with self activating boost converter and LED status indicator and homemade housing.
The glasses themselves are based around an STM32F051K8 microcontroller (LQFP32 for easy soldering!). All the firmware is custom written though I got the LCD driver initialization codes from the BuyDisplay examples. The firmware is written using a somewhat “co-operative scheduling” with interrupts methodology and for most of the time, the microcontroller is sleeping until something needs to happen. Along side all the Bluetooth and LCD software, I’ve included my SoftTouch library for the two touch buttons on the side of my glasses. These are used to change screens and change items within the screen e.g. move to the next news entry.
Karl Hagström wrote an article detailing how he hacked the stereo (HU-650) in his Volvo V70 (2007) and added his own AUX input:
Why, why, why isn’t there an AUX input on my car stereo from 2007?
Yes 2007 was before the big era of smartphones, but everyone owned a couple of dirt cheap mp3 players and iPod was a big thing.
The HU that my car is fitted with has two super retro 8-pin DIN-connections on the back. One of which is for connecting a CD-changer “CD-CHGR” that you could have installed in the boot of the car – but who uses CDs these days?
It didn’t take allot of research to find out there is already a product out there that lets you add an AUX to you HU-xxxx. The only drawback is that it sets you back $80 and most of all: It doesn’t come with the awesome feeling that you get when you have hacked the stereo yourself.
Thanks to a tip of my reader, I found a relatively cheap (69Eur) Android box with HDMI input and record ability. I thought that it should be possible not only to record the HDMI input but also to stream it in realtime so I ordered one for experimenting.
Turning a USB to RS232 adaptor into a USB to TTL serial adaptor by Aaron Brady:
I didn’t want to wait, so I had a look around what we had on hand. We did have a spare RS232 to USB adaptor. This one speaks the full ±15V, and I briefly considered using one of the spare MILSPEC SP232’s we got cheap to bring it down to TTL, but that seemed mad: there was going to be a MAX232 or similar in the serial adaptor bringing it up to voltage so it could go a couple of centimetres before getting stepped down again.
Here begins our adventure into very small wires, fine SMT soldering and hot glue.
We popped open the case, and there were two main ICs, a Prolific 2303 (the USB to Serial IC) and a ADM3251E (the RS232 line level convertor). I tried to desolder this with no success, but Bas stepped in, cut the leads with a craft knife and ran the iron over the chip’s leads and it basically fell off. He also did the very fine soldering to pins 1 and 5 of the Prolific chip, TX and RX respectively.
As part of a prototype developed 12 months ago I was tasked with reading measurements from a blood pressure cuff [sphygmomanometer] in real time. Not surprisingly there are no consumer level devices that have a serial interface because what ‘normal’ person would want such a thing!
Initially we considered our own interface for a blood pressure cuff. Just run the pump and take the readings with our own processor and pressure sensor, how hard can it be. Rather difficult it seems, the processing and knowledge required to develop a device to perform even rudimentary readings would have completely blown the time budget. Instead we looked to hack an existing device, enter the Omron RS8.