Building a PCB lapel

The completed lapel!


A while ago, I chanced upon a satirical “boy scout badge” featuring the text “Centered vertically in CSS” by @mrgan.

I had little experience with fabric, but building a lapel out of PCB seemed like something that might just work. PCBs are typically built with extremely high tolerances for its copper and mask layers and still acceptably accurate for the silkscreen.

Hopefully this post documenting my build process will be helpful if you’d like to give PCB lapel designs a shot!

Disabling updates in MacsFanControl (by replacing a byte)

MacsFanControl is this utility that enables manual controls for my Macbook’s fans on Windows. Recently, I had the unpleasant chance to interact with their update mechanism.

Update pls

The update prompt must be acknowledged, and there is user-configurable option to disable or ignore the updates. Considering the app works just fine as it is, along with the fact that future updates will still have this issue, I chose to disable the updater permanently.

Adding new, undocumented features into a kernel driver

Note: this is a recollection of my memory (and source files) from about 2 years ago AX88179 USB3 Ethernet device

How would I go about changing the MAC address (permanently) on this AX88179 USB 3.0 device without breaking it open?

I found myself with an unusual challenge - the MAC address of many networking devices, if not already burnt into One-Time Programmable memory, could possibly be stored in an external (rewritable) EEPROM. Breaking open the device and directly accessing the EEPROM would be trivial, however I was unwilling to scuff the glossy plastic enclosure; I sought to do this without dismantling the device.

Defeating wireless fixed code systems with just US$23

Doorbell being triggered Wireless doorbell being triggered. No, it’s not someone else’s :^)

Fixed-code wireless systems are not unlike having someone shout a specific password to open a door (or anything else) with a certain pitch and speed, except that this occurs in the electromagnetic domain instead of moving air.

This can be best described as “security-by-obscurity”, or, hoping that others are unable to capture and replay the signal. However, readily-accessible and affordable hardware is now within reach of most. As of writing, US$23 nets all the required parts to do just that.

Radio Frequency shares much with sound, so this post will attempt to draw similarities between them. Lets get going!

Hacking the NDP Pixmob bands - How I got the LED band to run my code

It lives!! hehehe

The NDP 2016 Pixmob band - thousands mesmerized, documented by many, but still not hacked to run custom code.

This (fairly lengthy) post documents how I learnt about the ISP protocol, built a board to implement it and integrated it with the Arduino IDE.

The Pixmob band

Pixmob band as-is

Within the milky plastic enclosure lies a compact board comprising of

  • IR Sensor (38KHz)
  • Vibration sensor switch
  • I2C EEPROM (AT24C02S)
  • ABOV MC81F4204
  • CR2032 battery (~3V)

Everything listed is available as a jellybean part except for the very unusual MC81F4204,

The ABOV (MC)81F4204

“8-bit MCU, 4KB Flash, 192B RAM using a custom architecture (“810 Core”)”

Takeaway: difficult to source, ancient proprietary IDE, requires a special programmer

Also: No UART. 192 bytes of RAM

Identifying and buying a good iPhone battery from China

7.57 shipped!

Purchasing a replacement battery for an iPhone (5S) from typical Chinese sources yield fantastic prices, but they rarely match up with their advertised capacity.

What’s in an iPhone battery?

'OEM' battery

Above: What sellers describe as an “OEM” battery. I’ve removed the tape off the battery controller. It is difficult to discern between this and the “Apple Original” battery.

The 2 significant parts of an iPhone battery are:

  1. Lithium Polymer battery (“1S1P”). The remaining capacity of the battery can be approximated by its voltage, at ~3.7V flat, and ~4.2V full. The iPhone 5S has a 1560mAh battery.

  2. The charge controller. This tiny board contains circuitry to protect the board from over-temperature, over-charge and over-discharge, and also reports the battery’s vitals such as its charge state. The 5S board contains the Texas Instrument’s bq27545 and the proprietary flex cable, and is spot welded on the battery’s terminals.