Custom Firmware Unlocks Fitness Tracker

July 3, 2016 by Elliot Williams 17 Comments

[Mikhail] sent us a teaser video for a hack he’d done (embedded below). He takes a Bluetooth LE fitness tracker dongle and reflashes it spit out the raw accelerometer data and trigger events. He then wrote a phone app that receives the data and uses the device as an alarm, an on/off switch, a data-logging device, and more.

We thought it was cool enough that we asked [Mikhail] for more detail, and he delivered in spades! Inside the device is a Nordic NRF51822, their ARM Cortex + Bluetooth chip, an accelerometer, and a bunch of LEDs. [Mikhail] mapped out the programming headers, erased the old flash, and re-filled it with his own code. He even added over-the-air DFU re-flashing capability so that he wouldn’t have to open up the case again.

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Learn Bluetooth Or Die Tryin

February 6, 2016 by Elliot Williams 5 Comments

Implementing a Bluetooth Low Energy (BLE) device from scratch can be a daunting task. If you’re looking for an incredibly detailed walkthrough of developing a BLE project from essentially the ground up, you’ve now got a lot of reading to do: [Jocelyn Masserot] takes you through all the steps using the ARM-Cortex-M0-plus-BLE nRF51822 chip.

The blog does what blogs do: stacks up in reverse-chronological order. So it’s best that you roll on down to the first post at the bottom and start there. [Jocelyn] walks you through everything from setting up the ARM compiler toolchain through building up a linker script, blinking an LED, flashing the chip, and finally to advertising your device to your cell phone. It’s a lot of detail, but if you’re doing something like this yourself, you’re sure to appreciate it.

Of course, all the code is available for you to ~~crib~~ peruse on [Jocelyn]’s GitHub. And for yet more background reading on BLE, check out the Hackaday Dictionary.