Friday 13 May 2011

The BlueFlyVario concept

In order to control myself, and stop heading off on a tangent, I gave myself a limited goal. Make a working bluetooth pressure sensor prototype device that can be used with an Android app to provide basic vario functionally.

The features of the device would be:
  • Low cost, ideally less than $US50 in components per device for the production of ten prototypes. 
  • Simple electronics with the bare minimum of components:
    • A digital pressure sensor module - easy to interface with a micro controller with I2C or SPI interface.
    • A micro controller IC - cheap, must have free C compiler available and offer lots of ports.
    • A bluetooth transmitter module that uses the Simple Port Protocol for easy access on the target device.
    • Voltage regulator IC - something efficient and not electrically noisy.
    • LiPo battery, ideally one from a mobile phone so it is easy to source. I want to be able to use the device for at least 20 hours without recharging.
    • Recharge circuitry that allows recharge from a USB port.
    • Surface mount resistors and capacitors.
    • Small circuit board.
    • Case, ideally starting with an existing case design
    • A few LED's for indicating connection status
    • One button (on/off)
  • It should spit out pressure data often enough to enable an Android vario app at least as capable as commercial varios.
The Android bluetooth app would have the functionality of basic varios that are available on the market today. This would include a visual vertical speed indicator and an averager, a few user settable altimeters, etc.

I wanted this device and app not just for me, but for the broader flying community. This means that I planned to do the following:
  • Provide this blog, so other pilots could get their geek on.
  • Make the vario software open source with something like the LGPL licence, so anyone could copy it and use it for anything. I do not intend to sell the app, it will be free. 
  • Make the bluetooth data stream format open so that other developers can make apps, either using my basic vario app as a reference or make their own app.
  • Provide enough info so others could replicate the hardware development. However, I intend to produce the bluetooth devices in limited quantities and sell them for less than $100 each, enough to cover costs of components and production.
I am calling my thingy the BlueFlyVario. Why? Well, I am not really good at choosing names.