Thursday 21 March 2013

Experimenters Version

I am toying with an experimenters version of the BlueFlyVario. I got a batch of circuit boards made, but have only populated one for my own use. The idea is to expose all of the spare micro-controller pins so daughter boards can be designed to provide additionally functionality. Additionally, the In Circuit Serial Programming (ICSP) pins have been exposed to allow easy reprogramming of the micro-controller using a PICKIT 2 or equivalent programmer. A picture of the board design is shown below. The pins are exposed in a 0.1" series of through holes to allow standard headers. It is possible to still put the board in the DP5031 case I used for prototype version 5 (and intend to use in version 6).

Up until now I have used software SPI (bit banging) for the interface between the PIC24F16KA101 and the MS5611 pressure sensor. In this experimenters version I have moved the interface to the hardware SPI pins on the micro-controller. This has meant a pretty significant change to the firmware. It also means that adding additional devices to the SPI bus becomes less of a hassle.

The exposed pins will allow additional (spare) PIC24F hardware features to be used; including an AD channel, UART, I2C, and general IO pins. I will be using the experimenters version to get the code right for prototype version 6 (which is just the same as version 5 to look at, but will be easier to make and is electronically much more similar to this experimenters version). I have lots of ideas for daughter boards and altered firmware. These are all independent ideas, I am not thinking of doing them all in the one device!:

  • Two additional pressure sensors configured in such a way that allows connection of pitot and static tubes.
  • An LCD screen display (I have pretty much got a Nokia 84 x 48 LCD screen working already on a breadboard)
  • A small ePaper display (something like this; or without the arduino integration overhead
  • Integrating two high resolution 1D accelerometers. These would be physically connected to each riser. The idea is to see if I can measure the 'feeling' of wing feedback we get to improve the flight instrument. 
  • Integrating an ISM RF transceiver to transmit the vario data over ranges up to a few km. 
  • Integrating a GPS receiver to get better data than what a phone spits out.
  • Integrating a speaker to develop the code for audio output.

I still expect that the standard version 6 hardware will be what most people will want. I am intending to get quite a few of them made. The experimenters version 6a will be available in much more limited quantities for those that fell they have the electronic design skills to make use of it. My aim is to release both by the end of April with firmware code and updated schematics.