Project Delay

Helo Follows, Apologies for the delays. The build team had a little set back where one of the UART pins on the main board got overloaded. This caused a loss of comms to the GPS module. Then One of the build team stupidly went an bought a house, fixing it up became his full time job for a while, but we are back on track to start looking back into the project again soon.
Again, apologies for the delay, we'll go into the UART fix in the next blog, and then soon we hope to start thermal tests.
Ciao, x

Core Flight Components

This is the core of the payload. It is a BeagleBone Black Enhanced(BBE), (made by SanCloud, the really great guys who helped me out with a new board). The board has an internal barometric pressure sensor, temperature and MEMS sensor which measures it's X, Y, Z position and it's acceleration in any direction. All of these sensors will be read as frequently as possible and logged to file so that when the payload is recovered, accurate data about the entire flight can be reconstructed.
The BBE has a Mikroelecronika expansion shield, allowing support for their propitiatory 'click' boards (be careful ordering things from this american company, they don't pay the customs and excise charges the postie will lump those charges on top of your delivery for you). This Click expansion board allows for 4 sub boards to be plugged in.

The purpose of the core flight computer is for payload recovery. There is a GPS module (shown here in slot 2). This module is based around a Quectel L30 chip, a UART controlled device that, when correctly turned on, (turn on three pins, wait, turn on off, wait, stand on one leg and stick your finger in your ear), spews out its GPS location in the form of a NMEA protocol stream.

This stream is parsed and rehashed into UKHAS Habitat protocol, which is then kicked out of the radio (shown here in slot 1). The radio is a Radiometrix NTX2 which was initially designed as an FM radio, but by simply shifting the carrier frequency, an AM radio can be tuned to pick up the two different frequencies as two tones, and transmit RTTY back down to the ground at flight time.

The GSM module (in slot 4) is a Telit GL865-Quad which, when furnished with a SIM card will not only act as an emergency backup location transmitter, but will also be used during flight time to send text messages to a twitter feed to update the world with it's location and a bit of info on how happy it is (or not!)
The last module (Slot 3) is a Dallas 1W Temperature sensor for external measurements.

Here is an exploded view of the entire core flight computer component of the payload. There will be more devices in the payload, such as camera's etc. but this will all be described in another blog post.

Flight/Tracker Details

The flight will be trackable via a downlink from the balloon running at 434.650MHz. An SSB RTTY signal will be transmitted, and can be tracked with an AM or SSB radio. If you have one hooked up to you computer, you can use dl-fldigi to track the flight, see instructions.

Details on the downlink protocol will be attached to this blog post later.

For observers, you will be able to track the flight progress on the tracker website:
https://tracker.habhub.org/
The callsign will be $AJCDX1

History

This has been a very long term project for me. I original had the idea about 7 years ago, but lacked the expertise to build such a device. This project has been through many iterations.
The first project was going to use an Arduino, but only having one UART, I was going to flip between Radio and GSM control using FETs. The stitching caused such spikes on my UART lines that the project was un-workable.

These are the remains of a very early prototype based on a Wavecom data modem. Arduino's had only just started to become popular and it seemed like, as now, people knew there were a good idea but didn't know quite what to do with them. I read an article in new scientist of someone launching a HAB and I was captured by the dream. As a kid I always wanted to be an astronaut, but thus dreams being very much behind me, this seemed like as close to space as I would ever get.

 I ran into some fairly unpleasant voltage level converter problems, that could only be solved with some ridiculously undersized components.
(this little blighter converted 3v3 logic levels to 1v6. This work was all done without the use of a microscope!)

I went through quite a lot of Arduino based solutions, but never managed to get off the ground.
(Yes thats a Minidisc charger in the background. Thats how long ago this was!)

The second generation used an Raspberry Pi, and an old radio that needed PWM RTTY. The Raspberry Pi was not accurate enough to PWM at the rate I needed, so I was going to interface to an Arduino, to do the bit bashing, and the Pi to be the main flight computer. But my ability to program the Arduino tripped me up as a complicated interrupt driven system was required.

I began to once again develop Arduino only solutions, I actually got through about 12 circuit spins as I started to learn more and add more and more features to the project. Here is a picture of one I made with an SD card, before there were any libraries to drive an external SD card, I had to write my own, and ended up creating my own basic filing system!

I still lacked the expertise in software to bring all the individual parts together.

Given enough time, I evenually learned how to program multi threaded code. This would be the key I needed to crack the software side of things. Finally, I found the BeagleBone. The cloud9 development system on it is so easy to get started on, and due to a recent hardware enhancement, some of the sensors I wanted were already on the board. A little help from the guys at SanCloud are enabling me to achieve this very long term plan.