Wednesday, March 14, 2012

Freetronics MobSenDat: The rocketses tail.

I was fortunate enough to get my hands on a MobSenDat board which was on offer at the Arduino mini conf at LCA 2011. Being a software guy, soldering hardware is a traditional weak point for me, so I decided to construct a $30 Freetronics KitTen board first. Seemed like a good idea since these boards are cheaper and much more readily available in case of a dead starter construction.

Like many, I was overjoyed to see my flashing LED between the GRD and PIN 13 on the KitTen! So with the little courage boost I started on the MobSenDat board. After a few sessions slowly moving along there, and a little defluxing at the end, I got to a stage that I thought the board was "OK".

As you can see, I've not got the ZigBee love happening yet. But put the NTX2 antenna point on the board just for fun ;) It seems the go is to get a zigbee to usb for lappy or tablet usage and two zigbee pro chips to get a radio link up and running:

Having tinkered in the arduino IDE for the kitten, I wanted to get the software up and ready in some state to upload to the mobsendat. The repo I grabbed from after a bit of sifting was this one:
Another repo tucked away for later is this one:

So with library setups I got the IDE to compile the code for the Pro8mhz/ATmega328P chip. After a little ginning around I uploaded that over the cable to the mobsendat. Slightly different to the kitten as there are no resets on the mobsen and it boots right off an external 9v battery.

Opening the serial console gave me the first worrying moment. Some stuff appeared on a regular basis but it was non ascii garbage. Changing the baud rate to 38k and some more expected text appeared! Times, temps, pressures, x,y,z readings...

A huge thank you to Luke Weston and the Freetronics guys for making these things available, and robust enough that even somebody with limited soldering skill can construct them.

In the process I also sniffed out the mobsendat2 board for those who are interested in these sorts of things:

I might end up using the kitten as a parachute deployment board or for other flight instrumentation. My next build will be larger and probably based on a 54mm motor mount tube. Now that I have working electronics I want an electronics bay in the build...

No comments: