Saturday, October 18, 2008


XBee and the USB Interface arrived in the post today.

The USB interface is FTDI based so I'll have to install the driver for MacOSX.


Friday, October 17, 2008


Ordered some 60mw XBee modules and a USB XBee interface from for the Mashroc telemetry project.

I'm going to be building a small PIC based board for the rocket end of
the system and running some tests to check range and
see if there are any doppler related problems.

I did a few quick and dirty doppler calculations which came up with :-

Source f = 2400000000 Hz
Source Velocity vs = 118 m/s (Guessed)
Medium Velocity v = 3000000 m/s (Approximately Light)
Observed fo = 2399905603.71292 Hz
Observed delta do = -94396.2870793343 Hz

I found from a zigbee spec online (must find a better source) the
frequency tolerance is 40ppm which I took to mean 2400*40 = 96 KHz. So
we're just inside the tolerance.
Bear in mind this is worst case doppler with freq source moving directly
away from the observer.

Thursday, October 9, 2008


is running Ubuntu #linux on the lappy. And it's 10^6 times better than that W*ndows crap. And you can still watch #the-owl from #iplayer - bananarama!