With apologies if this is the wrong place to put this... but does anyone have any experience building such an animal? The search engine produces a few references, but nothing helpful, and while google produces a lot of good information, there's little recent or directly equivalent.
It's essentially an integrating altimeter which logs and displays altitude (referenced to take-off, mean sea level, or a reference sea level pressure) and also indicates short term (1/4 second) and average (30 second) changes in altitude. This latter option is accompanied by an audible warning; beeps or continuous tone indicating lifting and falling and the frequency of the tone indicating the rate of change.
As a bonus, USB connection to a PC should allow the copying of logged data, and of course, it should do all this in a minimum weight, minimum power sort of way :)
My first tentative sketches suggest something along the lines of the motorola MPX4115 pressure sensor which produces a temperature compensated linear 0.6v-4.6v output; some analogue processing to amplify, filter, and shift the output Ievel to 0-5v for the ADV input (for better noise/range) followed by oversampling to improve the dynamic range.
Conversion of pressure to height probably via a look-up table; a real-time clock on TWI, a nice fat serial eeprom for the logging data, and a piezo sounder.
Display on a serial LCD - the Lascar SP 5-GFX1 looks rather good - and either a joystick switch or a rotary/push coder to control it. USB from the FTDI 245 which looks rather interesting and reasonably inexpensive, and an M32 to tie it all together.
The expensive bit is likely to be the pressure sensor, but this should all go together for under fifty quid for a proto, I think.
p.s. I'm a paraglider pilot, in case you were wondering.