MSP430 bat detector

This is my first proper project using the MSP430

Started 12th May 2008.

Aim

Create a low power hand held bat detector.

Approach

I've never built, or used, a bat detector before, but searching the web suggests there are 3 methods for listening to the echo location calls of bats.

Heterodyne oscillator
Frequency divider
Digital recording (and slow replay)

All three methods seem realistic using the MSP430 and a small number of extra components. Each technique also creates further opportunities for more projects in areas such as software defined radio (SDR), data logging, and electronic music. The digital recording approach seems to be the more challenging, and if successful will create a tool that doesn't already exist.

Resources

http://a-s.clayton.edu/burnett/research/default.html (recording and analysis using laptop, MatLab, etc)
http://pw1.netcom.com/~t-rex/BatDetector.html (the "simple bat detector". Frequency divider) Featured in Make.
http://www.btinternet.com/~mr.pentops/bat.htm (heterodyne detector built from modified transistor radio)

Hardware

The prototype is based on a EZ430-T2012 module.

Pins

IC pin	name	role
1	VCC	-
2	P1.0	LED
3	P1.1/A1/TA0	ADC in
4	P1.2/TA1	PWM out
5	P1.3	button
6	P1.4	SD flash
7	P1.5	SD flash
8	P1.6	SD flash
9	P1.7	SD flash
10	RST	program
11	TEST	program
12	XOUT	xtal
13	XIN	xtal
14	GND	-

Software

Reading/writing SD flash

Reading any size block, starting at any point, is allowed. Writes must be in 512 byte blocks at 512 byte boundaries. This, plus the low available RAM, implies that some waste of SD flash storage may occur. The most efficient use of resources is most likely to write data as it is acquired and use RAM to buffer reads (since playback will be at lower speeds, less data is needed). If playback is at 16th speed for each 512 bytes written, 32 will need to be read.

Pulse width modulation (PWM) audio

The duty cycle is set through the CCR1 register.

self-aware