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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.
  1. Heterodyne oscillator
  2. Frequency divider
  3. 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
 

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.  
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