Spectrum analyser runs off a coin-cell battery
A Dorset-based designer has combined a Texas Instruments MSP430 microcontroller with a Sharp Memory LCD to make a credit-card sized audio spectrum analyser that can run off a coin-cell battery.
It can display an fast Fourier transform (FFT) result using less than 10?W.
“Static current for the board is under 3?A with the display and RTC active. Current is around 1.5mA whilst sampling and number-crunching and we got a 50dB SFDR from a line-level input,” said Robert Hancox, founder of Bridport-based RHDC Services.
“We created the FFTD1A development board as a prototyping platform for ultra low power designs,” said Hancox.
The original intention was to use it for a handheld product design. “But we soon found other uses and in a spare moment we used one to make a real-time audio spectrum analyser,” said Hancox.
The fast Fourier transform code was generated using a software tool called FFT Designer.
For its signal acquisition stage the analyser uses the internal analogue-to-digital converter of a MSP430 microcontroller and a 256 point FFT with Kaiser windowing function for the actual spectrum analysis.