A simple spectrum analyzer using dsPIC30F4011

This is a project for viewing the frequency spectrum of input signal using dsPIC. The hardware uses the following: –

1. dsPIC30F4011.
2. Opamp (any one, like LM358, TL084).
3. Power supply.
Software includes the following: –
1. FFT library code from Microchip

2. Graphic LCD driver code (for line, pixel plot etc).

Graphic LCD showing spectrum of a square wave: –

Description of hardware: –

The dsPIC runs on the internal oscillator of 7.37MHz, which is then raised close to 30MHz using the PLL. This enables the board to run without external oscillators and associated loading capacitors.

Spectrum Analyzer
The signal to be analyzed is passed through a high impedance resistor (1Mohms) and then amplified by opamp (TL084). This is done to avoid any high voltage damaging the dsPIC or associated circuit. DC offset is added to the signal to enable it to be measured by ADC (0V to 5V).

A programmable gain amplifier (MCP6S21) is used to scale the signals through software. Otherwise, we had to provide a potentiometer to select different gain. The signal is then fed into analog channel of dsPIC.


For more detail: A simple spectrum analyzer using dsPIC30F4011

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