ARM Cortex-M3 (STM32F103) Project - 32 Point DFT Audio Spectrum Analyzer

In this project, I made an audio spectrum analyzer project using ARM Cortex-M3 (STM32F013C8) and LCD 16x2. This project is the application of the real DFT algorithm from my previous post. I used 32 point real DFT for this project. 32 point DFT will transform 32 samples of time domain signal to 17 point frequency domain signal. The first point of frequency domain signal is DC. I will only display AC part (16 point) of frequency domain signal, which is from index 1 to 17 into 16 columns of LCD 16x2.

My audio sampling rate is 35.15kHz. So, the maximum frequency domain signals that can be displayed is up to 17.5kHz (Nyquist's theorem) and the resolution is 17.5kHz/16≈1kHz.

The circuit for this project is same with the circuit for my simple audio effect project. The only differences is the LCD 16x2 and there is no dip switch circuit. You can see the detail about this circuit on this post. For the LCD, I used the custom character feature to create 8 type of bar graph. If you want to learn how to create custom char on LCD 16x2, you can see this tutorial.

ARM Cortex-M3 (STM32F103) Project - DSP Audio Effect

In this project, I made a simple real-time DSP (Digital Signal Processing) project using ARM Cortex-M3 (STM32F013C8). The signal processed in this project is audio signal that come from electronic devices through 3.5mm audio jack. The audio signal is processed using STM32F103C8 microcontroller.

There are 3 simple audio effect that implemented in this project. These effects are low pass filter, pitch up, and pitch down. The audio output from this microcontroller is sent to an active speaker. This is block diagram of this system: