In this quick little demo i will show you real time 256 point audio band spectrum analyzer, i will be using ezdsp5502 board , which has TMS320VC5502 and for input signal sampling we are using onboard audio codec TLV320AIC3204B to sample input signal at 48Khz sampling rate. its post is not going to be tutorial for FFT , the scope of this post is only to show how to get contentious input sampling ,FFT calculation and display on the little FFT Display.
i have used ezdsp board and onboard codec, there was no extra hardware required. ezdsp schematic available online. i am using my MDO3000 Arbgen to generate test signals. at around 2Vpp.
There is no magic in the firmware, i am setting up mcbsp in i2s mode , and initialize TLV320AIC3204 as I2S master , which give interrupt on every I2S word reception , i put all samples into buffer. and as buffer fills up , i calculate 256 point in place FFT , after this i calculate absolute value for each FFT point output. then plot the output to the OLED screen.