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In all the examples, the cpu is running at 64 MHz and the peripherial bus at 32 MHz. This means that one timer can drive several output compare units for waveform generation, or act as a time reference for several input compare units. PIC architecture separates timers, from compare units and from input capture. This means that you need the pt_cornell.h file described below. Timers, Output Compare, PWM, and Input CaptureĪll of the following examples use Protothreads.The following images give the matlab comparison of exact and approximate log for noise, and a sinewave FFT on the PIC32. Evaluation of the algorithm as a matlab program is here. (Generation of Products and Quotients Using Approximate Binary Logarithms for Digital Filtering Applications, IEEE Transactions on Computers 1970 vol.19 Issue No.02) gives more resolution at lower amplitudes( code). Taking the log of the magnitude using a fast approximation This approximation is accurate within about 4%. The magnitude of the FFT is approximated as |amplitude|=max(|Re|,|Im|)+0.4*min(|Re|,|Im|). There is some aliasing of the square wave so the peaks are not clean, but you can see the 1/f spectrum. The two images show a sine signal and a square wave captured at 900,000 samples/sec.
#Creating a sine wave in mplab xc8 free#
Running the compiler at optimization level 1 (highest free compiler level) reduces the number of cpu cycles to 146,000, or about 2.4 milliseconds for Hanning-FFT-magnutude calculation. If we include the time to Hanning window the signal and compute the magnitude of the complex output, the process takes 454,800 cpu cycles (with no optimization), or about 7.6 milliseconds. A 512 point complex FFT takes 410,000 cpu cycles (with no optimization) or about 6.8 milliseconds.
#Creating a sine wave in mplab xc8 tv#
The TV framework described below was used as a spectrum analyser by adding a fixed point FFT routine. See links at the end of this page.Īlso refer to Tahmid's Blog for other experiments on the PIC32.ĭiscussions with Syed Tahmid Mahbub have been essential for my learning to use the PIC32. The general way to learn this processor is to look at examples which come with the MPLAB distrubution, Use the MPLAB help to understand the plib syntax, Use the MCU datasheet to figure out the size and meaning of the data field in each control register, then use plib.h, or the header files it includes, to get the actual values of the constants used in the examples for each data field.
![creating a sine wave in mplab xc8 creating a sine wave in mplab xc8](https://static-assets.imageservice.cloud/4877675/microcontroller-top-talks-in-february-on-edaboardcom-forums.png)
This is a start at understanding how the chip works. The intention is to introduce PIC32 into ece4760 in the Fall 2015 semester.