Vectorplot

Since I don't own a vector analyzer, I've been working on a software implementation for the RTL SDR in flat C (using libusb1) and X11 so I can test my FPGA QAM code. It actually turned out to be much simpler than expected, and is working well thus far.



Right now it plots raw I and Q values on the plane as well as calculated FFT data. Since I haven't implemented clock recovery yet, signals appear as a circle (recall that for a frequency difference of N hz between the incoming signal and the sampling frequency, an N hz rotation around the IQ plane results - thus even a difference of a few hz is too quick to see anything but a circle). That shouldn't be very hard, and at that point it will become fully usable as a vector analyzer.

Code is here: https://github.com/jackcarrozzo/vectorplot.