I am working on device which receive and demodulate FM signal, then audio samples are going through FPGA to perform some realtime DSP on it, after this I want to modulate and transmit audio back again using other FM frequency.
I modified custom HDL design to bypass audio output. Now I have signal after DSP on both zedboard audio outputs and 48kHz samples on AXI register to which I have easy access from Linux running on zedboard.
Is there any easy way to FM transmit data from AXI register?
I tried transmission directly from audio drivers(It's easy to make that kind of audio source in gnu-radio). I connected output and input by jack cable but it resulted huge delays. There was no way to make audio playback using software. I tried to make virtual sound cards, modify settings in pavucontrol, JACK(tons of errors using it) etc.
Also I tried to modify that method: Simple FM transmitter using gnuradio - Opendigitalradio but there were much bigger delays and corrupted signal.
Next idea was to modify "AD9361_iiostream.c" file, but I am not sure how to prepare audio samples to send. I got repeated silent breaks in transmitted signal.
Btw. Each time I received signal and transmitted something at the same moment, I got overruns and underruns while moving the cursor or open some other apps.