So far, so good (and Thank you Pavel, your Alexiares protocol integration seems to run "nice and easy")
The red pitaya and your firmware help me a lot debugging (and understanding) the way filters, antenna outputs, attenuators and preamp are switched using the SPI

I'm waiting for the filter boards, HPF and LPF (Gerber have just been send last week to a Chinese pcb manufacturer)
I will try to test the I2C implementation this afternoon...