Pushing a AD7476 on a pHAT looks promising. 12 bits, 1Msps, let's see !

Testing with a SPI_CLK at 1MHz, with a 1khz beacon, getting 9.5khz from the ADC:

Humm.. not the speed I'd be expecting. Let's explore the speed of sampling (Fech, in orange) vs the speed of the SPI_CLK (in blue). Seems it's stuck at 10khz for the RPi:

That would come from the RPi SPI overheads, with large intervals between captures. The below has a SPI_CLK at 18MHz, with large overheads between words:

Now: just need to find out where to accelerate the spi =)