We're planning to use an AD7609 in our designs, so we got an evaluation board and hooked it up to the SPI controller.
Looking at the Linux IIO drivers, the AD7609 is a close match to the AD7606 family, only it's 18-bit instead of 16.
The way to go here seems like adding support for the 7609 in the ad7606*.c driver. I'm uncertain though as how to handle the 18-bit format. The hardware just outputs a "packed" 18 bytes of data for 8 channels at 18-bit. I could decode this in the driver and expand to say 32-bit per sample with only 18-bit significant data, or I could leave this up to user-space. The latter seems the more versatile choice.
We'll be feeding a constant (5 kHz) clock to the "start conversion" pins.
Any advice or futher hints on this?