EEG circuit with ADS1299. Help on schematic, SSI comms and PCB layout

Hello everyone!

I am a robotics engineer based in London and I have interest in sensing and electronics. As a part of a personal project, I want to design my own EEG setup (potentially to control a robot). I stumbled open work done by other people/companies, and the ADC of choice seems to be the ADS1299 from Texas Instrument.

I have a lot of experience with analog PCBs (I design PCBs for guitar amps), however I never had the chance to do SMD boards for sensing: I figured this would be a great learning experience :)

I have created my schematics and layouts in Eagle and the board is basically completed. I would love to have some expert opinion o the results, and any suggestions you might have that might increase the chances of success :)

A couple of things to note/doubts:

- I'm using a 2 layers PCB

- ground planes and fence vias on both sides

- I'm using an external oscillator for the clock: not sure the location of it on the board is best to avoid noise/interference

- I tried to separate the analog and digital signals, not sure if this is the best practice

- I'll be using SPI communication with a Raspberry PI (never used SPI before, so I hope the wiring is correct)

- I kept the supply and filtering components quite far from the chip and the digital signals as much as possible

Please let me know your thoughts, hope to learn more about circuit design and add some knowledge to my toolbox :)

Hi-res schematic here: