I've successfully designed and assembled my digital stack board over the past two weeks, featuring an STM32F407VET6 microcontroller paired for the ADS1299  breakout board . The hardware looks solid and the STM32 handles USB data transmission to the host computer well. My firmware is mostly complete and works perfectly up to 4kSPS sampling rates, but I'm running into SPI communication errors when pushing toward the full 16kSPS capability of the ADS1299. There's no particular reason I need the maximum sampling rate, but it seems worth implementing since the hardware supports it.  I'm using gold cup electrodes with Ten20 conductive paste and NuPrep for skin preparation, and I'll be diving into proper electrode placement techniques next.