RE: Interfacing ADS1298 and nRF52840 via SPI

gauthamranganathan — Mon, 24 Dec 2018 06:15:25 GMT

Turbo J Thanks a lot for your suggestions.

RE: Interfacing ADS1298 and nRF52840 via SPI

Turbo J — Sat, 22 Dec 2018 13:08:35 GMT

Re-read the datasheet of the TI ADS1298. The maximum supported SPI clock is 10MHz.

There is an additional required ADC clock of 2 MHz, but the chip can generate this signal internally.

Running the chip at full 32000 Hz sampling rate requires 8 MHz SPI bus frequency when using the NRF SPIM peripherial (28 byte/sample * 8 bits/byte * 32kHz = 7,168,000 Hz). But the data quality is significantly reduced at high sampling rates - much more noise is present.

I suggest using the chip at its default 500 Hz or 1000 Hz for standard ECG applications, because there will be a lot less noise in the ADC data and you can use lower SPI frequencies.

When using softdevice, you might want to trigger the SPI transaction using GPIOTE input via PPI channel.