AFE4400

The AFE4400 is a pulse oximetry analog front-end chip by TI. It controls LED switching, has ambient light cancellation, and other very nice features for pulse oximetry applications.

The main communication interface for the AFE4400 is via SPI. However, there are also some digital pins that can be configured for smoother operation; two are required and four are for additional diagnostic value.

Mandatory

• adc_pdn: The powerdown pin; should be held high (not floating!) for the duration of operation.
• adc_rdy: The "ADC Ready" pin, indicating a sample is ready for reading. It is useful to use adc_rdy as the driver for an edge-triggered interrupt.

Optional

• daig_end: Diagnostics complete
• adc_done: ADC conversion complete
• led_err: Connection issue with the LEDs
• sensor_err: Connection issue with the photodiodes