Maxim Integrated MAX32664C, Quick Start Manual, Page: 17 / 24

Maxim Integrated Page 17 of 24
3 Measuring Heart-Rate on Wrist (WHRM)
3.1 Setup
A typical heart-rate sensing design has two PDs that are located at the same distance from green
LED. In this case, PPG signal from both PDs can be used for WHRM calculation.
For other type of PD setups, set the PD configuration from the host accordingly using the
commands provided in Table 15 prior to enabling the algorithm.
3.2 Raw Data Collection Mode
For hardware testing purposes, the user may choose to start the MAX32664C to collect raw PPG
samples. There are two ways to accomplish this, which are detailed as follows.
3.2.1 Raw Data Collection in Algorithm Mode
In Algorithm mode, automatic exposure control (AEC) and skin contact detection (SCD) may be
turned off to collect raw PPG data (steps 1.1 and 1.2 in
Table 10
). In this case, LED currents will
not be adjusted automatically; the heart-rate measurement algorithm may not converge and
should be discarded. Although the algorithm is running, it will not affect the PPG samples. If the
reported PPG data is saturated, you can reduce the LED currents. Note that updating the
MAX86141 registers should occur AFTER enabling the algorithm and the MAX86141, or they will
be overwritten during initialization.