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Maxim Integrated MAX32664C Quick Start Manual

Measuring spo2 and heart rate
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Measuring SpO
and Heart Rate
2
Using MAX32664C – A Quick Start Guide
UG6924; Rev 0; 6/19
Abstract
The MAX32664C is a variant of the MAX32664 sensor-hub family, which is specifically targeted
for measurement of SpO
and heart rate. Combined with the MAX86141 optical sensor and a 3-
2
axis accelerometer, it provides the sensor's raw data, as well as calculated SpO
or heart-rate
2
data, to a host device through its I
2
C slave interface. This document provides step-by-step
instructions that enable a user to communicate with the MAX32664C and to calibrate, configure,
and receive measurement and monitoring data.
Maxim Integrated
Page 1 of 24

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Summary of Contents for Maxim Integrated MAX32664C

  • Page 1 Using MAX32664C – A Quick Start Guide UG6924; Rev 0; 6/19 Abstract The MAX32664C is a variant of the MAX32664 sensor-hub family, which is specifically targeted for measurement of SpO and heart rate. Combined with the MAX86141 optical sensor and a 3- axis accelerometer, it provides the sensor’s raw data, as well as calculated SpO...

  • Page 2: Table Of Contents

    Table of Contents Introduction ........................... 4 1 Architecture ..........................5 1.1 Communicating with MAX32664C ..................6 1.2 Accelerometer ........................7 2 Measuring SpO 2 on Wrist (WSpO 2 ) ..................8 2.1 Initial Calibration Mode for Final Product ................8 2.2 Raw Data Collection Mode ....................
  • Page 3 List of Tables Table 1. Read Status Byte Value ....................6 Table 2. Host-Side Accelerometer—Sending Data to MAX32664C ..........7 Table 3. Host Commands—WSpO 2 in Calibration Mode ............. 9 Table 4. Format of Received Samples—WSpO 2 in Calibration/Algorithm Mode ....... 10 Table 5.

  • Page 4: Introduction

    Introduction The MAX32664C is a variant of the MAX32664 sensor-hub family that enables users to capture raw data, as well as calculated SpO and heart-rate data. The part is preprogrammed with the firmware, drivers, and algorithm that are required to interface with the MAX86141 sensor device through the SPI port.

  • Page 5: Architecture

    MAX86141 optical sensor through the SPI bus. An accelerometer is mandatory for heart-rate monitoring. A KX122 accelerometer can be connected directly to the MAX32664C. Alternatively, an external 3-axis host-side accelerometer can be used. In this case, the host needs to periodically provide accelerometer readings to sensor- hub using the commands provided in this document.

  • Page 6: Communicating With Max32664C

    1.1 Communicating with MAX32664C A host should use the I C bus to communicate with the MAX32664C (slave) using a series of commands. A generic write command includes the following fields: Slave_WriteAddress(1 byte)|Command_Family(1 byte)|Command_Index(1 byte)|Value(multiple bytes) A generic response includes the following fields: Slave_ReadAddress(1 byte)|Status(1 byte)|Value (multiple bytes) Slave_WriteAddress and Slave_ReadAddress are set to 0xAA and 0xAB, respectively.

  • Page 7: Accelerometer

    Otherwise, the reported heart rate will not be correct during movement. A sensor hub accelerometer can be integrated through the SPI port of the MAX32664C. In this case, the required driver for KX122 is already included. The user only needs to follow the reference schematics to connect the accelerometer and enable it before starting the algorithm, as described later in this document.

  • Page 8: Measuring Spo 2 On Wrist (Wspo 2 )

    Guidelines for SpO2 Measurement Using the Maxim MAX32664 Sensor Hub application note. Once three calibrations coefficients are obtained, they need to be loaded to the MAX32664C every time prior to starting the algorithm. But first, they are required to be converted to 32-bit...

  • Page 9: Table 3. Host Commands-Wspo 2 In Calibration Mode

    Calibration Mode RESPONSE HOST COMMAND (HEX) COMMAND DESCRIPTION (HEX) Host initializes MAX32664C in calibration mode and starts algorithm using following commands: AA 10 00 03 Set output mode to sensor + algorithm data AB 00 (streamed data will include PPG, accelerometer, and algorithm data.

  • Page 10: Table 4. Format Of Received Samples-Wspo 2 In Calibration/Algorithm Mode

    Low SNR Algorithm Shows low SNR in measurement flag (9 Bytes) Motion flag Shows excessive motion Reported status of algorithm: LED adjustment: 0 Status Computation: 1 Success: 2 Timeout: 3 Maxim Integrated Page 10 of 24...

  • Page 11: Raw Data Collection Mode

    2.2 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. 2.2.1 Raw Data Collection in Algorithm Mode In Algorithm mode, AGC may be turned off to collect raw PPG data, as seen in the first step in Table 5.
  • Page 12 Disable AFE (e.g., MAX86141).* AB 00 AA 44 04* 00 Disable accelerometer.* AB 00 AA 52 05 00 Disable WSpO algorithm. AB 00 *Provided indexes are examples for sensors such as the MAX86141 AFE or KX122 accelerometer. Maxim Integrated Page 12 of 24...

  • Page 13: Pure Raw Data Collection

    2.2.2 Pure Raw Data Collection The host can configure the MAX32664C to work in Raw-Only mode (no algorithm). Table 6 lists the set of commands that are needed to work in this mode. In this case, only LED counters and accelerometer data will be included in the received samples.

  • Page 14: Table 7. Format Of Received Samples-Wspo 2 In Pure Raw Mode

    PPG Data LED4 Red LED counter (18 Bytes) LED5 IR LED counter LED6 accelX Two's complement. LSB = 0.001g Accelerometer accelY Two's complement. LSB = 0.001g (6 Bytes) accelZ Two's complement. LSB = 0.001g Maxim Integrated Page 14 of 24...

  • Page 15: Algorithm Mode

    BEFORE enabling algorithm. AA 52 05 01 Enable WSpO algorithm. AB 00 Host reads samples upon receiving MFIO interrupt by MAX32664C (repeated as needed): AA 00 00 Read sensor hub status byte: AB 00 08 Bit 0: Sensor comm error...

  • Page 16: Algorithm Settings And Configurations

    AGC timeout in seconds 0x07 0x1E (8-bit unsigned) 0x08 WSpO algorithm timeout in seconds 0x78 Configure the source of the PPG signal for the photo detector (PD) 0x09 0x02 0x01: PD1 only 0x02: PD2 only Maxim Integrated Page 16 of 24...

  • Page 17: Measuring Heart-Rate On Wrist (Whrm)

    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.

  • Page 18: Table 10. Host Commands-Whrm Raw Data With Algorithm Mode

    HOST COMMAND RESPONSE COMMAND DESCRIPTION (HEX) (HEX) Host initializes the MAX32664C in Algorithm mode with AEC and SCD off and starts algorithm using the following commands: AA 50 02 0B 00 Turn off algorithm AEC. AB 00 AA 50 02 0C 00 Turn off algorithm SCD.

  • Page 19: Table 11. Format Of Received Samples-Whrm In Algorithm Mode

    10x heart rate Confidence Calculated confidence in % 10x RR - inter-beat interval in ms WHRM Activity class: Algorithm Rest: 0 (6 Bytes) Other: 1 Activity Walk: 2 class Run: 3 Bike: 4 Rhythmic: 5 Maxim Integrated Page 19 of 24...

  • Page 20: Pure Raw Data Collection

    3.2.2 Pure Raw Data Collection The host can configure the MAX32664C to work in Raw-Only mode (no algorithm). Table 12 lists the set of commands that are needed to work in this mode. In this case, only the LED counters and accelerometer data will be included in the received samples.

  • Page 21: Table 13. Format Of Received Samples-Whrm In Pure Raw Data Mode

    Green 1 counter LED2 LED3 MAX86141 (18 Bytes) LED4 Green 2 counter LED5 LED6 accelX Two's complement. LSB = 0.001g Accelerometer accelY Two's complement. LSB = 0.001g (6 Bytes) accelZ Two's complement. LSB = 0.001g Maxim Integrated Page 21 of 24...

  • Page 22: Algorithm Mode

    HOST COMMAND RESPONSE COMMAND DESCRIPTION (HEX) (HEX) Host initializes the MAX32664C in Algorithm mode and starts algorithm using the following commands: AA 10 00 03 Set output mode to sensor + algorithm data. AB 00 AA 10 01 05 Set sensor hub interrupt threshold.

  • Page 23: Algorithm Settings And Configurations

    0.1g. (16-bit unsigned) read Minimum PD current in 0.1mA. 0x10 0x001E (16-bit unsigned) Configure the source of the PPG signal for the PD. 0x11 0x01: PD1 only 0x01 0x02: PD2 only 0x03: Both PD1 and PD2 Maxim Integrated Page 23 of 24...

  • Page 24: Revision History

    Initial release — ©2019 by Maxim Integrated Products, Inc. All rights reserved. Information in this publication concerning the devices, applications, or technology described is intended to suggest possible uses and may be superseded. MAXIM INTEGRATED PRODUCTS, INC. DOES NOT ASSUME LIABILITY FOR OR PROVIDE A REPRESENTATION OF ACCURACY OF THE INFORMATION, DEVICES, OR TECHNOLOGY DESCRIBED IN THIS DOCUMENT.

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