System Board 6657

MAXREFDES220#: Finger Heart Rate and Pulse Oximeter Smart Sensor with Digital Signal Processing

The MAXREFDES220# reference design provides everything you need to quickly prototype your product to measure finger-based heart rate, blood oxygen saturation level (SpO2), and blood pressure trending (BPT).

The MAX30101 and the MAX32664 provide an integrated hardware and software solution for multiple finger-based applications. The MAX32664 firmware provides algorithm output.

A MAX32630FTHR is provided to emulate a host system for easy development.

Design files, firmware, and software can be found on the Design Resources tab. The board is also available for purchase.


  • MAX30101 Heart Rate Monitor and Pulse Oximeter
    • Tiny, 5.6mm × 3.3mm × 1.55mm 14-Pin Optical Module
    • Integrated Cover Glass for Optimal, Robust Performance
    • Ultra-Low Power Operation for Mobile Devices (<1mW)
    • Programmable Sample Rate and LED Current for Power Savings
    • High SNR (Signal-to-Noise) Ratio, >80dB (typ)
  • MAX32664 Sensor Hub
    • Maxim-Licensed Firmware for Complete Algorithmic Support of: 1) Finger Heart-Rate and Blood Oxygen Saturation Calculations or 2) BPT, Heart-Rate, and Blood Oxygen Saturation Calculations
    • Industry-Standard I2C Interface for Communication with Host Controller
    • Dedicated Bootloader Authenticates Secure Firmware Updates
  • 3-Axis Accelerometer
    • Provides Greater Accuracy
    • Compensates for Motion Artifacts
MAXREFDES220# System Board Enlarge+


The MAXREFDES220# provides detailed design information for using Maxim devices to quickly implement the measurement of heart rate, SpO2, and BPT using reflective photoplethysmography (PPG).

The MAX30101 operates from a 1.8V power supply and a separate 5.0V power supply for the internal LED. Many device parameters are configurable using the MAX32644. The module can be shut down through software with zero standby current, allowing the power rails to remain powered at all times.

MAXREFDES220# System Board Enlarge+

The MAX32664 is a small, low-cost, power-optimized sensor hub for finger-based applications using the MAX30101. The hub collects and processes the output of the PPG and accelerometer transparently through a dedicated I2C interface. A second, standard-mode I2C interface connects to the host through a dedicated command set. The MAX32664A version is for heart rate and SpO2, whereas the MAX32664D version is a superset of the MAX32664A with an added BPT feature. The MAXREFDES220# can be programmed to accommodate either of the versions.

A Windows®-based GUI configures the sensors and graphically displays raw and processed heart-rate and SpO2 data. It also provides the ability to collect and log sensor output for offline evaluation. The MAXREFDES220# may also be reprogrammed with the BPT, heart rate, and SpO2 firmware, and an Android app is used to display those results.

The included MAX32630FTHR board emulates a host system for easy development. Source code for the MAX32630FTHR firmware is available on the Arm® Mbed site to allow customers to implement their own custom host on any platform.

As with all Maxim reference designs, the bill of materials (BOM), schematics, layout files, Gerber files, firmware, and software are all available online.

System Diagram

The MAXREFDES220# reference design block diagram.

Quick Start Guide for Heart-Rate Monitoring (HRM) and SpO2 (MAX32664A Evaluation Software)

Installation Procedure for HRM and SpO2 (MAX32664A)

  1. Assemble and connect the reference design hardware.
  2. Verify the operation of the MAX32630FTHR host by observing the LED on the MAX32630FTHR immediately after connecting the USB cable.
    • If the LED briefly turns yellow, and then blinks green, the MAX32630FTHR is programmed correctly and ready for use.
    • If the LED blinks yellow, then the MAX62630FTHR has been initialized but the sensor board is not responding. Unplug the USB cable. Separate and reconnect the sensor board and MAX32630FTHR, and then connect the USB cable again. If the condition persists, contact Maxim technical support for assistance.
    • If the LED turns red or blinks any other pattern or does not illuminate at all, update the MAX32630FTHR. Important: Both the .bin and the .msbl files must be flashed to the latest version in order to use the latest GUI.
    1. Navigate to the Maxim website and enter MAXREFDES220# into the search tool. Select the entry for MAXREFDES220# in the Product Results section.
    2. On the product Overview page, select the Design Resources tab and download the HRM and SpO2 Eval Package under Software Files.
    3. Extract the downloaded files to a directory such as: c:\maximintegrated\maxrefdes220\hrm
    4. Connect the 10-pin SWD cable between the MAX32630FTHR and the MAX32625PICO.
    5. Connect a USB Micro-B cable to the MAX32625PICO.
    6. Flash the MAX32630 firmware (.bin) by dragging and dropping the .bin file to the DAPLINK folder, which is a subdirectory of the This PC folder.
    7. The flashing of the .bin file is complete when the MAX32625PICO LED is no longer blinking.
    8. On the MAX32630FTHR, press the reset button next to the white battery connector. After resetting, the LED on the MAX32630FTHR will blink yellow, and then it will blink green.
  3. Open a DOS window by typing DOS in the Windows command search, and then click on Command Prompt.
  4. In the DOS window, type cd c:\maximintegrated\maxrefdes220\hrm
  5. Go to the Windows Device Manager, and then click Ports to expand the listing. Find the COM port number for the USB Serial Device.
  6. Type the following command, replacing the xx with the COM port number for the USB Serial Device and replacing the .msbl name with the latest .msbl name that was downloaded.
    download_fw_over_i2c_host.exe -f "MAX32664_MRD220_MaximFast_X.X.X_VarZ.msbl" -p "COMxx" -d 4
  7. Uninstall previously installed versions of DeviceStudio. Install the latest Maxim DeviceStudio GUI software by double-clicking on the .msi file.

Operating the PC GUI for HRM and SpO2 (MAX32664A)

  1. After the hardware and software installations have been completed, verify that the MAX32630FTHR is connected to the PC using the USB Micro-B cable.
  2. Launch the Maxim DeviceStudio application.
  3. Check Serial over USB under Scan Options.
  4. Press the Scan button to autodetect the MAXREFDES220# that shows as PPG under Connected Devices.
  5. Click Launch Tool to run the MAXREFDES220# HRM and SpO2 specific features.
  6. Select Algorithm Data and AGC to enable the embedded algorithm.
  7. Select Accelerometer Data to display the X-axis and Y-axis accelerometer results from the MAXREFDES220#.
  8. Select Algorithm Data to display the data from the IR and red LED sensors.
  9. Place a steady finger on the MAXREFDES220# sensor.
  10. Select Start Monitoring to observe the data.
  11. The DeviceStudio PC GUI does not support display of data for the blood pressure trending algorithm (MAX32664D).

Trademarks list

  • Android is a registered trademark of Google Inc.
  • Arm is a registered trademark of Arm Limited.
  • IOS is a registered trademark of Cisco Technology, Inc. and is under license to Apple Inc.
  • Mbed is a trademark of Arm Limited.
  • Windows is a registered trademark of Microsoft Corporation.
Quick Start Guide for Heart-Rate Monitoring (HRM) and SpO2 (MAX32664A Evaluation Software)


Ultra-Low Power Biometric Sensor Hub

  • Biometric Sensor Hub Enables Faster Time to Market
  • Finger-Based (Version A) Algorithms Measure
  • Wrist-Based (Version B) Algorithm Measures:

High-Sensitivity Pulse Oximeter and Heart-Rate Sensor for Wearable Health

  • Heart-Rate Monitor and Pulse Oximeter Sensor in LED Reflective Solution
  • Tiny 5.6mm × 3.3mm × 1.55mm 14-Pin Optical Module
  • Ultra-Low Power Operation for Mobile Devices