Protocentral Pulse Express with MAX30102 and MAX32664D

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Pulse Express is a compact breakout that pairs a high-sensitivity MAX30102 optical sensor with a MAX32664D biometric sensor hub. The MAX32664D runs Maxim/ADI's on-chip Blood-Pressure-Trending (BPT) algorithm and reports calculated heart rate, SpO2 and blood-pressure-trend data over I2C, so the host MCU does no signal processing. Suitable for finger-based wearable health R&D.

Note: This device is for research & development only and is NOT a medical device. It is not FDA, CE or FCC approved for consumer use.

Overview

Key capabilities (all exposed by this library):

• Raw PPG streaming (IR + Red, 24-bit ADC counts)
• Heart rate and SpO2 with per-reading confidence
• Blood-pressure trending — calibration → estimation (systolic / diastolic)
• SpO2 coefficient calibration (per Maxim AN6845)
• Multi-subject calibration, up to 5 subjects (firmware >= 40.5.0)
• Heart-rate variability (SDNN / RMSSD) from inter-beat intervals
• Runtime firmware-version detection and capability adaptation (40.x line)
• Factory / recovery firmware flasher for the MAX32664 bootloader

Installation

Arduino Library Manager (recommended): search for ProtoCentral Pulse Express and click Install.

Manual: download this repository as a ZIP and use Sketch -> Include Library -> Add .ZIP Library... in the Arduino IDE.

Hardware Setup

MAX32664 pin	Arduino UNO / R4	ESP32 (example)	Function
SDA	A4	GPIO21	I2C data
SCL	A5	GPIO22	I2C clock
Vin	5V	5V / VIN	Power
GND	GND	GND	Ground
MFIO	D2	any GPIO	Data-ready / mode
RESET	D4	any GPIO	Hub reset

The RESET and MFIO pins are passed to the constructor, so any GPIOs work.

Quick Start

#include <Wire.h>
#include "protocentral_pulse_express.h"

PulseExpress hub(/*RESET=*/4, /*MFIO=*/2);

void setup() {
  Serial.begin(57600);
  Wire.begin();
  if (hub.begin() != PulseExpressStatus::Ok) { /* handle error */ }
  hub.startEstimation();                 // streams HR + SpO2 (BP needs calibration)
}

void loop() {
  PulseExpressSample s[8];
  size_t n = 0;
  if (hub.readSamples(s, 8, &n) == PulseExpressStatus::Ok)
    for (size_t i = 0; i < n; ++i) {
      Serial.print("HR ");    Serial.print(s[i].heartRate(), 1);
      Serial.print(" SpO2 "); Serial.println(s[i].spo2(), 1);
    }
}

Firmware versions & capabilities

The MAX32664D changed its protocol across the 40.x firmware line. begin() reads the hub firmware version and derives a capability set (hub.caps()); the driver then adapts automatically. Notable breakpoints:

• 40.2.2+ — BP-medication / rest-mode setup steps dropped.
• 40.5.0+ — calibration vector 824 -> 512 bytes, sample 23 -> 29 bytes, date format YYMMDD -> YYYYMMDD, and multi-point calibration (calIndex 0..4).

Branch on hub.caps().multiPointCalib if you support both. Version checking is a soft warning: begin() still proceeds on unexpected firmware and reports it via hub.firmwareSupported().

Firmware is pre-installed at the factory. Boards ship flashed and ready; you do not need a firmware image for normal use. The MAX32664D application image (.msbl) is Maxim/ADI IP and is not redistributed here. Re-flashing is a factory/recovery operation — see examples/11.FirmwareFlash and extras/.

Examples

#	Sketch	Shows
01	RawPPGStreamPlotter	Raw IR PPG to Arduino Serial Plotter
02	RawPPGStreamOpenView	Raw IR/Red to ProtoCentral OpenView GUI
03	HeartRateSpO2	Live heart rate + SpO2 (no calibration)
04	BPTCalibration	Run BPT calibration, dump the vector
05	BPTEstimation	Estimate BP/HR/SpO2 from a saved vector
06	BPTCalibrateAndEstimate	Full calibrate -> estimate, end to end
07	SaveLoadCalibrationEEPROM	Persist the vector to EEPROM, reload on boot
08	MultiSubjectCalibration	Calibrate up to 5 subjects (FW >= 40.5.0)
09	HeartRateVariability	SDNN / RMSSD from inter-beat intervals
10	DeviceInfoAndDiagnostics	Firmware versions, caps, live hub status
11	FirmwareFlash	Factory/recovery .msbl flasher

Hub firmware flashing (factory / recovery)

Boards ship pre-flashed — you normally never need this. To recover a hub or change its MAX32664D firmware version, flash-firmware.sh uploads the 11.FirmwareFlash relay sketch and then streams your .msbl to it:

./flash-firmware.sh --dry-run  extras/firmware/<image>.msbl   # parse only
./flash-firmware.sh --esp32 --port <PORT> extras/firmware/<image>.msbl

Host board: a page write is one 8210-byte I2C transaction, so the host's Wire buffer must hold all of it — use an ESP32 or RP2040. The UNO R4 cannot flash (its Renesas Wire caps transactions at 255 bytes); the tool detects this and stops before erasing anything.

The .msbl is Maxim/ADI IP and is not distributed with this library; supply your own. Full usage, the manual two-command path, and troubleshooting are in extras/flash_tool/README.md.

API Reference

Construct with the reset and MFIO pins (and optionally a TwoWire bus): PulseExpress hub(resetPin, mfioPin, Wire);

• begin() — reset hub, enter application mode, read version, derive caps.
• version(), algoVersion(), caps(), firmwareSupported() — device info.
• BPT calibration: startCalibration(...), readSample(...), readCalibrationVector(...).
• BPT estimation: loadCalibrationVector(...), startEstimation(...), readSamples(...).
• Raw PPG: startRaw(), readRaw(...).
• Diagnostics / teardown: readStatus(...), stop().

All fallible calls return PulseExpressStatus; compare against PulseExpressStatus::Ok. See src/protocentral_pulse_express.h for the full documented API.

Migrating from 2.0.x: the class was Max32664 with Max32664* types. Those names still work via #include "max32664.h". New code should use PulseExpress and #include "protocentral_pulse_express.h". See CHANGELOG.md.

For further details

Refer to the Pulse Express documentation.

License Information

This product is open source! Both our hardware and software are open source and licensed under the following licenses:

Hardware — CERN-OHL-P v2. Copyright CERN 2020.

Software — MIT License.

Documentation — Creative Commons Share-alike 4.0 International.

See LICENSE.md for the detailed license descriptions.