Intermittent I2C Bus Hang & Data Corruption on MAX30102 (HW-605)
Hi everyone,
I am experiencing a very strange issue with my MAX30102 (HW-605 module) and Arduino Uno.
The Problem:
- The Freeze: When I place my finger on the sensor, the I2C bus intermittently hangs/freezes, stopping all serial output.
- The "Fix" Made it Worse: When I try to solve this by adding external 6.8k ohm pull-up resistors to SDA and SCL, the data becomes corrupted. Instead of valid readings, I start getting garbage values or erratic jumps in the raw data, even before the bus eventually hangs.
Setup:
- MCU: Arduino Uno (ATmega328P)
- Sensor: MAX30102 (HW-605 breakout)
- Power: 3.3V
- Current Pull-ups: 6.8k ohms (External). Note: The module might have internal pull-ups, but adding external ones seems to degrade signal integrity instead of improving it.
Code
/*
Optical Heart Rate Detection (PBA Algorithm) using the MAX30105 Breakout
By: Nathan Seidle @ SparkFun Electronics
Date: October 2nd, 2016
https://github.com/sparkfun/MAX30105_Breakout
This is a demo to show the reading of heart rate or beats per minute (BPM) using
a Penpheral Beat Amplitude (PBA) algorithm.
It is best to attach the sensor to your finger using a rubber band or other tightening
device. Humans are generally bad at applying constant pressure to a thing. When you
press your finger against the sensor it varies enough to cause the blood in your
finger to flow differently which causes the sensor readings to go wonky.
Hardware Connections (Breakoutboard to Arduino):
-5V = 5V (3.3V is allowed)
-GND = GND
-SDA = A4 (or SDA)
-SCL = A5 (or SCL)
-INT = Not connected
The MAX30105 Breakout can handle 5V or 3.3V I2C logic. We recommend powering the board with 5V
but it will also run at 3.3V.
*/
#include <Wire.h>
#include "MAX30105.h"
#include "heartRate.h"
MAX30105 particleSensor;
const byte RATE_SIZE = 4; //Increase this for more averaging. 4 is good.
byte rates[RATE_SIZE]; //Array of heart rates
byte rateSpot = 0;
long lastBeat = 0; //Time at which the last beat occurred
float beatsPerMinute;
int beatAvg;
void setup()
{
Serial.begin(9600);
Serial.println("Initializing...");
// Initialize sensor
if (!particleSensor.begin(Wire, I2C_SPEED_FAST)) //Use default I2C port, 400kHz speed
{
Serial.println("MAX30105 was not found. Please check wiring/power. ");
while (1);
}
Serial.println("Place your index finger on the sensor with steady pressure.");
particleSensor.setup(); //Configure sensor with default settings
particleSensor.setPulseAmplitudeRed(0x0A); //Turn Red LED to low to indicate sensor is running
particleSensor.setPulseAmplitudeGreen(0); //Turn off Green LED
}
void loop()
{
long irValue = particleSensor.getIR();
if (checkForBeat(irValue) == true)
{
//We sensed a beat!
long delta = millis() - lastBeat;
lastBeat = millis();
beatsPerMinute = 60 / (delta / 1000.0);
if (beatsPerMinute < 255 && beatsPerMinute > 20)
{
rates[rateSpot++] = (byte)beatsPerMinute; //Store this reading in the array
rateSpot %= RATE_SIZE; //Wrap variable
//Take average of readings
beatAvg = 0;
for (byte x = 0 ; x < RATE_SIZE ; x++)
beatAvg += rates[x];
beatAvg /= RATE_SIZE;
}
}
Serial.print("IR=");
Serial.print(irValue);
Serial.print(", BPM=");
Serial.print(beatsPerMinute);
Serial.print(", Avg BPM=");
Serial.print(beatAvg);
if (irValue < 50000)
Serial.print(" No finger?");
Serial.println();
}
Link to video/logs:
Thanks in advance!
