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oxullo / Arduino-MAX30100

Arduino library for MAX30100, integrated oximeter and heart rate sensor
GNU General Public License v3.0
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Getting strange pulses each 2 seconds #32

Closed bestware closed 6 years ago

bestware commented 6 years ago

Troubleshooting checklist

Description of the issue

Using the debug-prog + rolling graph can see strange pulses occuring exactly every 2 seconds! (Very high peak followed by some negative samples) - then ok till next peak.

No idea where this peaks come from (visible in Serial monitor as well) 2sec_pulses

Output from MAX30100_Tester example

Initializing MAX30100..Success Enabling HR/SPO2 mode..done. Configuring LEDs biases to 50mA..done. Initializing MAX30100..Success Enabling HR/SPO2 mode..done. Configuring LEDs biases to 50mA..done. Lowering the current to 7.6mA..done. Shutting down..done. Resuming normal operation..done. Sampling die temperature..done, temp=38.56C All test pass. Press any key to go into sampling loop mode

Details of my setup

oxullo commented 6 years ago

@bestware thanks for pointing it out. It's surely a regression caused by b2fa5675 and it could be also the reason for a bunch of reports regarding the unreliable bpm count.

oxullo commented 6 years ago

@bestware could you give a try to the branch https://github.com/oxullo/Arduino-MAX30100/tree/issues/%2332/workaround ?

bestware commented 6 years ago

Great - works like a charm! Thank you for quick reply. hr_ok

oxullo commented 6 years ago

It looks to me that it's a bug of the MAX30100. The flag to start the temperature readout must be set on register 0x6, which controls the operating mode of the sensor and I guess that setting this register triggers a momentary shutdown of the LED drivers, injecting a transient in the samples series and temporarily blinding the bpm counter. In the new design, MAX30102 the temperature enable flag has been silently moved to a different register..

I fixed it by removing the temperature poller from the PulseOximeter class. The change is in master and it will be released soon.