Pulse sensor w/Teensy board about pulsesensorplayground HOT 5 CLOSED

@dsiah

1. When using the hardware timer, you are sure to get a very regular sample rate, which is important for doing DSP on analog signals. That ensures that our derivation of BPM values is accurate. Using a software timer means that the main loop in the program has to check the time to see if it's time to read the sensor. This can cause jitter in the timing of the analog readings, which will effect accuracy of the BPM values. Both our hardware and software timers are set up to read at 500Hz (2mS sample rate). That, according to some science that I read, is good enough to get accurate heart rate data. If you're using the software timer, you have to be mindful in your code not to get too caught up in some activity for more than 2mS to ensure that you don't miss a sample reading.

We do have some statistical analysis code in the Playground to get a baseline of your sample accuracy when running either timer. A tutorial on that is forthcoming.

2. Right now, I'm wrapping up a tutorial on how to connect Pulse Sensor to Raspberry Pi. When I'm done with that, I will jump on the Teensy family.

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@dsiah Well, the Teensy does have interrupts that would work with Pulse Sensor, but they're not implemented yet. We plan to, and we're working toward this eventual hardware support.
For now, please use the PulseSensor_BPM_Alternative code example to start with. It uses a software timer interrupt, and it can be implemented with very little jitter.

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Lovely, I was able to compile that, as a follow up:

1. What is the key difference between using the software timer interrupt and the hardware support?
2. Is there a timeline for the hardware support?

Thank you!

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@dsiah
I'm jumping into this and noticing some things about your original issue.
First, it looks like you're compiling an unsupported code base.
The PulseSensorAmped_Arduino_1.5.0.ino has been superseded by the PulseSensor Playground Library. Right now, the best example sketch to use is the PulseSensor_BPM_Alternative.ino sketch.
This will compile and run on Teensy boards, but we don't have the timer interrupt worked out yet.
Please use the new library.

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Thanks @biomurph I've been using this and hope the issue directs others in my situation to use that sketch.

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