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Strange Optical Signal Noise with ADPD107

Question asked by szabadaba on Sep 1, 2017
Latest reply on Oct 3, 2017 by szabadaba

Hi Buckley, I am currently using the ADPD107 for PPG sensing. I am getting some strange looking noise on the optical signal inconsistently. It seems to be more of a problem when sampling at lower LED brightnesses, but it is not always consistently noisy.This is what it looks like when it is really bad:

and sometimes it looks like this, with less frequent spikes:

 

Aside from electrical issues with the boards (which we are investigating), is this anything you have seen before and can diagnose? We are using a setup with 3 LEDs and 2 photodiodes. I believe I have optimized the timing correctly. Here is a dump of all the registers, perhaps are settings are causing this:

Register (Hex)Value (hex)
08000
1FF
2204
6700
8516
9C8
A0
B1
D0
F0
102
111131
1250
1455D
150
182000
192000
1A2000
1B2000
1E2000
1F2000
202000
212000
221004
23300C
243001
25F1C
30320
31818
340
35320
36818
370
380
3922D4
3B22D4
3C3006
421C37
43ADA5
441C37
45ADA5
4B2692
4D98
4E60
4F2090
500
5420
550
580
5A0
5F0

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