Not an issue--trying to help

[benjsmi]

Hello @iphands ... I have ordered a CMS 50D+ (http://www.amazon.com/gp/product/B00B8L8ZXE/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1) and also am getting ready to hack it from a Debian Linux system.

Your write-up on your site (http://ian.ahands.org/progs/pulseox/) says that you aren't sure about how they are using byte 4 to represent pulses > 127, and similarly that you have "pins" or bytes that don't seem to make sense (byte 3).

I found this blog post, by a fellow tinkerer who is mostly complaining about the 5-byte protocol you describe, but in his complaining, he does a great deal of explanation about how the protocol for the CM50D+ works!

http://www.tranzoa.net/~alex/blog/?p=371

He even has a link to a PDF spec that he dug up from somewhere that indicates what each bit in the sequence represents.

https://www.tranzoa.net/~alex/blog/images/Communication%20protocol.pdf

Let me know if this helps at all.