or, in English:

waveform_value = byte 2
signal_strength = byte 1, low 4 bits
y = (waveform_value * (signal_strength + 1)) / 4.5

The gltches that are smoothed in the spreadsheet are smoothed a bit less than using the (B4*D4)/4 calculation, but are still smoothed.

I do not really prefer the waveform display using this */4.5 calculation, though, to be honest.

Multiplier: My mistake. I thought from your earlier comment that you had multiplied the values with a +2 multiplier. Certainly, those 3 bits can’t be a multiplier when those they are zero!

What’s the error from Python now? (You can email it directly to my.) I’d hoped to have fixed it so you could run tz_cms50.py without pygooglechart.

About the multiplier… I don’t understand if you agree that these bits are a multiplier or not… and why you suspect that we have add 2 to the 3 bit value so that 010 means 4 and not 2?

About the “Flatten out”… I’m still not able to run your code in pyton, so is difficult to understand the problem. With Matlab plots I don’t have problems. The only thing I hat to take care is to convert the integer 8bit value to double precision value before going the multiplication to avoid that non integer values after the multiplication are rounded to an integer.

With respect to the multiplying, would the multipliers be:

000 multiply by 2
001 multiply by 3
010 multiply by 4
011 multiply by 5
100 multiply by 6
101 multiply by 7
110 multiply by 8
111 multiply by 9

All the 000 samples I have recorded have 001000 or 010000 in the low 6 bits of byte 1. And with only two exceptions, the 010000 samples all have heart rates and SpO2 values of zero. 000, 001, 110 and 111 samples are relatively rare in my recorded data.

“Flatten out”. The tz_cms50.py printout scales the waveform star characters’ positions relative to the highest and lowest waveform values seen. After a bit, when the waveform does not have high amplitude waves – is relatively flat – the flatness is enhanced in the tz_cms50.py printout. That is, it’s really, really flat. Always the same “Y” value on-screen. That printout only has 100 vertical “pixels”, but it doesn’t feel right.

I noticed also sometimes the 5th bit in byte1. This is not for sure related with the multiplicator… it seems to appear just before a “beat” bit if has lost the previous “beats”…

It does look like they only change those 3 low bits at the time of the beat.

They tend to go down in value when the average for recent beat samples goes lower than some variable level. And they tend to go up when the average of recent beat samples goes above some variable level.

Too, I notice that the low 3 bits sometimes go down just a few samples before the waveform hits zero for a run of samples. And, the low 3 bits sometimes go up a similar number of samples after the waveform hits near 127 for a run of samples.

I’ll have to try that multiply idea. I had rejected it because it seemed like it would be too powerful – have too much effect on the waveform values.