Heart rate sensor MAX30102

[richard]

the filter is not really the issue, its the variability of the data that is problematical, every 128 sample is subtly different.
light leakage, finger pressure and position and even finger compression time lead to wildly variable readings. my max30102 housing is probable not ideal either
i use for this filter
fv = fv*x + nv*(y)

where x+y = 1, fv = average nv = new value

in pbp terms x y
ave = (ave ** 60000) + (buffer[index] ** 5535 ) ;60000 + 5535 = 65535
or
ave = (ave */ 250) + (buffer[index] */ 5 ) ;250+ 5 = 255

depending on finesse required, the introduced phase shift has no bearing on the result either.
it may not be as fast as your method but has better control and in this case speed is of no importance