my module was clearly marked as 3.3v its the one with slots in the board to tie it on your finger
the code has little if any effect on the graphical result. the result depends on your finger and its placement
ambient light etc, my holder is a little tight it constricts circulation a bit and i need to change fingers every 10 minutes to get good data
i found a spare [must have bought 2] i will be more careful with this one.

i still cannot get a algo to find the right peaks. on a graph it looks so obvious even in the crappy reads beats are distinctive, by the absolute shits computers are stupid. breaking the search into 32 sample blocks gets me the block highest highs and lowest lows but there is no guarantee the high in a block is actually a peak or whether continues to ramp up into the next block