yellow line: output of photodiode which detects an LED blue line: output voltage to the LED newfile1: the file without measuring using average of the scope. newfile6: the file with using average of 32 times of the scope. How to filter the noise? It's noisy, I find it's ok to use average of the scope to get the best pattern. but I prefer it to use other method. I try to use bypass capacitor, but it doesn't work. quite disappointed.