iir_filter

[anatolyk69_gmail.c]

This part isn't correct:

float filter( float x) {
  float v[6];
  for(int i=0; i <= 5; i++)
	v[i]=0.0;

You declare new array each time when you passing new value, so all history is lost. I think you should declare v[6] as global and remove "for" initializing loop.