text: #ifndef LAGFILTER_H_
  #define LAGFILTER_H_
  
  /*
  
  FIR filter designed with
   http://t-filter.appspot.com
  
  sampling frequency: 625 Hz
  
  fixed point precision: 16 bits
  
  * 0 Hz - 30 Hz
    gain = 0
    desired attenuation = -40 dB
    actual attenuation = n/a
  
  * 40 Hz - 70 Hz
    gain = 1
    desired ripple = 5 dB
    actual ripple = n/a
  
  * 80 Hz - 312 Hz
    gain = 0
    desired attenuation = -40 dB
    actual attenuation = n/a
  
  */
  
  #define LAGFILTER_TAP_NUM 81
  
  typedef struct {
    int history[LAGFILTER_TAP_NUM];
    unsigned int last_index;
  } lagFilter;
  
  void lagFilter_init(lagFilter* f);
  void lagFilter_put(lagFilter* f, int input);
  int lagFilter_get(lagFilter* f);
  
  #endif