qec.h

/*

  @file qec.h
  @author Nicolas Williamson and Thomas Craig 
  @date June 2009

*/

#ifndef __QEC_H__
#define __QEC_H__

//the resolution of the encoder can be 2 or 4
// - QEC_2X: counts interrupts from only one channel; uses state of both channels to infer direciton
// - QEC_4X: counts interrupts from both channels
typedef enum qec_resolution {
  QEC_NULL = 0, 
  QEC_2X = 2, 
  QEC_4X = 4 
} QEC_RESOLUTION;

typedef enum qec_nums {
  QEC_1 = 0, 
  QEC_2 
} QEC_ID;

//the data associated with an encoder
typedef struct qec_data{
  volatile int current_pos; 
  int prev_pos; 
  int delta_pos; 
  int delta_time; 
  int* pos_buf; 
  int* time_buf; 
  int index; 
  int length; 
  float velocity; 
  volatile int prev_chA; 
  volatile int prev_chB; 
  QEC_RESOLUTION resolution; 
} QEC_DATA;

#define QEC_2_PI (6.283185307179586476925286766559f) //approximately

// Functions
//Public
int qec_get_abs_pos(QEC_ID id); //returns the absolute position of the encoder
void qec_update_velocity(void);
float qec_get_velocity(QEC_ID id); //calculates and returns the velocity of an encoder
void qec_init(QEC_RESOLUTION enc_res_1, int enc1_avg_time, QEC_RESOLUTION enc_res_2, int enc2_avg_time, VOID_VOID_F function);
int qec_is_stopped(QEC_ID id);
//Private
void qec_isr(void); //__irq; //interrupt called when a new edge or timer overflow is detected
static void qec_init_data(volatile QEC_DATA* data, QEC_RESOLUTION resolution, int* pos_buf, int* time_buf, int length);
static void qec_calc_velocity(volatile QEC_DATA* data, int ticks_elapsed);
//updates the given encoder with given flag and state information
void qec_update(volatile QEC_DATA* data, int flag_chA, int flag_chB, int chA, int chB);

#endif // __QEC_H__