enc.c

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// **************************************************************************
// the includes

#include "sw/modules/enc/src/32b/enc.h"


// **************************************************************************
// the defines


// **************************************************************************
// the globals

// **************************************************************************
// the functions

ENC_Handle ENC_init(void *pMemory,const size_t numBytes)
{
  ENC_Handle encHandle;
  
  if(numBytes < sizeof(ENC_Obj))
    return((ENC_Handle)NULL);

  // assign the handle
  encHandle = (ENC_Handle)pMemory;
  
  return(encHandle);
} // end of ENC_init() function

void ENC_setup(ENC_Handle encHandle, const int16_t sample_period, const uint16_t num_pole_pairs, const uint16_t num_enc_slots, const uint32_t enc_zero_offset, const float_t full_scale_freq, const float_t speed_update_freq, const float_t speed_cutoff)
{
  ENC_Obj *enc;
  float_t temp;
  float_t speed_cutoff_radians;
  int16_t i;
 
  // create an object pointer for manipulation
  enc = (ENC_Obj *)encHandle;
  
  // setup the encoder sample rate
  enc->sample_count = 0;
  enc->sample_period = sample_period;
  
  // copy the parameters into the data structure
  enc->num_enc_slots = num_enc_slots;
  enc->num_pole_pairs = num_pole_pairs;
  enc->enc_zero_offset = enc_zero_offset;
  enc->full_scale_freq = full_scale_freq;
  enc->delta_enc = 0;
  enc->prev_enc = 0;
  
  // initialize the electrical angle
  enc->enc_elec_angle = 0;
    
  // compute the gain which translates the mech into the elec angle
  enc->mech_angle_gain = (_iq)((((uint32_t)1)<<24)/(4*num_enc_slots));

  // compute the speed gain
  temp = ((float_t)num_pole_pairs*speed_update_freq*ENC_SPEED_SCALING_FACTOR) / (4.0*(float_t)num_enc_slots*full_scale_freq*(float_t)sample_period);
  enc->speed_gain = (int32_t) temp;
  
  // compute the rpm gain
  temp = (float_t)((full_scale_freq*60.0)/num_pole_pairs);
  enc->rpm_gain = (int32_t) temp;
  
  // compute the speed coefficients and initialize the low-pass filtered output
  enc->speed_cutoff = speed_cutoff;
  speed_cutoff_radians = ENC_2PI*speed_cutoff;
  temp = speed_cutoff_radians/(speed_update_freq+speed_cutoff_radians);
  enc->speed_lpf_cx = (int32_t) (ENC_SPEED_COEFF_SCALING*temp);
  enc->speed_lpf_cy = ENC_SPEED_COEFF_SCALING - enc->speed_lpf_cx;
  enc->speed_lpf_out = 0;
  
  // setup the encoder log
  enc->log_state        = ENC_LOG_STATE_IDLE;
  enc->run_flag         = 0;
  enc->trigger_idx      = 0;
  enc->trigger_delta    = 0;  
  enc->log_idx          = 0;
  enc->post_trigger_len = ENC_LOG_LEN>>1;
  enc->post_trigger_cnt = enc->post_trigger_len;
  for (i=0; i<ENC_LOG_LEN; i++)
  {
        enc->log[i] = 0;
  }
  
  return;
} // end of ENC setup function


void ENC_calcElecAngle(ENC_Handle encHandle, uint32_t posnCounts)
{
        ENC_Obj *enc;
        uint32_t temp;
 
  // create an object pointer for manipulation
  enc = (ENC_Obj *) encHandle;
        
  // compute the mechanical angle
  temp = posnCounts*enc->mech_angle_gain;
  // add in calibrated offset
  temp += enc->enc_zero_offset;
  // convert to electrical angle
  temp = temp * enc->num_pole_pairs;
  // wrap around 1.0 (Q24)
  temp &= ((uint32_t) 0x00ffffff);
  // store encoder electrical angle
  enc->enc_elec_angle = (_iq)temp;
  // update the slip angle
  enc->enc_slip_angle = enc->enc_slip_angle + enc->incremental_slip;
  // wrap around 1.0 (Q24)
  enc->enc_slip_angle &= ((uint32_t) 0x00ffffff);
  // add in compensation for slip
  temp = temp + enc->enc_slip_angle;
  // wrap around 1.0 (Q24)
  temp &= ((uint32_t) 0x00ffffff);
  // store encoder magnetic angle
  enc->enc_magnetic_angle = (_iq)temp;
  
  return;
} // end of ENC_calc_elec_angle() function



void ENC_run(ENC_Handle encHandle, uint32_t posnCounts, uint16_t indextFlag, uint16_t dirFlag, int16_t log_flag)
{
        uint16_t dir;
        uint16_t index_event_before;
        uint16_t index_event_after;
        ENC_Obj *enc;
        int32_t enc_val;
        int32_t delta_enc;
        int32_t temp;
        int16_t sample_count;
 
  // create an object pointer for manipulation
  enc = (ENC_Obj *) encHandle;
  
  // update the encoder counter
  sample_count = enc->sample_count;
  sample_count++;
  
  // if it reaches the sample period, read and process encoder data
  if (sample_count == enc->sample_period)
  {
    enc->sample_count = 0;
    
    // check for index event before the encoder reading
    index_event_before = indextFlag;
        
    // read the encoder
    enc_val = posnCounts;
        
    // compute the mechanical angle
    // compute the mechanical angle
    temp = (enc_val)*enc->mech_angle_gain;
    // add in calibrated offset
    temp += enc->enc_zero_offset;
    // convert to electrical angle
    temp = temp * enc->num_pole_pairs;
    // wrap around 1.0
    temp &= ((uint32_t) 0x00ffffff);

    enc->enc_elec_angle = (_iq)temp;
  
    /*********************/
    /* compute the SPEED */
    /*********************/
  
    // read QEP direction from quadrature direction latch flag
    dir = dirFlag;
  
    // check for index event after the encoder reading
    index_event_after = indextFlag;
  
    // handle a rollover event
    if (index_event_after)
    {
           if (dir)
           {
             delta_enc = enc_val + (4*enc->num_enc_slots-1) - enc->prev_enc;
           }
           else
           {
         delta_enc = enc->prev_enc + (4*enc->num_enc_slots-1) - enc_val;
           }
    }
    else
    {
       delta_enc = enc_val - enc->prev_enc;
    }
    
    // save off the delta encoder value in the data structure only if the index event before and after are the same
    if ((index_event_after == index_event_before) && (abs(delta_enc) < enc->num_enc_slots))
        enc->delta_enc = delta_enc;
    
    // log the startup data
    switch(enc->log_state)
    {
        // wait for run flag to be set
        case ENC_LOG_STATE_IDLE:
        {
                if (enc->run_flag)
                {
                        enc->run_flag  = 0;
                        enc->log_idx   = 0;
                        enc->log_state = ENC_LOG_STATE_FREERUN;
                }
        }
        break;
        
        // collect data round robin until there's a trigger event
        case ENC_LOG_STATE_FREERUN:
        {
                        enc->log[enc->log_idx] = (int16_t)enc_val;
                        enc->log_idx = enc->log_idx + 1;
                        if (enc->log_idx > ENC_LOG_LEN)
                                enc->log_idx = 0;
                        if (abs(delta_enc)>ENC_LOG_DELTA_TRIGGER_THRES)
                        {
                                enc->trigger_delta = delta_enc;
                                enc->trigger_idx = enc->log_idx;
                                enc->post_trigger_cnt = enc->post_trigger_len;
                                enc->log_state = ENC_LOG_STATE_ACQUIRE;
                        }
        }               
        break;
        
        // when trigger occurs collect 1/2 a buffer of post-trigger information
        case ENC_LOG_STATE_ACQUIRE:
        {
                        enc->log[enc->log_idx] = (int16_t)enc_val;
                        enc->log_idx = enc->log_idx + 1;
                        if (enc->log_idx > ENC_LOG_LEN)
                                enc->log_idx = 0;
                        enc->post_trigger_cnt = enc->post_trigger_cnt - 1;
                        if (enc->post_trigger_cnt == 0)
                                enc->log_state = ENC_LOG_STATE_IDLE;
        }       
        break;
    }

    // shift it to Q24
    temp = enc->delta_enc*enc->speed_gain;
  
    // LPF the encoder
    temp = (enc->speed_lpf_cy)*enc->speed_lpf_out + (enc->speed_lpf_cx)*temp;
    temp >>= ENC_SPEED_COEFF_Q;
    enc->speed_lpf_out = temp;

    // copy the current into the previous value  
    enc->prev_enc = enc_val;
  }
  else
  {
        enc->sample_count = sample_count;
  }
  
} // end of ENC_run() function


int16_t ENC_getSpeedRPM(ENC_Handle encHandle)
{
        ENC_Obj *enc;
        _iq temp;
 
  // create an object pointer for manipulation
  enc = (ENC_Obj *) encHandle;
  
  temp = (enc->speed_lpf_out >> ENC_RPM_Q1);
  temp = (temp * enc->rpm_gain) >> ENC_RPM_Q2;
        
  return (int16_t) temp;
} // end of ENC_getSpeedRPM() function


// end of file