text: /* ----------------------------------------------------------------------
   * Project:      CMSIS DSP Library
   * Title:        arm_pid_init_q15.c
   * Description:  Q15 PID Control initialization function
   *
   * $Date:        18. March 2019
   * $Revision:    V1.6.0
   *
   * Target Processor: Cortex-M cores
   * -------------------------------------------------------------------- */
  /*
   * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
   *
   * SPDX-License-Identifier: Apache-2.0
   *
   * Licensed under the Apache License, Version 2.0 (the License); you may
   * not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an AS IS BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #include "dsp/controller_functions.h"
  
  /**
    @addtogroup PID
    @{
   */
  
  /**
    @brief         Initialization function for the Q15 PID Control.
    @param[in,out] S               points to an instance of the Q15 PID structure
    @param[in]     resetStateFlag
                     - value = 0: no change in state
                     - value = 1: reset state
    @return        none
  
    @par           Details
                     The <code>resetStateFlag</code> specifies whether to set state to zero or not. \n
                     The function computes the structure fields: <code>A0</code>, <code>A1</code> <code>A2</code>
                     using the proportional gain( \c Kp), integral gain( \c Ki) and derivative gain( \c Kd)
                     also sets the state variables to all zeros.
   */
  
  void arm_pid_init_q15(
    arm_pid_instance_q15 * S,
    int32_t resetStateFlag)
  {
  
  #if defined (ARM_MATH_DSP)
  
    /* Derived coefficient A0 */
    S->A0 = __QADD16(__QADD16(S->Kp, S->Ki), S->Kd);
  
    /* Derived coefficients and pack into A1 */
  
  #ifndef  ARM_MATH_BIG_ENDIAN
    S->A1 = __PKHBT(-__QADD16(__QADD16(S->Kd, S->Kd), S->Kp), S->Kd, 16);
  #else
    S->A1 = __PKHBT(S->Kd, -__QADD16(__QADD16(S->Kd, S->Kd), S->Kp), 16);
  #endif
  
  #else
  
    q31_t temp;                                    /* to store the sum */
  
    /* Derived coefficient A0 */
    temp = S->Kp + S->Ki + S->Kd;
    S->A0 = (q15_t) __SSAT(temp, 16);
  
    /* Derived coefficients and pack into A1 */
    temp = -(S->Kd + S->Kd + S->Kp);
    S->A1 = (q15_t) __SSAT(temp, 16);
    S->A2 = S->Kd;
  
  #endif /* #if defined (ARM_MATH_DSP) */
  
    /* Check whether state needs reset or not */
    if (resetStateFlag)
    {
      /* Reset state to zero, The size will be always 3 samples */
      memset(S->state, 0, 3U * sizeof(q15_t));
    }
  
  }
  
  /**
    @} end of PID group
   */
  