transport_delay.h

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/*
 * Copyright (C) 2025 Justin Dubois <j.p.g.dubois@student.tudelft.nl>
 *
 * This file is part of paparazzi
 *
 * paparazzi is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * paparazzi is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with paparazzi; see the file COPYING.  If not, see
 * <http://www.gnu.org/licenses/>.
 */
#ifndef TRANSPORT_DELAY_H
#define TRANSPORT_DELAY_H
 
#include "paparazzi.h"
 
#define TRANSPORT_DELAY_BUFFER_SIZE 20
 
struct TransportDelay {
  uint8_t delay_samples; // Number of samples to delay
  uint8_t write_index; // Current write index
  float buffer[TRANSPORT_DELAY_BUFFER_SIZE];
};
 
 
static inline void init_transport_delay(struct TransportDelay *td, uint8_t delay_samples, const float initial_value)
{
  if (delay_samples > TRANSPORT_DELAY_BUFFER_SIZE) {
    delay_samples = TRANSPORT_DELAY_BUFFER_SIZE;
  }
  td->delay_samples = delay_samples;
  td->write_index = 0;
  for (uint8_t i = 0; i < TRANSPORT_DELAY_BUFFER_SIZE; i++) {
    td->buffer[i] = initial_value;
  }
}
 
static inline float update_transport_delay(struct TransportDelay *td, const float input)
{
  td->buffer[td->write_index] = input;
  uint8_t read_index = (td->write_index + TRANSPORT_DELAY_BUFFER_SIZE - td->delay_samples) % TRANSPORT_DELAY_BUFFER_SIZE;
  float output = td->buffer[read_index];
  td->write_index = (td->write_index + 1) % TRANSPORT_DELAY_BUFFER_SIZE;
  return output;
}
 
static inline void reset_transport_delay(struct TransportDelay *td, const float initial_value)
{
  td->write_index = 0;
  for (uint8_t i = 0; i < TRANSPORT_DELAY_BUFFER_SIZE; i++) {
    td->buffer[i] = initial_value;
  }
}
 
static inline float get_transport_delay(const struct TransportDelay *td)
{
  uint8_t read_index = (td->write_index + TRANSPORT_DELAY_BUFFER_SIZE - td->delay_samples - 1) %
                       TRANSPORT_DELAY_BUFFER_SIZE;
  return td->buffer[read_index];
}
 
#endif // TRANSPORT_DELAY_H