MMDVM/DMRDMOTX.cpp

/*
 *   Copyright (C) 2009-2017 by Jonathan Naylor G4KLX
 *   Copyright (C) 2016 by Colin Durbridge G4EML
 *   Copyright (C) 2017 by Andy Uribe CA6JAU
 *
 *   This program 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 of the License, or
 *   (at your option) any later version.
 *
 *   This program 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 this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include "Config.h"
#include "Globals.h"
#include "DMRSlotType.h"

// Generated using rcosdesign(0.2, 8, 10, 'sqrt') in MATLAB
static q15_t RRC_0_2_FILTER[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 850, 592, 219, -234, -720, -1179,
                                -1548, -1769, -1795, -1597, -1172, -544, 237, 1092, 1927, 2637,
                                3120, 3286, 3073, 2454, 1447, 116, -1431, -3043, -4544, -5739,
                                -6442, -6483, -5735, -4121, -1633, 1669, 5651, 10118, 14822,
                                19484, 23810, 27520, 30367, 32156, 32767, 32156, 30367, 27520,
                                23810, 19484, 14822, 10118, 5651, 1669, -1633, -4121, -5735,
                                -6483, -6442, -5739, -4544, -3043, -1431, 116, 1447, 2454,
                                3073, 3286, 3120, 2637, 1927, 1092, 237, -544, -1172, -1597,
                                -1795, -1769, -1548, -1179, -720, -234, 219, 592, 850}; // numTaps = 90, L = 10
const uint16_t RRC_0_2_FILTER_PHASE_LEN = 9U; // phaseLength = numTaps/L

const q15_t DMR_LEVELA =  1362;
const q15_t DMR_LEVELB =  454;
const q15_t DMR_LEVELC = -454;
const q15_t DMR_LEVELD = -1362;

const uint8_t BIT_MASK_TABLE[] = {0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U, 0x02U, 0x01U};

#define WRITE_BIT1(p,i,b) p[(i)>>3] = (b) ? (p[(i)>>3] | BIT_MASK_TABLE[(i)&7]) : (p[(i)>>3] & ~BIT_MASK_TABLE[(i)&7])
#define READ_BIT1(p,i)    (p[(i)>>3] & BIT_MASK_TABLE[(i)&7])

const uint8_t DMR_SYNC = 0x5FU;

CDMRDMOTX::CDMRDMOTX() :
m_fifo(),
m_modFilter(),
m_modState(),
m_poBuffer(),
m_poLen(0U),
m_poPtr(0U),
m_txDelay(240U)       // 200ms
{
  ::memset(m_modState, 0x00U, 16U * sizeof(q15_t));

  m_modFilter.L           = DMR_RADIO_SYMBOL_LENGTH;
  m_modFilter.phaseLength = RRC_0_2_FILTER_PHASE_LEN;
  m_modFilter.pCoeffs     = RRC_0_2_FILTER;
  m_modFilter.pState      = m_modState;
}

void CDMRDMOTX::process()
{
  if (m_poLen == 0U && m_fifo.getData() > 0U) {
    if (!m_tx) {
      for (uint16_t i = 0U; i < m_txDelay; i++)
        m_poBuffer[i] = DMR_SYNC;

      m_poLen = m_txDelay;
    } else {
      for (unsigned int i = 0U; i < 72U; i++)
        m_poBuffer[i] = DMR_SYNC;

      for (unsigned int i = 0U; i < DMR_FRAME_LENGTH_BYTES; i++)
        m_poBuffer[i + 39U] = m_fifo.get();

      m_poLen = 72U;
    }

    m_poPtr = 0U;
  }

  if (m_poLen > 0U) {
    uint16_t space = io.getSpace();
    
    while (space > (4U * DMR_RADIO_SYMBOL_LENGTH)) {
      uint8_t c = m_poBuffer[m_poPtr++];

      writeByte(c);

      space -= 4U * DMR_RADIO_SYMBOL_LENGTH;
      
      if (m_poPtr >= m_poLen) {
        m_poPtr = 0U;
        m_poLen = 0U;
        return;
      }
    }
  }
}

uint8_t CDMRDMOTX::writeData(const uint8_t* data, uint8_t length)
{
  if (length != (DMR_FRAME_LENGTH_BYTES + 1U))
    return 4U;

  uint16_t space = m_fifo.getSpace();
  if (space < DMR_FRAME_LENGTH_BYTES)
    return 5U;

  for (uint8_t i = 0U; i < DMR_FRAME_LENGTH_BYTES; i++)
    m_fifo.put(data[i + 1U]);

  return 0U;
}

void CDMRDMOTX::writeByte(uint8_t c)
{
  q15_t inBuffer[4U];
  q15_t outBuffer[DMR_RADIO_SYMBOL_LENGTH * 4U];

  const uint8_t MASK = 0xC0U;

  for (uint8_t i = 0U; i < 4U; i++, c <<= 2) {
    switch (c & MASK) {
      case 0xC0U:
        inBuffer[i] = DMR_LEVELA;
        break;
      case 0x80U:
        inBuffer[i] = DMR_LEVELB;
        break;
      case 0x00U:
        inBuffer[i] = DMR_LEVELC;
        break;
      default:
        inBuffer[i] = DMR_LEVELD;
        break;
    }
  }

  ::arm_fir_interpolate_q15(&m_modFilter, inBuffer, outBuffer, 4U);

  io.write(STATE_DMR, outBuffer, DMR_RADIO_SYMBOL_LENGTH * 4U);
}

uint8_t CDMRDMOTX::getSpace() const
{
  return m_fifo.getSpace() / (DMR_FRAME_LENGTH_BYTES + 2U);
}

void CDMRDMOTX::setTXDelay(uint8_t delay)
{
  m_txDelay = 600U + uint16_t(delay) * 12U;        // 500ms + tx delay

  if (m_txDelay > 1200U)
    m_txDelay = 1200U;
}