mirror of https://github.com/markqvist/MMDVM.git
263 lines
7.2 KiB
C++
263 lines
7.2 KiB
C++
/*
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* Copyright (C) 2016 by Jonathan Naylor G4KLX
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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// #define WANT_DEBUG
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#include "Config.h"
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#include "Globals.h"
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#include "P25RX.h"
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#include "Utils.h"
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const unsigned int BUFFER_LENGTH = 200U;
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const q15_t SCALING_FACTOR = 18750; // Q15(0.55)
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const uint32_t PLLMAX = 0x10000U;
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const uint32_t PLLINC = PLLMAX / P25_RADIO_SYMBOL_LENGTH;
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const uint32_t INC = PLLINC / 32U;
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const uint8_t SYNC_SYMBOL_ERRS = 0U;
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const uint8_t SYNC_BIT_START_ERRS = 2U;
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const uint8_t SYNC_BIT_RUN_ERRS = 4U;
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const unsigned int MAX_SYNC_FRAMES = 3U + 1U;
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const uint8_t BIT_MASK_TABLE[] = {0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U, 0x02U, 0x01U};
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#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])
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#define READ_BIT1(p,i) (p[(i)>>3] & BIT_MASK_TABLE[(i)&7])
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CP25RX::CP25RX() :
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m_pll(0U),
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m_prev(false),
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m_state(P25RXS_NONE),
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m_bitBuffer(0x00U),
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m_symbols(),
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m_outBuffer(),
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m_buffer(NULL),
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m_bufferPtr(0U),
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m_symbolPtr(0U),
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m_lostCount(0U),
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m_centre(0),
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m_threshold(0)
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{
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m_buffer = m_outBuffer + 1U;
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}
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void CP25RX::reset()
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{
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m_pll = 0U;
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m_prev = false;
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m_state = P25RXS_NONE;
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m_bitBuffer = 0x00U;
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m_bufferPtr = 0U;
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m_symbolPtr = 0U;
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m_lostCount = 0U;
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m_centre = 0;
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m_threshold = 0;
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}
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void CP25RX::samples(const q15_t* samples, uint8_t length)
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{
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for (uint16_t i = 0U; i < length; i++) {
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bool bit = samples[i] < 0;
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if (bit != m_prev) {
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if (m_pll < (PLLMAX / 2U))
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m_pll += INC;
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else
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m_pll -= INC;
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}
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m_prev = bit;
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m_pll += PLLINC;
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if (m_pll >= PLLMAX) {
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m_pll -= PLLMAX;
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if (m_state == P25RXS_NONE)
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processNone(samples[i]);
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else
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processData(samples[i]);
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}
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}
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}
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void CP25RX::processNone(q15_t sample)
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{
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m_symbolBuffer <<= 1;
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if (sample < 0)
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m_symbolBuffer |= 0x01U;
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m_symbols[m_symbolPtr] = sample;
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// Fuzzy matching of the data sync bit sequence
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if (countBits32((m_symbolBuffer & P25_SYNC_SYMBOLS_MASK) ^ P25_SYNC_SYMBOLS) <= SYNC_SYMBOL_ERRS) {
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q15_t max = -16000;
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q15_t min = 16000;
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for (uint8_t i = 0U; i < P25_SYNC_LENGTH_SYMBOLS; i++) {
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q15_t val = m_symbols[i];
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if (val > max)
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max = val;
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if (val < min)
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min = val;
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}
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q15_t centre = (max + min) >> 1;
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q31_t v1 = (max - centre) * SCALING_FACTOR;
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q15_t threshold = q15_t(v1 >> 15);
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uint16_t ptr = m_symbolPtr + 1U;
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if (ptr >= P25_SYNC_LENGTH_SYMBOLS)
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ptr = 0U;
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for (uint8_t i = 0U; i < P25_SYNC_LENGTH_SYMBOLS; i++) {
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q15_t sample = m_symbols[ptr] - centre;
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if (sample < -threshold) {
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m_bitBuffer <<= 2;
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m_bitBuffer |= 0x01U;
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} else if (sample < 0) {
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m_bitBuffer <<= 2;
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m_bitBuffer |= 0x00U;
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} else if (sample < threshold) {
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m_bitBuffer <<= 2;
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m_bitBuffer |= 0x02U;
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} else {
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m_bitBuffer <<= 2;
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m_bitBuffer |= 0x03U;
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}
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ptr++;
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if (ptr >= P25_SYNC_LENGTH_SYMBOLS)
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ptr = 0U;
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}
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// Fuzzy matching of the data sync bit sequence
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if (countBits64((m_bitBuffer & P25_SYNC_BITS_MASK) ^ P25_SYNC_BITS) <= SYNC_BIT_START_ERRS) {
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DEBUG5("P25RX: sync found in None min/max/centre/threshold", min, max, centre, threshold);
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for (uint8_t i = 0U; i < P25_SYNC_LENGTH_BYTES; i++)
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m_buffer[i] = P25_SYNC_BYTES[i];
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m_centre = centre;
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m_threshold = threshold;
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m_lostCount = MAX_SYNC_FRAMES;
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m_bufferPtr = P25_SYNC_LENGTH_BITS;
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m_state = P25RXS_DATA;
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io.setDecode(true);
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io.setADCDetection(true);
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}
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}
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m_symbolPtr++;
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if (m_symbolPtr >= P25_SYNC_LENGTH_SYMBOLS)
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m_symbolPtr = 0U;
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}
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void CP25RX::processData(q15_t sample)
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{
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sample -= m_centre;
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if (sample < -m_threshold) {
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m_bitBuffer <<= 2;
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m_bitBuffer |= 0x01U;
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WRITE_BIT1(m_buffer, m_bufferPtr, false);
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m_bufferPtr++;
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WRITE_BIT1(m_buffer, m_bufferPtr, true);
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m_bufferPtr++;
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} else if (sample < 0) {
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m_bitBuffer <<= 2;
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m_bitBuffer |= 0x00U;
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WRITE_BIT1(m_buffer, m_bufferPtr, false);
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m_bufferPtr++;
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WRITE_BIT1(m_buffer, m_bufferPtr, false);
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m_bufferPtr++;
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} else if (sample < m_threshold) {
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m_bitBuffer <<= 2;
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m_bitBuffer |= 0x02U;
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WRITE_BIT1(m_buffer, m_bufferPtr, true);
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m_bufferPtr++;
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WRITE_BIT1(m_buffer, m_bufferPtr, false);
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m_bufferPtr++;
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} else {
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m_bitBuffer <<= 2;
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m_bitBuffer |= 0x03U;
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WRITE_BIT1(m_buffer, m_bufferPtr, true);
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m_bufferPtr++;
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WRITE_BIT1(m_buffer, m_bufferPtr, true);
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m_bufferPtr++;
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}
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// Search for an early sync to indicate an LDU following a header
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if (m_bufferPtr >= (P25_HDR_FRAME_LENGTH_BITS + P25_SYNC_LENGTH_BITS - 1U) && m_bufferPtr <= (P25_HDR_FRAME_LENGTH_BITS + P25_SYNC_LENGTH_BITS + 1U)) {
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// Fuzzy matching of the data sync bit sequence
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if (countBits64((m_bitBuffer & P25_SYNC_BITS_MASK) ^ P25_SYNC_BITS) <= SYNC_BIT_RUN_ERRS) {
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DEBUG2("P25RX: found LDU sync in Data, pos", m_bufferPtr - P25_SYNC_LENGTH_BITS);
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m_outBuffer[0U] = 0x01U;
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serial.writeP25Hdr(m_outBuffer, P25_HDR_FRAME_LENGTH_BYTES + 1U);
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// Restore the sync that's now in the wrong place
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for (uint8_t i = 0U; i < P25_SYNC_LENGTH_BYTES; i++)
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m_buffer[i] = P25_SYNC_BYTES[i];
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m_lostCount = MAX_SYNC_FRAMES;
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m_bufferPtr = P25_SYNC_LENGTH_BITS;
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}
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}
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// Only search for a sync in the right place +-2 symbols
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if (m_bufferPtr >= (P25_SYNC_LENGTH_BITS - 2U) && m_bufferPtr <= (P25_SYNC_LENGTH_BITS + 2U)) {
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// Fuzzy matching of the data sync bit sequence
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if (countBits64((m_bitBuffer & P25_SYNC_BITS_MASK) ^ P25_SYNC_BITS) <= SYNC_BIT_RUN_ERRS) {
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DEBUG2("P25RX: found sync in Data, pos", m_bufferPtr - P25_SYNC_LENGTH_BITS);
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m_lostCount = MAX_SYNC_FRAMES;
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m_bufferPtr = P25_SYNC_LENGTH_BITS;
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}
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}
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// Send a data frame to the host if the required number of bits have been received
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if (m_bufferPtr == P25_LDU_FRAME_LENGTH_BITS) {
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// We've not seen a data sync for too long, signal RXLOST and change to RX_NONE
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m_lostCount--;
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if (m_lostCount == 0U) {
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DEBUG1("P25RX: sync timed out, lost lock");
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io.setDecode(false);
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io.setADCDetection(false);
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serial.writeP25Lost();
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m_state = P25RXS_NONE;
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} else {
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m_outBuffer[0U] = m_lostCount == (MAX_SYNC_FRAMES - 1U) ? 0x01U : 0x00U;
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serial.writeP25Ldu(m_outBuffer, P25_LDU_FRAME_LENGTH_BYTES + 1U);
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// Start the next frame
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::memset(m_outBuffer, 0x00U, P25_LDU_FRAME_LENGTH_BYTES + 3U);
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m_bufferPtr = 0U;
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}
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}
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}
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