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* 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 "M17RX.h"

#include "Utils.h"

#include <stdio.h>

const uint8_t MAX_SYNC_BIT_START_ERRS = 0U;

const uint8_t MAX_SYNC_BIT_RUN_ERRS = 2U;

const unsigned int MAX_SYNC_FRAMES = 3U + 1U;

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])

CM17RX::CM17RX() :

m_state(M17RXS_NONE),

m_bitBuffer(0x00U),

m_outBuffer(),

m_buffer(NULL),

m_bufferPtr(0U),

m_lostCount(0U)

{

m_buffer = m_outBuffer + 1U;

}

void CM17RX::reset()

{

m_state = M17RXS_NONE;

m_bitBuffer = 0x00U;

m_bufferPtr = 0U;

m_lostCount = 0U;

}

void CM17RX::databit(bool bit)

{

switch (m_state) {

case M17RXS_LINK_SETUP:

case M17RXS_STREAM:

case M17RXS_PACKET:

processData(bit);

break;

default:

processNone(bit);

break;

}

void CM17RX::processNone(bool bit)

{

m_bitBuffer <<= 1;

if (bit)

m_bitBuffer |= 0x01U;

// Exact matching of the packet sync bit sequence

if (countBits16(m_bitBuffer ^ M17_PACKET_SYNC_BITS) <= MAX_SYNC_BIT_START_ERRS) {

DEBUG1("M17RX: packet sync found in None");

for (uint8_t i = 0U; i < M17_SYNC_BYTES_LENGTH; i++)

m_buffer[i] = M17_PACKET_SYNC_BYTES[i];

m_lostCount = MAX_SYNC_FRAMES;

m_bufferPtr = M17_SYNC_LENGTH_BITS;

m_state = M17RXS_PACKET;

io.setDecode(true);

return;

}

// Exact matching of the link setup sync bit sequence

if (countBits16(m_bitBuffer ^ M17_LINK_SETUP_SYNC_BITS) <= MAX_SYNC_BIT_START_ERRS) {

DEBUG1("M17RX: link setup sync found in None");

for (uint8_t i = 0U; i < M17_SYNC_BYTES_LENGTH; i++)

m_buffer[i] = M17_LINK_SETUP_SYNC_BYTES[i];

m_lostCount = MAX_SYNC_FRAMES;

m_bufferPtr = M17_SYNC_LENGTH_BITS;

m_state = M17RXS_LINK_SETUP;

io.setDecode(true);

return;

}

// Exact matching of the stream sync bit sequence

if (countBits16(m_bitBuffer ^ M17_STREAM_SYNC_BITS) <= MAX_SYNC_BIT_START_ERRS) {

DEBUG1("M17RX: stream sync found in None");

for (uint8_t i = 0U; i < M17_SYNC_BYTES_LENGTH; i++)

m_buffer[i] = M17_STREAM_SYNC_BYTES[i];

m_lostCount = MAX_SYNC_FRAMES;

m_bufferPtr = M17_SYNC_LENGTH_BITS;

m_state = M17RXS_STREAM;

io.setDecode(true);

return;

}

void CM17RX::processData(bool bit)

{

m_bitBuffer <<= 1;

if (bit)

m_bitBuffer |= 0x01U;

WRITE_BIT1(m_buffer, m_bufferPtr, bit);

m_bufferPtr++;

if (m_bufferPtr > M17_FRAME_LENGTH_BITS)

reset();

// Only search for the syncs in the right place +-1 bit

if (m_bufferPtr >= (M17_SYNC_LENGTH_BITS - 1U) && m_bufferPtr <= (M17_SYNC_LENGTH_BITS + 1U)) {

// Fuzzy matching of the packet sync bit sequence

if (countBits16(m_bitBuffer ^ M17_PACKET_SYNC_BITS) <= MAX_SYNC_BIT_RUN_ERRS) {

DEBUG2("M17RX: found packet sync, pos", m_bufferPtr - M17_SYNC_LENGTH_BITS);

m_lostCount = MAX_SYNC_FRAMES;

m_bufferPtr = M17_SYNC_LENGTH_BITS;

m_state = M17RXS_PACKET;

return;

}

// Fuzzy matching of the link setup sync bit sequence

if (countBits16(m_bitBuffer ^ M17_LINK_SETUP_SYNC_BITS) <= MAX_SYNC_BIT_RUN_ERRS) {

DEBUG2("M17RX: found link setup sync, pos", m_bufferPtr - M17_SYNC_LENGTH_BITS);

m_lostCount = MAX_SYNC_FRAMES;

m_bufferPtr = M17_SYNC_LENGTH_BITS;

m_state = M17RXS_LINK_SETUP;

return;

}

// Fuzzy matching of the stream sync bit sequence

if (countBits16(m_bitBuffer ^ M17_STREAM_SYNC_BITS) <= MAX_SYNC_BIT_RUN_ERRS) {

DEBUG2("M17RX: found stream sync, pos", m_bufferPtr - M17_SYNC_LENGTH_BITS);

m_lostCount = MAX_SYNC_FRAMES;

m_bufferPtr = M17_SYNC_LENGTH_BITS;

m_state = M17RXS_STREAM;

return;

}

// Fuzzy matching of the packet sync bit sequence

if (countBits16(m_bitBuffer ^ M17_PACKET_SYNC_BITS) <= MAX_SYNC_BIT_RUN_ERRS) {

DEBUG2("M17RX: found packet sync, pos", m_bufferPtr - M17_SYNC_LENGTH_BITS);

m_lostCount = MAX_SYNC_FRAMES;

m_bufferPtr = M17_SYNC_LENGTH_BITS;

m_state = M17RXS_PACKET;

return;

}

// Fuzzy matching of the EOT sync bit sequence

if (countBits16(m_bitBuffer ^ M17_EOT_SYNC_BITS) <= MAX_SYNC_BIT_RUN_ERRS) {

DEBUG2("M17RX: found eot sync, pos", m_bufferPtr - M17_SYNC_LENGTH_BITS);

io.setDecode(false);

serial.writeM17EOT();

reset();

return;

}

// Send a frame to the host if the required number of bits have been received

if (m_bufferPtr == M17_FRAME_LENGTH_BITS) {

// We've not seen a sync for too long, signal RXLOST and change to RX_NONE

m_lostCount--;

if (m_lostCount == 0U) {

DEBUG1("M17RX: sync timed out, lost lock");

io.setDecode(false);

serial.writeM17Lost();

reset();

} else {

// Write data to host

m_outBuffer[0U] = m_lostCount == (MAX_SYNC_FRAMES - 1U) ? 0x01U : 0x00U;

switch (m_state) {

case M17RXS_LINK_SETUP:

writeRSSILinkSetup(m_outBuffer);

break;

case M17RXS_STREAM:

writeRSSIStream(m_outBuffer);

break;

case M17RXS_PACKET:

writeRSSIPacket(m_outBuffer);

break;

default:

break;

}

// Start the next frame

::memset(m_outBuffer, 0x00U, M17_FRAME_LENGTH_BYTES + 3U);

m_bufferPtr = 0U;

}

void CM17RX::writeRSSILinkSetup(uint8_t* data)

{

#if defined(SEND_RSSI_DATA)

uint16_t rssi = io.readRSSI();

data[49U] = (rssi >> 8) & 0xFFU;

data[50U] = (rssi >> 0) & 0xFFU;

serial.writeM17LinkSetup(data, M17_FRAME_LENGTH_BYTES + 3U);

#else

serial.writeM17LinkSetup(data, M17_FRAME_LENGTH_BYTES + 1U);

#endif

}

void CM17RX::writeRSSIStream(uint8_t* data)

{

#if defined(SEND_RSSI_DATA)

uint16_t rssi = io.readRSSI();

data[49U] = (rssi >> 8) & 0xFFU;

data[50U] = (rssi >> 0) & 0xFFU;

serial.writeM17Stream(data, M17_FRAME_LENGTH_BYTES + 3U);

#else

serial.writeM17Stream(data, M17_FRAME_LENGTH_BYTES + 1U);

#endif

}

void CM17RX::writeRSSIPacket(uint8_t* data)

{

#if defined(SEND_RSSI_DATA)

uint16_t rssi = io.readRSSI();

data[49U] = (rssi >> 8) & 0xFFU;

data[50U] = (rssi >> 0) & 0xFFU;

serial.writeM17Packet(data, M17_FRAME_LENGTH_BYTES + 3U);

#else

serial.writeM17Packet(data, M17_FRAME_LENGTH_BYTES + 1U);

#endif

}

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