mirror of
https://github.com/f4exb/sdrangel.git
synced 2024-12-25 04:03:30 -05:00
358 lines
12 KiB
C++
358 lines
12 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
|
|
// Copyright (C) 2020 Edouard Griffiths, F4EXB //
|
|
// //
|
|
// Inspired by: https://github.com/myriadrf/LoRa-SDR //
|
|
// //
|
|
// 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 as version 3 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 V3 for more details. //
|
|
// //
|
|
// You should have received a copy of the GNU General Public License //
|
|
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
|
|
///////////////////////////////////////////////////////////////////////////////////
|
|
|
|
#ifndef INCLUDE_CHIRPCHATDEMODDECODERLORA_H
|
|
#define INCLUDE_CHIRPCHATDEMODDECODERLORA_H
|
|
|
|
#include <vector>
|
|
#include <QByteArray>
|
|
|
|
class ChirpChatDemodDecoderLoRa
|
|
{
|
|
public:
|
|
enum ParityStatus
|
|
{
|
|
ParityUndefined,
|
|
ParityError,
|
|
ParityCorrected,
|
|
ParityOK
|
|
};
|
|
|
|
static void decodeBytes(
|
|
QByteArray& bytes,
|
|
const std::vector<unsigned short>& inSymbols,
|
|
unsigned int nbSymbolBits,
|
|
bool hasHeader,
|
|
bool& hasCRC,
|
|
unsigned int& nbParityBits,
|
|
unsigned int& packetLength,
|
|
bool& earlyEOM,
|
|
int& headerParityStatus,
|
|
bool& headerCRCStatus,
|
|
int& payloadParityStatus,
|
|
bool& payloadCRCStatus
|
|
);
|
|
|
|
static void getCodingMetrics(
|
|
unsigned int nbSymbolBits,
|
|
unsigned int nbParityBits,
|
|
unsigned int packetLength,
|
|
bool hasHeader,
|
|
bool hasCRC,
|
|
unsigned int& numSymbols,
|
|
unsigned int& numCodewords
|
|
);
|
|
|
|
private:
|
|
static void decodeHeader(
|
|
const std::vector<unsigned short>& inSymbols,
|
|
unsigned int nbSymbolBits,
|
|
bool& hasCRC,
|
|
unsigned int& nbParityBits,
|
|
unsigned int& packetLength,
|
|
int& headerParityStatus,
|
|
bool& headerCRCStatus
|
|
);
|
|
|
|
static const unsigned int headerParityBits = 4;
|
|
static const unsigned int headerSymbols = 8;
|
|
static const unsigned int headerCodewords = 5;
|
|
|
|
/***********************************************************************
|
|
* Round functions
|
|
**********************************************************************/
|
|
static inline unsigned roundUp(unsigned num, unsigned factor)
|
|
{
|
|
return ((num + factor - 1) / factor) * factor;
|
|
}
|
|
|
|
/***********************************************************************
|
|
* https://en.wikipedia.org/wiki/Gray_code
|
|
**********************************************************************/
|
|
|
|
/*
|
|
* This function converts an unsigned binary
|
|
* number to reflected binary Gray code.
|
|
*
|
|
* The operator >> is shift right. The operator ^ is exclusive or.
|
|
*/
|
|
static inline unsigned short binaryToGray16(unsigned short num)
|
|
{
|
|
return num ^ (num >> 1);
|
|
}
|
|
|
|
/***********************************************************************
|
|
* Diagonal deinterleaver
|
|
**********************************************************************/
|
|
static inline void diagonalDeinterleaveSx(
|
|
const uint16_t *symbols,
|
|
const unsigned int numSymbols,
|
|
uint8_t *codewords,
|
|
const unsigned int nbSymbolBits,
|
|
const unsigned int nbParityBits)
|
|
{
|
|
for (unsigned int x = 0; x < numSymbols / (4 + nbParityBits); x++)
|
|
{
|
|
const unsigned int cwOff = x*nbSymbolBits;
|
|
const unsigned int symOff = x*(4 + nbParityBits);
|
|
|
|
for (unsigned int k = 0; k < 4 + nbParityBits; k++)
|
|
{
|
|
for (unsigned int m = 0; m < nbSymbolBits; m++)
|
|
{
|
|
const unsigned int i = (m + k) % nbSymbolBits;
|
|
const auto bit = (symbols[symOff + k] >> m) & 0x1;
|
|
codewords[cwOff + i] |= (bit << k);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/***********************************************************************
|
|
* Whitening generator reverse engineered from Sx1272 data stream.
|
|
* Same as above but using the actual interleaved LFSRs.
|
|
**********************************************************************/
|
|
static inline void Sx1272ComputeWhiteningLfsr(uint8_t *buffer, uint16_t bufferSize, const int bitOfs, const unsigned int nbParityBits)
|
|
{
|
|
static const uint64_t seed1[2] = {0x6572D100E85C2EFF,0xE85C2EFFFFFFFFFF}; // lfsr start values
|
|
static const uint64_t seed2[2] = {0x05121100F8ECFEEF,0xF8ECFEEFEFEFEFEF}; // lfsr start values for single parity mode (1 == nbParityBits)
|
|
const uint8_t m = 0xff >> (4 - nbParityBits);
|
|
uint64_t r[2] = {(1 == nbParityBits)?seed2[0]:seed1[0],(1 == nbParityBits)?seed2[1]:seed1[1]};
|
|
int i,j;
|
|
|
|
for (i = 0; i < bitOfs;i++)
|
|
{
|
|
r[i & 1] = (r[i & 1] >> 8) | (((r[i & 1] >> 32) ^ (r[i & 1] >> 24) ^ (r[i & 1] >> 16) ^ r[i & 1]) << 56); // poly: 0x1D
|
|
}
|
|
|
|
for (j = 0; j < bufferSize; j++,i++)
|
|
{
|
|
buffer[j] ^= r[i & 1] & m;
|
|
r[i & 1] = (r[i & 1] >> 8) | (((r[i & 1] >> 32) ^ (r[i & 1] >> 24) ^ (r[i & 1] >> 16) ^ r[i & 1]) << 56);
|
|
}
|
|
}
|
|
|
|
/***********************************************************************
|
|
* Decode 8 bits into a 4 bit word with single bit correction.
|
|
* Non standard version used in sx1272.
|
|
* Set error to true when a parity error was detected
|
|
* Set bad to true when the result could not be corrected
|
|
**********************************************************************/
|
|
static inline unsigned char decodeHamming84sx(const unsigned char b, bool &error, bool &bad)
|
|
{
|
|
auto b0 = (b >> 0) & 0x1;
|
|
auto b1 = (b >> 1) & 0x1;
|
|
auto b2 = (b >> 2) & 0x1;
|
|
auto b3 = (b >> 3) & 0x1;
|
|
auto b4 = (b >> 4) & 0x1;
|
|
auto b5 = (b >> 5) & 0x1;
|
|
auto b6 = (b >> 6) & 0x1;
|
|
auto b7 = (b >> 7) & 0x1;
|
|
|
|
auto p0 = (b0 ^ b1 ^ b2 ^ b4);
|
|
auto p1 = (b1 ^ b2 ^ b3 ^ b5);
|
|
auto p2 = (b0 ^ b1 ^ b3 ^ b6);
|
|
auto p3 = (b0 ^ b2 ^ b3 ^ b7);
|
|
|
|
auto parity = (p0 << 0) | (p1 << 1) | (p2 << 2) | (p3 << 3);
|
|
if (parity != 0) error = true;
|
|
switch (parity & 0xf)
|
|
{
|
|
case 0xD: return (b ^ 1) & 0xf;
|
|
case 0x7: return (b ^ 2) & 0xf;
|
|
case 0xB: return (b ^ 4) & 0xf;
|
|
case 0xE: return (b ^ 8) & 0xf;
|
|
case 0x0:
|
|
case 0x1:
|
|
case 0x2:
|
|
case 0x4:
|
|
case 0x8: return b & 0xf;
|
|
default: bad = true; return b & 0xf;
|
|
}
|
|
}
|
|
|
|
/***********************************************************************
|
|
* Simple 8-bit checksum routine
|
|
**********************************************************************/
|
|
static inline uint8_t checksum8(const uint8_t *p, const size_t len)
|
|
{
|
|
uint8_t acc = 0;
|
|
|
|
for (size_t i = 0; i < len; i++)
|
|
{
|
|
acc = (acc >> 1) + ((acc & 0x1) << 7); //rotate
|
|
acc += p[i]; //add
|
|
}
|
|
|
|
return acc;
|
|
}
|
|
|
|
static inline uint8_t headerChecksum(const uint8_t *h)
|
|
{
|
|
auto a0 = (h[0] >> 4) & 0x1;
|
|
auto a1 = (h[0] >> 5) & 0x1;
|
|
auto a2 = (h[0] >> 6) & 0x1;
|
|
auto a3 = (h[0] >> 7) & 0x1;
|
|
|
|
auto b0 = (h[0] >> 0) & 0x1;
|
|
auto b1 = (h[0] >> 1) & 0x1;
|
|
auto b2 = (h[0] >> 2) & 0x1;
|
|
auto b3 = (h[0] >> 3) & 0x1;
|
|
|
|
auto c0 = (h[1] >> 0) & 0x1;
|
|
auto c1 = (h[1] >> 1) & 0x1;
|
|
auto c2 = (h[1] >> 2) & 0x1;
|
|
auto c3 = (h[1] >> 3) & 0x1;
|
|
|
|
uint8_t res;
|
|
res = (a0 ^ a1 ^ a2 ^ a3) << 4;
|
|
res |= (a3 ^ b1 ^ b2 ^ b3 ^ c0) << 3;
|
|
res |= (a2 ^ b0 ^ b3 ^ c1 ^ c3) << 2;
|
|
res |= (a1 ^ b0 ^ b2 ^ c0 ^ c1 ^ c2) << 1;
|
|
res |= a0 ^ b1 ^ c0 ^ c1 ^ c2 ^ c3;
|
|
|
|
return res;
|
|
}
|
|
|
|
/***********************************************************************
|
|
* Check parity for 5/4 code.
|
|
* return true if parity is valid.
|
|
**********************************************************************/
|
|
static inline unsigned char checkParity54(const unsigned char b, bool &error)
|
|
{
|
|
auto x = b ^ (b >> 2);
|
|
x = x ^ (x >> 1) ^ (b >> 4);
|
|
|
|
if (x & 1) {
|
|
error = true;
|
|
}
|
|
|
|
return b & 0xf;
|
|
}
|
|
|
|
/***********************************************************************
|
|
* Check parity for 6/4 code.
|
|
* return true if parity is valid.
|
|
**********************************************************************/
|
|
static inline unsigned char checkParity64(const unsigned char b, bool &error)
|
|
{
|
|
auto x = b ^ (b >> 1) ^ (b >> 2);
|
|
auto y = x ^ b ^ (b >> 3);
|
|
x ^= b >> 4;
|
|
y ^= b >> 5;
|
|
|
|
if ((x | y) & 1) {
|
|
error = true;
|
|
}
|
|
|
|
return b & 0xf;
|
|
}
|
|
|
|
/***********************************************************************
|
|
* Decode 7 bits into a 4 bit word with single bit correction.
|
|
* Non standard version used in sx1272.
|
|
* Set error to true when a parity error was detected
|
|
* Non correctable errors are indistinguishable from single or no errors
|
|
* therefore no 'bad' variable is proposed
|
|
**********************************************************************/
|
|
static inline unsigned char decodeHamming74sx(const unsigned char b, bool &error)
|
|
{
|
|
auto b0 = (b >> 0) & 0x1;
|
|
auto b1 = (b >> 1) & 0x1;
|
|
auto b2 = (b >> 2) & 0x1;
|
|
auto b3 = (b >> 3) & 0x1;
|
|
auto b4 = (b >> 4) & 0x1;
|
|
auto b5 = (b >> 5) & 0x1;
|
|
auto b6 = (b >> 6) & 0x1;
|
|
|
|
auto p0 = (b0 ^ b1 ^ b2 ^ b4);
|
|
auto p1 = (b1 ^ b2 ^ b3 ^ b5);
|
|
auto p2 = (b0 ^ b1 ^ b3 ^ b6);
|
|
|
|
auto parity = (p0 << 0) | (p1 << 1) | (p2 << 2);
|
|
|
|
if (parity != 0) {
|
|
error = true;
|
|
}
|
|
|
|
switch (parity)
|
|
{
|
|
case 0x5: return (b ^ 1) & 0xf;
|
|
case 0x7: return (b ^ 2) & 0xf;
|
|
case 0x3: return (b ^ 4) & 0xf;
|
|
case 0x6: return (b ^ 8) & 0xf;
|
|
case 0x0:
|
|
case 0x1:
|
|
case 0x2:
|
|
case 0x4: break;
|
|
}
|
|
|
|
return b & 0xf;
|
|
}
|
|
|
|
/***********************************************************************
|
|
* CRC reverse engineered from Sx1272 data stream.
|
|
* Modified CCITT crc with masking of the output with an 8bit lfsr
|
|
**********************************************************************/
|
|
static inline uint16_t crc16sx(uint16_t crc, const uint16_t poly)
|
|
{
|
|
for (int i = 0; i < 8; i++)
|
|
{
|
|
if (crc & 0x8000) {
|
|
crc = (crc << 1) ^ poly;
|
|
} else {
|
|
crc <<= 1;
|
|
}
|
|
}
|
|
|
|
return crc;
|
|
}
|
|
|
|
static inline uint8_t xsum8(uint8_t t)
|
|
{
|
|
t ^= t >> 4;
|
|
t ^= t >> 2;
|
|
t ^= t >> 1;
|
|
|
|
return (t & 1);
|
|
}
|
|
|
|
static inline uint16_t sx1272DataChecksum(const uint8_t *data, int length)
|
|
{
|
|
uint16_t res = 0;
|
|
uint8_t v = 0xff;
|
|
uint16_t crc = 0;
|
|
|
|
for (int i = 0; i < length; i++)
|
|
{
|
|
crc = crc16sx(res, 0x1021);
|
|
v = xsum8(v & 0xB8) | (v << 1);
|
|
res = crc ^ data[i];
|
|
}
|
|
|
|
res ^= v;
|
|
v = xsum8(v & 0xB8) | (v << 1);
|
|
res ^= v << 8;
|
|
|
|
return res;
|
|
}
|
|
};
|
|
|
|
#endif // INCLUDE_CHIRPCHATDEMODDECODERLORA_H
|