kopia lustrzana https://github.com/F5OEO/ft8_lib
Extra comments and minor updates
Karlis Goba
rodzic
5aa5bd077c
commit
2da7757586
2
Makefile
2
Makefile
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@ -1,5 +1,5 @@
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CXXFLAGS = -std=c++14
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LDFLAGS = -lm
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test: test.o encode.o pack.o
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gen_ft8: gen_ft8.o encode.o pack.o
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$(CXX) $(LDFLAGS) -o $@ $^
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35
encode.cpp
35
encode.cpp
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@ -1,11 +1,11 @@
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#include "encode.h"
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constexpr int N = 174, K = 87, M = N-K;
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constexpr int N = 174, K = 87, M = N-K; // Define the LDPC sizes
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constexpr uint16_t POLYNOMIAL = 0xC06; // CRC-12 polynomial without the leading (MSB) 1
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// Parity generator matrix for (174,87) code, stored in bitpacked format (MSB first)
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constexpr uint8_t G[87][11] = {
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// Parity generator matrix for (174,87) LDPC code, stored in bitpacked format (MSB first)
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const uint8_t G[87][11] = {
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{ 0x23, 0xbb, 0xa8, 0x30, 0xe2, 0x3b, 0x6b, 0x6f, 0x50, 0x98, 0x2e },
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{ 0x1f, 0x8e, 0x55, 0xda, 0x21, 0x8c, 0x5d, 0xf3, 0x30, 0x90, 0x52 },
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{ 0xca, 0x7b, 0x32, 0x17, 0xcd, 0x92, 0xbd, 0x59, 0xa5, 0xae, 0x20 },
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@ -128,11 +128,9 @@ uint8_t parity8(uint8_t x) {
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// After creating the codeword, the columns are re-ordered according to
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// "colorder" to make the codeword compatible with the parity-check matrix
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// Arguments:
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// * message - array of 87 bits stored as 11 bytes (MSB first)
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// * codeword - array of 174 bits stored as 22 bytes (MSB first)
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// [IN] message - array of 87 bits stored as 11 bytes (MSB first)
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// [OUT] codeword - array of 174 bits stored as 22 bytes (MSB first)
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void encode174(const uint8_t *message, uint8_t *codeword) {
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static bool first = true;
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// Here we don't generate the generator bit matrix as in WSJT-X implementation
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// Instead we access the generator bits straight from the binary representation in G
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@ -186,18 +184,23 @@ void encode174(const uint8_t *message, uint8_t *codeword) {
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}
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uint16_t ft8_crc(uint8_t *message, int nBits) {
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const int WIDTH = 12;
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const uint16_t TOPBIT = (1 << (WIDTH - 1));
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// Compute 12-bit CRC for a sequence of given number of bits
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// [IN] message - byte sequence (MSB first)
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// [IN] num_bits - number of bits in the sequence
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uint16_t ft8_crc(uint8_t *message, int num_bits) {
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// Adapted from https://barrgroup.com/Embedded-Systems/How-To/CRC-Calculation-C-Code
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constexpr int WIDTH = 12;
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constexpr uint16_t TOPBIT = (1 << (WIDTH - 1));
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uint16_t remainder = 0;
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int iByte = 0;
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int idx_byte = 0;
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// Perform modulo-2 division, a bit at a time.
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for (int iBit = 0; iBit < nBits; ++iBit) {
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if (iBit % 8 == 0) {
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for (int idx_bit = 0; idx_bit < num_bits; ++idx_bit) {
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if (idx_bit % 8 == 0) {
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// Bring the next byte into the remainder.
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remainder ^= (message[iByte] << (WIDTH - 8));
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++iByte;
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remainder ^= (message[idx_byte] << (WIDTH - 8));
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++idx_byte;
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}
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// Try to divide the current data bit.
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@ -213,7 +216,7 @@ uint16_t ft8_crc(uint8_t *message, int nBits) {
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// Generate FT8 tone sequence from payload data
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// [IN] payload - 9 byte array consisting of 72 bit payload
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// [IN] payload - 9 byte array consisting of 72 bit payload (MSB first)
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// [IN] i3 - 3 bits containing message type (zero?)
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// [OUT] itone - array of NN (79) bytes to store the generated tones (encoded as 0..7)
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void genft8(const uint8_t *payload, uint8_t i3, uint8_t *itone) {
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@ -148,8 +148,22 @@ void test3() {
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}
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void usage() {
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printf("Generate a 15-second WAV file encoding a given message.\n");
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printf("Usage:\n");
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printf("\n");
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printf("gen_ft8 MESSAGE WAV_FILE\n");
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printf("\n");
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printf("(Note that you might have to enclose your message in quote marks if it contains spaces)\n");
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}
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int main(int argc, char **argv) {
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if (argc < 3) return -1;
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// Expect two command-line arguments
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if (argc < 3) {
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usage();
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return -1;
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}
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//const char *message = "G0UPL YL3JG 73";
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const char *message = argv[1];
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74
pack.cpp
74
pack.cpp
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@ -3,9 +3,13 @@
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#include "pack.h"
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constexpr int NBASE = 37*36*10*27*27*27;
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constexpr int NGBASE = 180*180;
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// Utility functions for characters and strings
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char to_upper(char c) {
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return (c >= 'a' && c <= 'z') ? (c - 'a' + 'A') : c;
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}
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@ -31,7 +35,7 @@ bool equals(const char *string1, const char *string2) {
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}
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// Message formatting:
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// Text message formatting:
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// - replaces lowercase letters with uppercase
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// - merges consecutive spaces into single space
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void fmtmsg(char *msg_out, const char *msg_in) {
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@ -50,9 +54,9 @@ void fmtmsg(char *msg_out, const char *msg_in) {
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// Returns integer encoding of a character (number/digit/space).
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// * Digits are encoded as 0..9
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// * Letters a..z are encoded as 10..35 (case insensitive)
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// * Space is encoded as 36
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// - Digits are encoded as 0..9
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// - Letters a..z are encoded as 10..35 (case insensitive)
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// - Space is encoded as 36
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uint8_t nchar(char c) {
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if (is_digit(c)) {
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return (c - '0');
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@ -87,7 +91,7 @@ void pack3_8bit(uint32_t nc1, uint32_t nc2, uint16_t ng, uint8_t *payload) {
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// Pack FT8 source/destination and grid data into 72 bits (stored as 12 bytes of 6-bit values)
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// (For compatibility with WSJT-X and testing)
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// (Unused here, included for compatibility with WSJT-X and testing)
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// [IN] nc1 - first callsign data (28 bits)
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// [IN] nc2 - second callsign data (28 bits)
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// [IN] ng - grid data (16 bits)
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@ -115,11 +119,11 @@ int dd_to_int(const char *str, int length) {
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int i;
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if (str[0] == '-') {
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negative = true;
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i = 1;
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i = 1; // Consume the - sign
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}
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else {
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negative = false;
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i = (str[0] == '+') ? 1 : 0;
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i = (str[0] == '+') ? 1 : 0; // Consume a + sign if found
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}
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while (i < length) {
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@ -134,15 +138,16 @@ int dd_to_int(const char *str, int length) {
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}
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// Convert a 2 digit integer to string
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void int_to_dd(char *str, int value, int width) {
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if (value < 0) {
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*str = '-';
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str++;
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++str;
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value = -value;
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}
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int divisor = 1;
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for (int i = 0; i < width; i++) {
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for (int i = 0; i < width; ++i) {
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divisor *= 10;
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}
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@ -150,18 +155,18 @@ void int_to_dd(char *str, int value, int width) {
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int digit = value / divisor;
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*str = '0' + digit;
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str++;
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++str;
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value -= digit * divisor;
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divisor /= 10;
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}
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*str = 0;
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*str = 0; // Add zero terminator
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}
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// Pack a valid callsign into a 28-bit integer.
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int32_t packcall(const char *callsign) {
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printf("Callsign = [%s]\n", callsign);
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//LOG("Callsign = [%s]\n", callsign);
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if (equals(callsign, "CQ")) {
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// TODO: support 'CQ nnn' frequency specification
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//if (callsign(4:4).ge.'0' .and. callsign(4:4).le.'9' .and. &
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@ -241,13 +246,14 @@ int32_t packcall(const char *callsign) {
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// Pack a valid grid locator into an integer.
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int16_t packgrid(const char *grid) {
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printf("Grid = [%s]\n", grid);
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//LOG("Grid = [%s]\n", grid);
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int len = strlen(grid);
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if (len == 0) {
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// Blank grid is OK
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return NGBASE + 1;
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}
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// Check for RO, RRR, or 73 in the message field normally used for grid
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if (equals(grid, "RO")) {
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return NGBASE + 62;
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@ -259,7 +265,7 @@ int16_t packgrid(const char *grid) {
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return NGBASE + 64;
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}
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// TODO:
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// Attempt to parse signal reports (e.g. "-07", "R+20")
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char c1 = grid[0];
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int n;
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if (c1 == 'R') {
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@ -282,7 +288,7 @@ int16_t packgrid(const char *grid) {
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char grid4[4];
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memcpy(grid4, grid, 4);
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// Check for extended-range signal reports: -50 to -31, and 0 to +49
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// TODO: Check for extended-range signal reports: -50 to -31, and 0 to +49
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// if (n >= -50 && n <= 49) {
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// if (c1 == 'R') {
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// // write(grid,1002) n+50 1002 format('LA',i2.2)
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@ -297,14 +303,14 @@ int16_t packgrid(const char *grid) {
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// return -1;
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// }
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// Check the locator
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// Check if the grid locator is properly formatted
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if (len != 4) return -1;
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if (grid4[0] < 'A' || grid4[0] > 'R') return -1;
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if (grid4[1] < 'A' || grid4[1] > 'R') return -1;
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if (grid4[2] < '0' || grid4[2] > '9') return -1;
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if (grid4[3] < '0' || grid4[3] > '9') return -1;
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// OK, we have a properly formatted grid locator
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// Extract latitude and longitude
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int lng = (grid4[0] - 'A') * 20;
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lng += (grid4[2] - '0') * 2;
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lng = 179 - lng;
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@ -313,6 +319,7 @@ int16_t packgrid(const char *grid) {
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lat += (grid4[3] - '0') * 1;
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lat -= 90;
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// Convert latitude and longitude into single number
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int16_t ng = (lng + 180) / 2;
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ng *= 180;
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ng += lat + 90;
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@ -322,16 +329,16 @@ int16_t packgrid(const char *grid) {
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int packmsg(const char *msg, uint8_t *dat) { // , itype, bcontest
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// TODO: maximum allowed length?
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if (strlen(msg) > 18) {
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// TODO: check what is maximum allowed length?
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if (strlen(msg) > 22) {
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return -1;
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}
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char msg2[19]; // Including zero terminator!
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char msg2[23]; // Including zero terminator!
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fmtmsg(msg2, msg);
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//printf("msg2 = [%s]\n", msg2);
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//LOG("msg2 = [%s]\n", msg2);
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// TODO: Change 'CQ n ' type messages to 'CQ 00n '
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//if(msg(1:3).eq.'CQ ' .and. msg(4:4).ge.'0' .and. msg(4:4).le.'9' &
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@ -355,16 +362,19 @@ int packmsg(const char *msg, uint8_t *dat) { // , itype, bcontest
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}
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}
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// Locate the first space in the message and replace it with zero terminator
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// Try to split the message into three space-delimited fields
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// by locating spaces and changing them to zero terminators
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// Locate the first delimiter in the message
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char *s1 = strchr(msg2, ' ');
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if (s1 == NULL) {
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// TODO: handle this (plain text message?)
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return -2;
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}
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*s1 = 0;
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++s1;
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*s1 = 0; // Separate fields by zero terminator
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++s1; // Now s1 points to the second field
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// Locate the second space in the message
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// Locate the second delimiter in the message
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char *s2 = strchr(s1 + 1, ' ');
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if (s2 == NULL) {
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// If the second space is not found, point to the end of string
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@ -372,17 +382,17 @@ int packmsg(const char *msg, uint8_t *dat) { // , itype, bcontest
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s2 = msg2 + strlen(msg2);
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}
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else {
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*s2 = 0;
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++s2;
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*s2 = 0;// Separate fields by zero terminator
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++s2; // Now s2 points to the third field
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}
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// TODO: process callsign prefixes/suffixes
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// Pack message fields into integers
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int nc1 = packcall(msg2);
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int nc2 = packcall(s1);
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int ng = packgrid(s2);
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// TODO: callsign prefixes/suffixes
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// TODO: plain text messages
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//call packtext(msg,nc1,nc2,ng)
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//ng=ng+32768
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@ -390,12 +400,12 @@ int packmsg(const char *msg, uint8_t *dat) { // , itype, bcontest
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if (nc1 < 0 || nc2 < 0 || ng < 0) {
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return -3;
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}
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//printf("nc1 = %d [%04X], nc2 = %d [%04X], ng = %d\n", nc1, nc1, nc2, nc2, ng);
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//LOG("nc1 = %d [%04X], nc2 = %d [%04X], ng = %d\n", nc1, nc1, nc2, nc2, ng);
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// Originally the data was packed in bytes of 6 bits.
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// This seems to waste memory unnecessary and complicate the code, so we pack it in 8 bit values.
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pack3_8bit(nc1, nc2, ng, dat);
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//pack3_6bit(nc1, nc2, ng, dat);
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return 0;
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return 0; // Success!
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}
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