ft8_lib/ft8/v1/encode.h

#pragma once

#include <stdint.h>

constexpr int ND = 58;      // Data symbols
constexpr int NS = 21;      // Sync symbols (3 @ Costas 7x7)
constexpr int NN = NS+ND;   // Total channel symbols (79)


// Generate FT8 tone sequence from payload data
// [IN] payload - 9 byte array consisting of 72 bit payload
// [IN] i3      - 3 bits containing message type (zero?)
// [OUT] itone  - array of NN (79) bytes to store the generated tones (encoded as 0..7)
void genft8(const uint8_t *payload, uint8_t i3, uint8_t *itone);


// Encode an 87-bit message and return a 174-bit codeword. 
// The generator matrix has dimensions (87,87). 
// The code is a (174,87) regular ldpc code with column weight 3.
// The code was generated using the PEG algorithm.
// After creating the codeword, the columns are re-ordered according to 
// "colorder" to make the codeword compatible with the parity-check matrix 
// Arguments:
//   * message - array of 87 bits stored as 11 bytes (MSB first)
//   * codeword - array of 174 bits stored as 22 bytes (MSB first)
void encode174(const uint8_t *message, uint8_t *codeword);

// Compute 12-bit CRC for a sequence of given number of bits
// [IN] message  - byte sequence (MSB first)
// [IN] num_bits - number of bits in the sequence
uint16_t ft8_crc(uint8_t *message, int num_bits);