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/*
* Copyright (C) 2016 by Daniel Friesel
*
* License: You may use, redistribute and/or modify this file under the terms
* of either:
* * The GNU LGPL v3 (see COPYING and COPYING.LESSER), or
* * The 3-clause BSD License (see COPYING.BSD)
*
*/
#include <avr/io.h>
#include <stdlib.h>
#ifndef FECMODEM_H_
#define FECMODEM_H_
#include "hamming.h"
#include "modem.h"
/**
* Receive-only modem with forward error correction.
* Uses the Modem class to read raw modem data and uses the Hamming 2416
* algorithm to detect and, if possible, correct transmission errors.
* Exposes a global modem object for convenience.
*/
class FECModem : public Modem {
private:
enum HammingState : uint8_t {
FIRST_BYTE,
SECOND_BYTE
};
HammingState hammingState;
uint8_t buf_byte;
uint8_t parity128(uint8_t byte);
uint8_t parity2416(uint8_t byte1, uint8_t byte2);
uint8_t correct128(uint8_t *byte, uint8_t parity);
uint8_t hamming2416(uint8_t *byte1, uint8_t *byte2, uint8_t parity);
public:
FECModem() : Modem() {};
/**
* Enable the modem. Resets the internal Hamming state and calls
* Modem::enable().
*/
void enable(void);
/**
* Checks if there are unprocessed bytes in the receive buffer.
* Parity bytes are accounted for, so if three raw bytes (two data,
* one parity) were received by Modem::receive(), this function will
* return 2.
* @return number of unprocessed data bytes
*/
uint8_t buffer_available(void);
/**
* Get next byte from the receive buffer.
* @return received byte (0 if it contained uncorrectable errors
* or the buffer is empty)
*/
uint8_t buffer_get(void);
};
extern FECModem modem;
#endif /* FECMODEM_H_ */
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