blob: c9a942b0447e02c5463f81d80cde5ebc208ae1dd (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
|
#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() { hammingState = FIRST_BYTE; };
/**
* 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_ */
|
