diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/fecmodem.cc | 49 | ||||
| -rw-r--r-- | src/fecmodem.h | 20 | ||||
| -rw-r--r-- | src/hamming.h | 37 | ||||
| -rw-r--r-- | src/main.cc | 2 | ||||
| -rw-r--r-- | src/modem.cc | 5 | ||||
| -rw-r--r-- | src/modem.h | 2 | ||||
| -rw-r--r-- | src/system.cc | 2 |
7 files changed, 111 insertions, 6 deletions
diff --git a/src/fecmodem.cc b/src/fecmodem.cc new file mode 100644 index 0000000..5323135 --- /dev/null +++ b/src/fecmodem.cc @@ -0,0 +1,49 @@ +#include <avr/io.h> +#include <stdlib.h> +#include "fecmodem.h" + +uint8_t FECModem::parity128(uint8_t byte) +{ + return pgm_read_byte(&hammingParityLow[byte & 0x0f]) ^ pgm_read_byte(&hammingParityHigh[byte >> 4]); +} + +uint8_t FECModem::parity2416(uint8_t byte1, uint8_t byte2) +{ + return parity128(byte1) | (parity128(byte2) << 4); +} + +uint8_t FECModem::correct128(uint8_t *byte, uint8_t err) +{ + uint8_t result = pgm_read_byte(&hammingParityCheck[err & 0x0f]); + + if (result != NO_ERROR) { + if (result == UNCORRECTABLE || byte == NULL) { + return 3; + } else { + if (result != ERROR_IN_PARITY) { + *byte ^= result; + } + return 1; + } + } + return 0; +} + +uint8_t FECModem::hamming2416(uint8_t *byte1, uint8_t *byte2, uint8_t parity) +{ + uint8_t err; + + if (byte1 == NULL || byte2 == NULL) { + return 3; + } + + err = parity2416(*byte1, *byte2) ^ parity; + + if (err) { + return correct128(byte1, err) + correct128(byte2, err >> 4); + } + + return 0; +} + +FECModem modem; diff --git a/src/fecmodem.h b/src/fecmodem.h new file mode 100644 index 0000000..dd36f68 --- /dev/null +++ b/src/fecmodem.h @@ -0,0 +1,20 @@ +#include <avr/io.h> +#include <stdlib.h> + +#ifndef FECMODEM_H_ +#define FECMODEM_H_ + +#include "hamming.h" +#include "modem.h" + +class FECModem : public Modem { + private: + 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); +}; + +extern FECModem modem; + +#endif /* FECMODEM_H_ */ diff --git a/src/hamming.h b/src/hamming.h new file mode 100644 index 0000000..9828baa --- /dev/null +++ b/src/hamming.h @@ -0,0 +1,37 @@ +#ifndef HAMMING_H_ +#define HAMMING_H_ + +#include <avr/pgmspace.h> + +enum HammingResult : uint8_t { + NO_ERROR = 0, + ERROR_IN_PARITY = 0xfe, + UNCORRECTABLE = 0xff, +}; + +const uint8_t hammingParityLow[] PROGMEM = +{ 0, 3, 5, 6, 6, 5, 3, 0, 7, 4, 2, 1, 1, 2, 4, 7 }; + +const uint8_t hammingParityHigh[] PROGMEM = +{ 0, 9, 10, 3, 11, 2, 1, 8, 12, 5, 6, 15, 7, 14, 13, 4 }; + +const uint8_t PROGMEM hammingParityCheck[] = { + NO_ERROR, + ERROR_IN_PARITY, + ERROR_IN_PARITY, + 0x01, + ERROR_IN_PARITY, + 0x02, + 0x04, + 0x08, + ERROR_IN_PARITY, + 0x10, + 0x20, + 0x40, + 0x80, + UNCORRECTABLE, + UNCORRECTABLE, + UNCORRECTABLE +}; + +#endif /* HAMMING_H_ */ diff --git a/src/main.cc b/src/main.cc index 37dc8bd..ae9ebc5 100644 --- a/src/main.cc +++ b/src/main.cc @@ -3,7 +3,7 @@ #include "display.h" #include "font.h" #include "storage.h" -#include "modem.h" +#include "fecmodem.h" #include "system.h" animation_t ohai; diff --git a/src/modem.cc b/src/modem.cc index e9cddb7..472fe04 100644 --- a/src/modem.cc +++ b/src/modem.cc @@ -10,8 +10,9 @@ #include <avr/io.h> #include <stdlib.h> #include "modem.h" +#include "fecmodem.h" -Modem modem; +extern FECModem modem; /* * Returns number of available bytes in ringbuffer or 0 if empty @@ -24,7 +25,7 @@ uint8_t Modem::buffer_available() { * Store 1 byte in ringbuffer */ inline void Modem::buffer_put(const uint8_t c) { - if (modem.buffer_available() != MODEM_BUFFER_SIZE) { + if (buffer_available() != MODEM_BUFFER_SIZE) { buffer[buffer_head++ % MODEM_BUFFER_SIZE] = c; } } diff --git a/src/modem.h b/src/modem.h index ea308a7..4040c92 100644 --- a/src/modem.h +++ b/src/modem.h @@ -70,6 +70,4 @@ class Modem { void receive(void); }; -extern Modem modem; - #endif /* MODEM_H_ */ diff --git a/src/system.cc b/src/system.cc index a192b24..1a0522d 100644 --- a/src/system.cc +++ b/src/system.cc @@ -5,7 +5,7 @@ #include <stdlib.h> #include "display.h" -#include "modem.h" +#include "fecmodem.h" #include "storage.h" #include "system.h" |