add (untested) Hamming forward error correction code and corresponding class

The system now uses a FECModem instance, which inherits the receive methods
etc. from Modem.

Up next: Make the modem's buffer read methods private and expose them in
error-corrected FECModem methods instead

1 files changed, 37 insertions, 0 deletions

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_ */