GOLAY.c

#include

void golay_enc（u16* golay_enc_in u16* golay_enc_out）;

int golay_dec（u16* golay_dec_in u16* golay_dec_out）;

/**************************************************************************
 * Function: Golay（24128） Encoder and Decoder for DMR standard.         *
 * Reference:                                                             *
 *   1: DMR standard ts_10236101v010405p.pdf page 128.                   *
 *   2: Error Control Coding/Second Edition/Lin Shu/Ch04.pdf/page 27.     *
 *   3: Generator polynomial: g（X）=X^11+X^10+X^6+X^5+X^4+X^2+1=6165_oct   *
 *   4: There are two different generator polynomials.                    *
 *                                                                        *
 *************************************************************************/

//===== Bit Struct ====
//|<-    Info    ->|<-  Parity ->|
//________________________________
//|23|22| ...|13|12|11|10|...|1|0|
//----------------------------

//===== golay table ======
// G = [I_12 P]
// H = [Q I_12]
static const u16 P[] =
{
    0xc75  // 1100_0111_0101
    0x63b  // 0110_0011_1011
    0xf68  // 1111_0110_1000
    0x7b4  // 0111_1011_0100

    0x3da  // 0011_1101_1010
    0xd99  // 1101_1001_1001
    0x6cd  // 0110_1100_1101
    0x367  // 0011_0110_0111

    0xdc6  // 1101_1100_0110
    0xa97  // 1010_1001_0111
    0x93e  // 1001_0011_1110
    0x8eb   // 1000_1110_1011
};

static const u16 Q[] =     // Q = P‘ = inv（P）
{
    0xa4f  // 1010_0100_1111
    0xf68  // 1111_0110_1000
    0x7b4  // 0111_1011_0100
    0x3da  // 0011_1101_1010

    0x1ed  // 0001_1110_1101
    0xab9  // 1010_1011_1001
    0xf13  // 1111_0001_0011
    0xdc6  // 1101_1100_0110

    0x6e3  // 0110_1110_0011
    0x93e  // 1001_0011_1110
    0x49f  // 0100_1001_1111
    0xc75   // 1100_0111_0101
};

//===== golay_enc（） ======
// function: Golay（24128） encoder.
// input:   u16 golay_enc_in;
// output:  u16 golay_enc_out[2];
//          golay_enc_out[0] is info golay_enc_out[1] is parity.
// Both use low 12 bits. [golay_enc_out[0] golay_enc_out[1]] = golay_enc_in * G.
// No return value.
//#pragma CODE_SECTION （golay_enc “.text1“）
void golay_enc（u16* golay_enc_in u16* golay_enc_out）
{
    u16 i j;

    golay_enc_out[0] = *golay_enc_in;
    golay_enc_out[1] = 0;
    for（i = 0; i < 12; i++）
    {
        j = golay_enc_out[0] & Q[i];
        j = （j & 0xff） ^ （j >> 8）;
        j = （j & 0x0f） ^ （j >> 4）;
        j = （j & 0x03） ^ （j >> 2）;
        j = （j & 0x01） ^ （j >> 1）;
        golay_enc_out[1] = （golay_enc_out[1] << 1） ^ j;
    }
}

//===== golay_dec（） ======
// function: Golay（24128） decoder.
// input:   u16 golay_dec_in[2];
// output:  u16 golay_dec_out;
//          golay_dec_in[0]