NRZI

gistfile1.txt

void nrzi_encode(uint8_t* buf, uint8_t* output, uint16_t len)
{
    uint8_t prev_nrzi_bit = 0;
    uint8_t nrz_bit;
    uint8_t nrzi_bit;
    uint8_t i, j;
    
    for (i=0; i<len; i++)
    {
        for (j=0; j<8; j++)
        {
            nrz_bit = buf[i]>>j & 0x01;
            
            if (nrz_bit == 0)
            {
                nrzi_bit = prev_nrzi_bit ^ 1;
            }
            else
            {
                nrzi_bit = prev_nrzi_bit;
            }
            
            output[i] = output[i] | ((nrzi_bit & 0x01) << j);
            printf("[%u] %1X -> %1X\n", j, nrz_bit, nrzi_bit);
            
            if (nrzi_bit)
                buf[i] |= (1 << j);
            else
                buf[i] &= ~(1 << j);
            
            prev_nrzi_bit = nrzi_bit;
        }
    }
}

void nrzi_decode(uint8_t* buf, uint8_t* output, uint16_t len)
{
    uint8_t prev_nrzi_bit = 0;
    uint8_t nrz_bit;
    uint8_t nrzi_bit;
    uint8_t i, j;
    
    for (i=0; i<len; i++)
    {
        for (j=0; j<8; j++)
        {
            nrzi_bit = buf[i]>>j & 0x01;
            
            if (nrzi_bit != prev_nrzi_bit)
            {
                nrz_bit = 0;
            }
            else
            {
                nrz_bit = 1;
            }
            
            output[i] = output[i] | ((nrz_bit & 0x01) << j);
            printf("[%u] %1X -> %1X\n", j, nrzi_bit, nrz_bit);
            
            prev_nrzi_bit = nrzi_bit;
        }
    }
}