lib/rf_test/pn9.c

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/* Copyright (c) 2009 Nordic Semiconductor. All Rights Reserved.
 *
 * The information contained herein is confidential property of Nordic 
 * Semiconductor ASA.Terms and conditions of usage are described in detail 
 * in NORDIC SEMICONDUCTOR STANDARD SOFTWARE LICENSE AGREEMENT. 
 *
 * Licensees are granted free, non-transferable use of the information. NO
 * WARRENTY of ANY KIND is provided. This heading must NOT be removed from
 * the file.
 *              
 * $LastChangedRevision: 5717 $
 */

#include "pn9.h"

#define pn9_bit5 0x08
#define pn9_bit9 0x80

static uint8_t bits_9_to_2;
static bit bit_1;

void pn9_init(void)
{
    bits_9_to_2 = 0xFF;
    bit_1 = 1;
}

uint8_t pn9_get_byte(void)
{
    bit feedback;
    uint8_t i, out_value;

    out_value = bits_9_to_2;
    
    for (i = 0; i < 8; i++)
    {
        // Tap the register
        feedback =  
            ((((bits_9_to_2 & pn9_bit9)>>4) ^ (bits_9_to_2 & pn9_bit5)) == 0) ? 0 : 1;
        // Shift
        bits_9_to_2<<=1;
        bits_9_to_2 |= (uint8_t) bit_1;
        // Enter feedback
        bit_1 = feedback;
    } 

    return out_value;
}