xref: /btstack/chipset/cinnamon/hopping.c (revision 2c4f9bbb6d93b3f1a90ed62ac67e4cd019f0736a)

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#include <string.h>
#include <strings.h>
#include <assert.h>

#include "debug.h"
#include "hopping.h"

#define GET_BIT( b, n )  ((b[(n&UINT32_C(0xFFFFFFF8))>>3]>>(n&0x7))&1)

void hopping_init( hopping_t *c ) {
    assert( c != NULL );

    memset( c, 0, sizeof(hopping_t) );
}

void hopping_set_channel_map( hopping_t *c, const uint8_t *chm ) {
    assert( c != NULL );
    assert( chm != NULL );

    memcpy( c->chMap, chm, 5 );

    c->chCnt = 0;
    for(int i=0; i<37; ++i) {
        LOG_DBG("%d(%d)\n", i, (i&UINT32_C(0xFFFFFFF8))>>3 );
        LOG_DBG("%d(%d)\n", i, GET_BIT( c->chMap, i ) );
        if( 1 == GET_BIT( c->chMap, i ) ) {
            c->chRemap[c->chCnt++] = i;
        }
    }

//    for(int i=0; i<c->chCnt; ++i)
//        printf("%d\n", c->chRemap[i] );

//    printf("chCnt: %d\n", c->chCnt );
}

void hopping_csa1_set_hop_increment( hopping_t *c, uint8_t hopIncrement ){
    assert( c != NULL );

    c->hopIncrement = hopIncrement;
}

uint8_t hopping_csa1_get_next_channel( hopping_t *c ) {
    assert( c != NULL );

    c->currentCh = (c->currentCh + c->hopIncrement) % 37;
    if( 1 == GET_BIT( c->chMap, c->currentCh ) ) {
        return c->currentCh;
    } else {
        return c->chRemap[ c->currentCh % c->chCnt ];
    }
}

// channelIdentifier = (Access Address31-16) XOR (Access Address15-0)
void hopping_csa2_set_access_address( hopping_t *c, uint32_t accessAddress ){
    assert( c != NULL );

    c->channelIdentifier = (accessAddress >> 16) ^ (accessAddress & 0xffff);
}

// @TODO rbit intrinsic could be used
static uint16_t hopping_csa2_permutation(uint16_t v){
    v = ((v >> 1) & 0x5555) | ((v & 0x5555) << 1);
    v = ((v >> 2) & 0x3333) | ((v & 0x3333) << 2);
    v = ((v >> 4) & 0x0F0F) | ((v & 0x0F0F) << 4);
    return v;
}

static uint16_t hopping_csa2_mam(uint16_t a, uint16_t b){
    return (17 * a) + b;
}

static uint16_t hopping_csa2_prn_e(hopping_t *c, uint16_t counter){
    assert( c != NULL );

    // see Bluetooth Spec v5, 4.5.8.3.3 Unmapped Event Channel Selection
    uint16_t v = counter ^ c->channelIdentifier;
    v = hopping_csa2_permutation (v);
    v = hopping_csa2_mam(v, c->channelIdentifier);
    v = hopping_csa2_permutation (v);
    v = hopping_csa2_mam(v, c->channelIdentifier);
    v = hopping_csa2_permutation (v);
    v = hopping_csa2_mam(v, c->channelIdentifier);
    v = v ^ c->channelIdentifier;
    return v;
}

uint8_t hopping_csa2_get_channel_for_counter( hopping_t *c, uint16_t counter ){
    assert( c != NULL );

    uint16_t prn_e = hopping_csa2_prn_e( c, counter);
    uint16_t unmapped_channel = prn_e % 37;
    if ( 1 == GET_BIT( c->chMap, unmapped_channel)){
        return unmapped_channel;
    } else {
        uint16_t remappingIndex = (((uint32_t) c->chCnt) * prn_e) >> 16;
        return c->chRemap[ remappingIndex ];
    }
}