Updated lower limit of 'inter' when recovering hop interval.

[fO-000]

We expect a complete hop sequence cycle when recovering the hop interval. So the inter should be greater than (HOPSEQ_PERIOD - 1) * MIN_HOPINTER) = 216, which HOPSEQ_PERIOD is 37 and MIN_HOPINTER is 7.5 ms / 1.25 ms = 6.

In any case I would like to hear your opinions. 😊

[virtualabs]

I think you are right.

Originally, this check was introduced to avoid errors as our sniffer may receive both packets (TX/IDLE packet) from central and (RX/ACK packet) from peripheral devices. It may be a good idea to update this value to its theoretical minimum (i.e. 216), but since we are performing this test on a unique channel (not reused in the hopping sequence), we would obviously avoid to catch two packets belonging to a single connection event. In my opinion, this fix will also work but will also remove the fact that we are trying to avoid false-positive measures.

I don't see the need to apply this fix, unless it improves the performance of Bltejack. It is more of a cosmetic fix to me (yet correct and motivated fix too, i cannot deny), and I will consider fixing this in the next release of this firmware. Yes, I'm still working on it, but since it implies modifying large parts of this version, I would prefer delay this fix and test it along some other modifications I'm currently working on.

[fO-000]

Did you mean we only receive packets which PDU is empty, like TX/IDEL packets and RX/ACK packets, when recovering hop interval (and channel map, hop increment)?

And this is implemented by configuring NRF_RADIO->PCNF1 in radio_follow_aa() function?

[fO-000]

If so, why we configure MAXLEN field of NRF_RADIO->PCNF1 as 37UL in radio_follow_aa()?

    /* Packet configuration */
    NRF_RADIO->PCNF1 = (
      (((37UL) << RADIO_PCNF1_MAXLEN_Pos) & RADIO_PCNF1_MAXLEN_Msk)   |                      /* Maximum length of payload in bytes [0-255] */
      (((0UL) << RADIO_PCNF1_STATLEN_Pos) & RADIO_PCNF1_STATLEN_Msk)   |                      /* Expand the payload with N bytes in addition to LENGTH [0-255] */
      (((3UL) << RADIO_PCNF1_BALEN_Pos) & RADIO_PCNF1_BALEN_Msk)       |                      /* Base address length in number of bytes. */
      (((RADIO_PCNF1_ENDIAN_Little) << RADIO_PCNF1_ENDIAN_Pos) & RADIO_PCNF1_ENDIAN_Msk) |  /* Endianess of the S0, LENGTH, S1 and PAYLOAD fields. */
      (((1UL) << RADIO_PCNF1_WHITEEN_Pos) & RADIO_PCNF1_WHITEEN_Msk)                         /* Enable packet whitening */
    );