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LAUNCHXL-CC26X2R1: IQ data acquisition issue

Cherry Zhou
Mastermind 22235 points
Part Number: LAUNCHXL-CC26X2R1


Hi team,

Here're some issues from the customer may need your help:

Three cc2642 transmit boards are used, one AOA-bostxl, and the AOAboostxl is loaded on the transmit board as passive.

1) The antenna data collected with 5.30sdk has two raw IQ data from passive and coordinator, why are the two data different? The IQ data of the codator is passed to it by passive, is that right?

2) Why does the sample_idx in each pkt in IQ data only collect 45 groups? (0-44) What determines it?

3) In collected IQ data, pkt can sometimes reach 178.Can they configure it by themselves?

４）There are two [0,1] antenna switches, and Figure 1 below shows IQ data acquired at different times at the same angle at the same location, but the total number of IQ data acquired is not the same. There are 4410, 4455 codator, why?

５）The total number of IQ data collected by passive is also inconsistent, with 3870, 3600, and 3460.

６）The above 1-5 questions are IQ data collected with sdk5.30. Doing the same experiment with skd5.20, sometimes the IQ data is only one copy of the coinetor IQ data, sometimes the passive and the codinatore are normal, what is the reason for that?

７）With sdk5.20, the total number of IQ data received from the codator is also different, with more than 400 groups and 700 groups.　The total number should be 512 groups?

８）If a 4-MHz, 2-us slot is used and the filtered IQ data is used, does the acquired IQ data contain data from the reference period (8us), antenna switching period (2us), and antenna settling period (1us)?

 Could you help check this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Guru** 101460 points

    Hi Cherry,

    Generally speaking, I would recommend to leverage the documentation here and in the SimpleLink Academy labs here.

    1) Each device (i.e. coordinator and passive) sample its own data. The IQ data changes base on the position of the devices, the exact time they sample the data,etc. In other words, it is impossible to have the exact same data on both devices.

    2) The number of IQ sample collected by packet depends on the CTE length and the sampling frequency.

    3) The number of packets sampled depends on the connection interval (or advertising interval for connection-less AoA) and the total sampling time. Knowing the connection interval you can determine the sampling time to collect IQ data on the number of packets wanted.

    4) The difference probably comes either from some packets being missed by the passive, either from one of the two devices stop sampling before the other. We see in the first column that the two devices did not reach the same packet number.

    5) Same as before. Depends on the number of packets missed.

    6) I guess in the first case the passive was either not properly configured, either not able to found the connection. The passive and the coordinator never store the IQ data collected in the same file.

    7) I guess questions 4 and 5 answer this.

    8) No, I don't think so.

    I hope this will help,

    Best regards,

  • 0 in reply to Clément
    TI__Mastermind 22235 points

    Hi,

    Thanks for your support.

    Clément said:
    2) The number of IQ sample collected by packet depends on the CTE length and the sampling frequency.

    The length of the CTE, 20, and the sampling frequency, 4 MHz, are based on the example and have not changed. And according to the documents, passive will store 512 sets of IQ data, but only (0-44) 45 sets of IQ data are available.

    Clément said:
    1) Each device (i.e. coordinator and passive) sample its own data. The IQ data changes base on the position of the devices, the exact time they sample the data,etc. In other words, it is impossible to have the exact same data on both devices.

    Master does not have an antenna module, only the inverted F antenna that comes with the cc2652.

    Meaning that master's IQ data is collected by master itself based on the location of the respond?

    Thanks and regards,

    Cherry

  • +1 in reply to Cherry Zhou
    TI__Guru** 101460 points

    Hi,

    - The screenshot shows the system is configured with 2us-slots, for sampling at 1MHz. As a consequence, the number of IQ samples obtained is correct (the 8 samples of the reference period + the 37 samples).

    - Having only one antenna does not actually prevent to sample IQ data. However, IQ data sampled using only one antenna  cannot be used to calculate an angle.

    Best regards,