Unable to perform IQ sampling normally

SW version :2.4.0
HW revision: nRF52833 development board, PCA20054 Direction Finding Antenna Board 1_0_0
I use the routine director_finding_central  and  director_finding_periopheral for IQ sampling, and can obtain IQ sampling data.
When I put the original
static const uint8_t ant_patterns[] = { 0x2, 0x0, 0x5, 0x6, 0x1, 0x4,
0xC, 0x9, 0xE, 0xD, 0x8, 0xA };
Change to
static const uint8_t ant_patterns[] = { 0xC, 0x9, 0xE, 0xD, 0x8, 0xA,
0x2, 0x0, 0x5, 0x6, 0x1, 0x4 };
The Bluetooth connection will disconnect, making it impossible to perform normal IQ sampling.
May I ask why this situation has occurred?


Below is the serial port output

  • Have you set this custom antenna pattern on both sides of the connection or just on the central side?

    I use AOA  mode and just set this custom antenna pattern on the central side

    How have you connected the antenna array to the nRF52833 DK on your end?

    Pin Header,  I will upload a picture later to show the connection

    So when you change the antenna pattern without changing the switch pattern they won't match

    the antenna pattern is passed as a parameter to this interface,so the switch pattern will change according to the antenna pattern

    Is there a specific reason you're playing around with the antenna switching patterns here?
    We want to use our own Antenna Board and antenna pattern,   so we need to verify different antenna switching patterns. 
    According to the code process,
    changing the value of static const uint8_t ant_catterns will also change the SWITCHPATTERN register, so I hope to confirm with you whether changing the antenna switching patterns can still obtain IQ sampling values normally
    To describe it accurately, I will explain it in Chinese
    我们打算使用我们自己设计的天线,天线切换的顺序也是我们自己定义的,所以我们想用 nRF52833 DK 和  PCA20054  Antenna Board 做验证,看看天线切换的顺序是否可以改变,但是现在我们改变天线切换顺序,板子的连接都不正常了。
    根据代码流程, 改变  static const uint8_t ant_patterns 的值,  SWITCHPATTERN 寄存器也会跟着改变,所以希望和你们确认,改变天线的切换顺序是否还能正常获取IQ采样值
  • These pictures show the connection between nRF52833 DK and Antenna Board

  • Hi

    Yes, it should be possible to get usable IQ samples from other antenna switching patterns as well, but the default one is the optimal one since it does one corner at a time. 

    I'm afraid the accurate Chinese description doesn't help much since I don't know Chinese, but I think what you need to do here is to make sure you match up the antenna switches to the pattern you're actually setting. You need to make sure the correct switch is used so that the application switches to the right antenna when doing sampling on the central side. I'm guessing the disconnections are caused by a timeout because the device switches to the incorrect antennas and thus not catching the expected data.

    Best regards,

    Simon

  • Can you confirm with your developers or testers whether different switching patterns will affect the connection of the device? If so, what could be the possible reasons for this.

    We use our own antenna board, and also find that different switching patterns  will affect the connection. An antenna  switching patterns can work normally at a certain position, but the connection may be disconnected at other positions.

    However, when we do not sample IQ data, that is, do not switch the antennas, any antenna can be connected normally. It seems that switching antennas will affect the connection.

    But we have not yet found an antenna  switching patterns that can be normally connected at all positions.

  • Hi

    Yep, I agree there must be something we're missing and have made an inquiry internally to find out what that might be. I'll get back to you when I hear back from the devs. Unfortunately some of the team is currently out of office, so it might take a while. I'll get back to you on Friday at the latest with an update in any case.

    Best regards,

    Simon

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