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Original question:

CC3235MODS: ANT_SEL1 and ANT_SEL2 pins of CC3235MODx

CC3235MODS: How to use with diversity antenna

O.H
Genius 5795 points
Part Number: CC3235MODS

Hi experts,

My customer is planning to implement two types of antennas at the same time: a chip antenna and an external antenna. They expect to receive signals from both antennas during application execution and use the antenna with better signal conditions. (Diversity operation). For example, if there are two antennas, A and B, and A is not receiving, B will receive.

I believe the above can be achieved by using the "Antenna Selection (CC3235MODx only)" function of the CC3235MODx, but I would like to confirm the following points.

Q1: Is it possible to switch between "ANT1" and "ANT2" of "Antenna Selection (CC3235MODx only)" while the application is running?
If it is possible to switch between ANT_SEL1 and ANT_SEL2 based on the radio wave status depending on the processing of the application, we think it is possible to achieve what the customer wants to do.

Q2: Is it possible to use the "Autoselect" option of "Antenna Selection (CC3235MODx only)" to automatically switch antennas multiple times while the application is running?
The "Autoselect" option in Antenna Selection (CC3235MODx only) automatically switches to the antenna with the best signal condition. However, after that, the first selected antenna will be used, so I understood that automatic switching is not possible. (Because it needs to be reset to switch automatically again.)

It is a requirement for customers to use two antennas simultaneously. If you have any helpful application notes or another solution, it would be appreciated.

Best regards,
O.H

  • +1
    TI__Mastermind 40965 points

    Hi,

    Yes, the antenna diversity feature is designed to address the need to use two antennas, and pick the appropriate antenna with better signal quality during runtime.

    To answer your questions:

    1. Yes, it is possible to switch the antennas while your application is running. However, you cannot manually switch while connected to an AP. Also, if you are using auto mode, you cannot switch once connected. You will need to trigger a manual disconnect to allow the auto algorithm to run again.

    2. Again, you can switch in your application as much as you need, but only during the connection phase - once connected you are fixed to one antenna.

    More info on the antenna diversity feature can be found in section 4.8 of the NWP user's guide: www.ti.com/lit/swru455

    The simplest method that would work would be to keep monitoring the RSSI in the application, then trigger a disconnect when the RSSI has been detected as below your application's minimum threshold.

    Also, depending on your customer's use case, the auto behavior of the CC3235 is likely sufficient, especially if it is in a product that is designed to be stationary during operation. If the device is not in a changing RF environment, the antenna that is found to have better signal strength during connection is unlikely to change.

    Regards

    Michael

  • 0 in reply to Michael Reymond
    Genius 5795 points

    Hi Michael,

    Thanks for the reply. Sorry, I missed " I missed the "section 4.8 of the NWP user's guide". I checked the documentation, but one question arose, so let me check.

    Q3: In "section 4.8.2 Configuration" of the NWP user's guide, it says that I have to reset the device to switch the Mode. This is just a Mode switch.
    ~~~~~~~~~~~~~~~~~~~~~~~~~
    4.8.2 Configuration
    The configuration of this feature is possible through the Host APIs. The possible configuration includes the mode of the feature and the antennas’ pad number ("pin mux"). This configuration is persistent. Reset is required to apply the changes.
    ~~~~~~~~~~~~~~~~~~~~~~~~~

    Is it correct that this is only for Mode switching, so resetting is not necessary for ANT_SEL1 and 2 switching?
    Or, once connected to the AP, do I need to manually disconnect and reset the device in order to switch between ANT_SEL1 and 2?

    Best regards,
    O.H

  • 0 in reply to O.H
    TI__Mastermind 40965 points

    Hi O.H,

    Resetting is not needed for antenna switching, only if you want to change modes from AUTO to ANT1 or ANT2 only. So if you're in AUTO mode, you don't need to perform a reset if you want to switch antennas.

    You do however need to disconnect from the AP in order to switch antennas. So if you have detected that the RSSI measured by the inactive antenna has become better than the currently-used one, then you will need to perform a manual disconnect in order to get the current NWP to perform an AUTO mode scan and switch, during the next connection phase.

    Regards,

    Michael

  • 0 in reply to Michael Reymond
    Genius 5795 points

    Hi Michael,

    Thank you for your reply.

    Michael Reymond said:
    Resetting is not needed for antenna switching, only if you want to change modes from AUTO to ANT1 or ANT2 only. So if you're in AUTO mode, you don't need to perform a reset if you want to switch antennas.

    Could you please tell me what "a reset is required" means in the following content of the datasheet? For example, hard reset of the device, soft reset, reset of the AP connection sequence, etc. The following is from the datasheet "10.1.2 Antenna Selection (CC3235MODx only)".
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Autoselect: When selected, during a scan and prior to connecting to an AP, CC3235MODx device will determine the best RF path and select the appropriate antenna(13)(14). The result is the saved as port of the profile.

    (13): When selecting Autoselect via the API, a reset is required in order for the CC3235MODx device to determine the best antenna for use.
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    The above answer says that no reset is required to switch antennas, whether in Auto Mode or not, but the datasheet says that a reset is required to select the antenna when Auto Mode is selected.

    There is a difference in the content and I am confused, so I would appreciate it if you could tell me.

    Best regards,
    O.H

  • 0 in reply to O.H
    TI__Mastermind 40965 points

    Hi O.H,

    In the datasheet, the reset that it is referring to is an NWP reset (through sl_Stop/sl_Start), that is needed when the operation mode is switched to Autoselect. Once autoselect (AUTO mode) is enabled then there is no reset required for the NWP to automatically switch antennas during connection.

    Regards,

    Michael

  • 0 in reply to Michael Reymond
    Genius 5795 points

    Hi Michael,

    Sorry for the late reply. I understood. Thank you for your kind support!!

    Best regards,
    O.H