4 Replies Latest reply on Mar 15, 2017 8:09 AM by ben.blaukopf

    Low RSSI using CYBLE-224110-00 (non-extended)


      I am experiencing low signal strength when using  the CYBLE-224110-EVAL in short range (i.e. PA/LNA disabled). My setup has it connected to the Pioneer CY8CKIT-042-BLE.


      I have a simple BLE component that's advertising at 0dB TX power. RSSI (as checked on multiple known-good Android handsets) when right next to it is around -77dB - it should be more like -40.


      If I enable the PA/LNA, then the RSSI improves massively to better than -30dB. However, the current will exceed our budget.


      Is there any reason  the signal strength is so poor with the PA/LNA disabled? 

        • 1. Re: Low RSSI using CYBLE-224110-00 (non-extended)

          Hi Ben,


          How exactly do you have the PA/LNA configured in your application? The "Enabling Extended Range Feature" section on page 16 of the current CYBLE-224110-00 datasheet describes how you should set up register values and output pins to operate the integrated PA/LNA. Most likely, you should enable everything but set the mode to 2 (pin P0[3] = 1 and pin P0[2] = 0) to enable TX/RX bypass mode, as described in the "Power Saving Measures with PA/LNA Operation" section following. If you simply turn off the PA/LNA completely, the RF path will probably be abruptly cut off such that the antenna cannot radiate properly when the chipset radio is attempting to transmit.

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          • 2. Re: Low RSSI using CYBLE-224110-00 (non-extended)

            That worked, thank you. Could you consider updating the documentation? I don't normally have to follow the instructions for enabling components that I *don't* want to use! Nonetheless, I had already read that section, but the description of bypass hardly matched my use-case.


            "Power Mode 2 (TX/RX Bypass) is not recommended for typical low power mode use. The Bypass mode should be considered if a transition from Extended Range functionality to short-range communication is desired on-the-fly. Transitions from Active mode to Bypass mode are only recommended after a BLE event has completed and no RF activity is in process. "


            To paraphrase, in order to not use the component, you have to enable it in the non-recommended mode. 

            2 of 2 people found this helpful
            • 3. Re: Low RSSI using CYBLE-224110-00 (non-extended)

              Hi Ben,


              I'm glad to hear that the problem is resolved. I'll follow up with the documentation team about clarifying this and other extended-range module datasheets for this use case.


              Out of curiosity, is there a reason that you chose the '224110 module (an extended-range device) for your design even though you are not intending to use the extended-range features? While there is certainly no harm in doing so, you may be able to reduce cost and possibly PCB footprint space if you select a module without the integrated PA/LNA component.

              • 4. Re: Low RSSI using CYBLE-224110-00 (non-extended)

                Thanks for chasing the docs team. We're using the module for its 105C temperature rating.