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WL1837MOD: Bluetooth Boot Up Behavior

Brian Antheunisse
Expert 5335 points

Part Number: WL1837MOD
Other Parts Discussed in Thread: WL18XX-BT-SP

Hi team,

I have a customer using the WL1837MOD in their current system, but have it configured a little different than the hardware integration guide specifies. They will fix it next rev, but for now they need to understand the behavior in the following scenario:

We have tied BT_EN pin high on the module even though we are not using the Bluetooth functionality. According to the integration guide attached, it states on Page 15 as following:

 

”Once BT EN is asserted to high the BT FW stored in ROM start to execute, during this time the RTS is driven high to prevent HCI transaction and not to interfere with device boot, once the FW finish the boot process RTS line goes low after approximately 100 mS”

 

We are not using the BT functionality of the device and we are not loading any drivers from our OS for the BT. Unfortunately I don’t have access to the UART pins of the BT module in the WiLink chipset. So here are a few questions.

    • Coming out of reset, what is the BT mode if the driver/configuration is not loaded to the BT module?
    • Does the BT module go to sleep/hibernate coming out of reset if UART is not connected?
    • I looked at the attached User Guide for the WiLink module and section 5.1.1.6 shows that deep sleep in disabled by default. The question is if BT_EN pin is high and the WiLink comes out of reset and UART on the BT side is not connected, what is the expected behavior of the BT module. Since we load the Wi-Fi driver/config file to the WiLink, that seems to work just fine. We are going to hold BT_EN pin low in our next revision. 

Thanks,

Brian

  • 0
    TI__Expert 6335 points
    Brian,

    We have assigned your post to the relevant engineer and will get back to you.
  • 0
    TI__Mastermind 29361 points

    Brian,

    Brian Antheunisse said:

    We are not using the BT functionality of the device and we are not loading any drivers from our OS for the BT. Unfortunately I don’t have access to the UART pins of the BT module in the WiLink chipset. So here are a few questions.

      • Coming out of reset, what is the BT mode if the driver/configuration is not loaded to the BT module?


    If BT is not being used, it must not be enabled in the first place. Since the BT_EN is tied to logic-high in this case, it will not follow the proper BT power-up sequence as explained in the datasheet. So in this case, the BT will be in an unknown/unstable state if you just have the BT_EN tied to high.

    Brian Antheunisse said:
      • Does the BT module go to sleep/hibernate coming out of reset if UART is not connected?


    No. The initscript/service-pack (WL18xx-BT-SP) must be loaded before the BT IP goes into sleep or low power state. But as mentioned above, the BT_EN is not following the proper power-up sequence. So loading the initscript/service-pack will fail as well.

    Brian Antheunisse said:
      • I looked at the attached User Guide for the WiLink module and section 5.1.1.6 shows that deep sleep in disabled by default. The question is if BT_EN pin is high and the WiLink comes out of reset and UART on the BT side is not connected, what is the expected behavior of the BT module. Since we load the Wi-Fi driver/config file to the WiLink, that seems to work just fine. We are going to hold BT_EN pin low in our next revision. 

    The deep sleep mentioned in the SWRU442 section 5.1.1.6 is only for the BT IP of the WiLink device. It is independent from any WLAN activity (or lack of activity).

    Best regards,

    Vihang