3.4 PIC32CXBZ2 Three-Wire PTA Coexistence Design

PIC32CXBZ2 provides the Three-Wire Packet Traffic Arbitration (PTA) WLAN coexistence solution.

This coexistence solution provides three pins to exchange coordinating information between BT and WLAN. When a BT request (BT_ACTIVE=1) is received, the Wi-Fi device compares this external priority (BT_PRIORITY) request against the internal Wi-Fi priority to grant BT (WLAN_ACTIVE=0) or Wi-Fi (WLAN_ACTIVE=1)

The three pins are defined as:
  • BT_ACTIVE: This output pin is to tell that BT is using the RF resources. The signal is high when BT is asking and accessing the RF. The signal is low when BT is not using the RF.
  • BT_PRIORITY: This output pin is to tell the BT priority request. The signal is high when there is a high-priority BT request. The signal is low when there is a low priority request.
  • WLAN_ACTIVE: This input pin brings in the information about when the WLAN activities are taking place. The signal is high when WLAN is using the RF resources. The signal is low when WLAN is not using the RF.
    1. Coexistence Scenarios using PTA signal

      Scenario 1: Wi-Fi device grants BT device’s Request.

      The BT device wants to use BT RF. It raises a request and waits for WLAN grants to access RF.

      • T1: BT device raises the request by asserting BT_ACTIVE signal and BT_PRIORITY level before accessing BT RF active.
      • T2: Wi-Fi device grant the request by setting WLAN_ACTIVE to low. BT device access BT RF activities execution continuously.

      Scenario 2: Wi-Fi device rejects BT device’s request.

      The BT device wants to use BT RF. It raises a request and WLAN rejects the request.
      • T2: Wi-Fi device rejects the grant by asserting WLAN_ACTIVE signal. BT device stops the ongoing BT RF preparation.
      • T3: BT device de-asserts both BT_ACTIVE and BT_PRIORITY signals after stopping the BT RF preparation.

      Scenario 3: Wi-Fi device aborts the ongoing BT RF activity by raising WLAN_ACTIVE signal.

      The BT device is using BT RF. Wi-Fi raises a request and waits for BT to grant the RF access.

      • T9: BT device aborts the ongoing BT RF activity after detecting the WLAN_ACTIVE signal is asserted.
      • T8: BT device de-asserts both BT_ACTIVE and BT_PRIORITY signals after detecting the WLAN_ACTIVE signal is asserted.

      The following table summarizes the timing values:

      TimingMinimum (us)Maximum (us)
      T1––100
      T27580
      T3120160
      T8––100
      T9––45
    2. Hardware Information:

      The following dedicate GPIOs are assigned as PTA Pins, once the PTA feature is enabled..

      PTA Pin FunctionGPIO Pin
      BT_ACTIVEPA14
      BT_PRIORITYPA13
      WLAN_ACTIVEPB0
      48 pin package IC and WBZ451 provided MCC settings to enable PTA feature.
    3. Software Design Information
    Figure 3-289. MCC Configuration
    Users can enable this feature through the MCC settings provided in BLE stack.
    • PTA APIs in BLE_Stack library

      Two APIs are designed in BLE_Stack library.

      • BT_SYS_PtaInit – It is called within APP_PtaInit() to enable BLE stack PTA feature.
      • BT_SYS_PtaWlanActiveIrqHandler – It is called within APP_PtaWlanActiveIrqHandler() to handle WLAN_ACTIVE signal.
    • MCC Code Generation
      The following MCC configurations apply when BLE MCC component PTA option is enabled.
      • Includes PA14, PA13 and PB0 gpio setup in plib_gpio.c
      • Including app_pta_handler.c and app_pta_handler.h to project.
      • Generate application template code to call APP_PtaInit() in APP_BleStackInitAdvance().
      • The PTA feature will be enabled automatically through the above generated code
    • BT Request Priority Design

      Other Bluetooth activities are of high priority, with exceptions like Bluetooth scanning, packets advertising and RSSI measurements for channel classification.