nRF70 Series devices have a highly configurable coexistence hardware to help mitigate interference between WLAN and Bluetooth® LE/IEEE 802.15.4 devices (Thread®, Zigbee®).
A Packet Traffic Arbitration (PTA) module, connected to the CH logic function, facilitates the mitigation of various interference scenarios through a highly-programmable fabric. The coexistence hardware enables flexible output signals that support interface configurations like 3-wire and 4-wire. The primary schemes supported are:
- Shared Antenna mode – The PTA makes priority decisions, controls the switch between Bluetooth LE/IEEE 802.15.4 and Wi-Fi. The PTA also grants TX/RX requests from the Bluetooth LE/IEEE 802.15.4 device. Only one interface, either Bluetooth LE/IEEE 802.15.4 or or Wi-Fi is connected to the antenna at any time.
- Separate Antenna mode – The PTA makes priority decisions, granting TX/RX requests from Bluetooth LE/IEEE 802.15.4. Each interface is permanently connected to its own antenna.
The following figure shows the architecture of the coexistence hardware with details about the PTA control lines.
Figure 1. Coexistence hardware architecture
| Signal name | I/O | Requirement | Bluetooth LE/IEEE 802.15.4 signal (3-wire/4-wire) | Description | Scan-only function |
|---|---|---|---|---|---|
| COEX_REQ | Input | Mandatory for 3-wire and 4-wire | SR_REQUEST | Bluetooth LE/IEEE 802.15.4 device requesting a TX/RX transaction | Does not influence COEX_GRANT. |
| COEX_STATUS0 | Input | Mandatory for 3-wire and 4-wire | SR_STATUS | Indicates if the Bluetooth LE/IEEE 802.15.4 transaction is TX or RX. If the device supports a Priority signal, Priority is muxed with TX/RX on this signal based on the timing diagrams. | Does not influence COEX_GRANT. |
| COEX_GRANT | Output | Mandatory for 3-wire and 4-wire | SR_GRANT | Indicates that the Bluetooth LE/IEEE 802.15.4 device is granted access for this transaction. | Only de-asserted during a Wi-Fi scan operation in the 2.4 GHz band. |
| COEX_STATUS1/SW_CTRL1 | Input/Output | Optional for 3-wire | SR_PTI/RF_SW_CTRL1 | In 4-wire mode, this carries the Bluetooth LE/IEEE 802.15.4 1 bit priority signal. In 3-wire Shared Antenna mode, this can be optionally used as a second antenna switch control signal. | Does not influence COEX_GRANT in 4-wire mode. Can function as a second switch control signal in 3-wire mode. |
| SW_CTRL0 | Output | Mandatory for 3-wire and 4-wire Shared Antenna mode. Optional otherwise | RF_SW_CTRL0 | Used for antenna switch control in Shared Antenna mode. | Functions as a switch control in Shared Antenna mode. |
Note: The behavior of SW_CTRL0/1 is programmable and dependent on the
configured coexistence mode and switch control interface.