nRF71 short-range coexistence driver

The nRF71 short-range (SR) coexistence driver coordinates the concurrent operation of the Wi-Fi® and short-range (Bluetooth® LE) radios on an nRF71 Series device, which integrates both radios on a single die.

Coexistence is arbitrated on-chip by the Coexistence Controller (COEXC) hardware together with a Coexistence Manager (CM) that runs in the Wi-Fi processor firmware. The Coexistence Driver (CD) is the host-side coordination layer between the Wi-Fi driver, the short-range driver, and the Coexistence Manager. This differs from the nRF70 Series, where a separate Wi-Fi companion arbitrates with an external short-range SoC over a wired Packet Traffic Arbitration (PTA) interface.

Overview

The coexistence driver performs the following functions:

• Exposes APIs (coex_cd_*) that the short-range and Wi-Fi drivers call to request short-range priority windows, report short-range activity, and notify radio power state changes.

• Invokes APIs (coex_sr_*) on the short-range driver to enable coexistence and to configure the short-range priorities.

• Forwards coexistence commands to, and processes events from, the Coexistence Manager over the Wi-Fi host-to-firmware control path.

The users of the driver are the nRF71 Wi-Fi driver and the short-range (Bluetooth LE) driver. Applications do not call it directly. The driver depends on the nRF71 Wi-Fi driver, because the command and event path to the Coexistence Manager runs over it, and it is only meaningful when the Wi-Fi radio is present.

Architecture

The following diagram shows the components and the interfaces between them:

The main interfaces are:

• Wi-Fi driver ↔ CD - Radio power state notifications (coex_cd_wifi_power_notify()), and the transport the CD uses to reach the Coexistence Manager (nrf71_wifi_coex_cmd_send() and nrf71_wifi_coex_on_event()).

• short-range driver ↔ CD - The short-range driver requests priority windows, reports activity, and notifies power state changes through coex_cd_*. The CD configures the short-range driver through coex_sr_*.

• CD ↔ Coexistence Manager - CD2CM commands and CM2CD events, carried over the Wi-Fi control path. The Coexistence Manager programs the COEXC hardware and handles hardware requests from the radios.

Relationship to MPSL coexistence

The Multiprotocol Service Layer (MPSL) coexistence feature (mpsl_cx) implements a wired-PTA request/grant interface for arbitrating a Nordic short-range radio against an external Wi-Fi companion. The nRF71 coexistence driver targets a different topology, supporting on-die arbitration between co-located radios through the COEXC hardware and the firmware Coexistence Manager. The two mechanisms are therefore independent, and the coexistence driver is a standalone driver rather than an MPSL coexistence backend.

Feature support

The following coexistence features are implemented in the current release:

• Startup coexistence configuration (Wi-Fi and short-range priority ranges and user parameters).

• Runtime Wi-Fi coexistence enable and disable.

• Radio power-down and power-up handling for the Wi-Fi and short-range drivers.

The following features are planned for a later phase, and are not available in the current release:

• Short-range Single Priority Window requests (a request returns -ENOTSUP).

• Periodic Priority Window generation, without and with alignment (a request returns -ENOTSUP).

• Thread activity Periodic Priority Windows.

• Scheduling service and runtime adaptive priority optimization.

• Wi-Fi channel or band change handling and the associated Bluetooth LE bad-channel mapping.

Configuration

To enable the driver, use the CONFIG_NRF71_SR_COEX_DRIVER Kconfig option. As coexistence involves both radios, the driver depends on the nRF71 Wi-Fi driver (CONFIG_WIFI_NRF71) and Bluetooth (CONFIG_BT).

The following Kconfig options configure the driver:

• CONFIG_NRF71_SR_COEX_DRIVER_INIT_PRIORITY - Sets the initialization priority within the APPLICATION initialization level, kept after the Wi-Fi driver.

• CONFIG_NRF71_SR_COEX_DRIVER_LOG_LEVEL - Sets the log level for the driver.

API documentation

The coexistence API contract (the coex_cd_* and coex_sr_* functions and the CD2CM/CM2CD message types) is defined by the coexistence firmware interface headers, which match the interface of the ROMed nRF71 firmware.

CD-to-CM interface header: drivers/wifi/nrf71/fw_if/nrf71_coex_if.h

CD-to-short-range interface header: drivers/wifi/nrf71/fw_if/nrf71_cd_sr_if.h

Wi-Fi transport header: include/drivers/wifi/nrf71/nrf71_wifi_coex.h

Source files: drivers/nrf71_sr_coex/src/

The following APIs are exposed by the coexistence driver to the short-range and Wi-Fi drivers:

• coex_cd_sr_software_client_request() - Requests or releases a short-range Single Priority Window (Phase 2; currently returns -ENOTSUP).

• coex_cd_update_short_range_activity_info() - Reports short-range activity for Periodic Priority Window generation (Phase 2; currently returns -ENOTSUP).

• coex_cd_sr_power_notify() - Notifies the coexistence driver of short-range power-down and power-up events.

• coex_cd_wifi_power_notify() - Notifies the coexistence driver of Wi-Fi power-down and power-up events.

The following APIs are exposed by the short-range driver and invoked by the coexistence driver:

• coex_sr_enable() - Enables or disables short-range coexistence.

• coex_sr_set_client_priority() - Configures the short-range client priority ranges.