nRF52840 BLE 3-Wire PTA for Wi-Fi

[Jayant Tang]

Hello DevZone,

I'm developing nRF52840 BLE & ESP32 Wi-Fi coexistence with 3-Wire PTA. I followed this document: https://docs.nordicsemi.com/bundle/ncs-2.5.3/page/nrf/device_guides/wifi_coex.html#generic_three_wire_coexistence

However, the NCS only support generic 3-wire PTA for OpenThread. So, I decided to write my own PTA code.

I modified `peripheral_uart` example. Added my code (with MPSL CX API).

The MPSL code is not difficult to understand. I referred to nrf/subsys/mpsl/cx/thread/mpsl_cx_thread.c

and nrf/subsys/mpsl/cx/nrf700x/mpsl_cx_nrf700x.c.

You can check my code as attached.

1488.peripheral_uart.7z

If you want to run this code, use NCS 2.5.3. And add the following Kconfig chioce to MPSL_CX_CHOICE in nrf/subsys/mpsl/cx/Kconfig 

config MPSL_CX_BT_3WIRE
    depends on SOC_SERIES_NRF52X
    select NRFX_GPIOTE
	select GPIO
	select NRFX_TIMER1
	bool "Bluetooth Radio 3-Wire Coexistence"

The problem is that the BLE activity is not controlled by the GRANT pin

No matter how I change the GRANT pin, the BLE connection is always good. And it never controls the REQUEST pin and PRIORITY pin.

Best regards,

Jayant

[Amanda Hsieh]

Hi,

The generic three-wire coex implementation (CONFIG_MPSL_CX_THREAD), despite the confusing name, also supports BLE as it implements the MPSL generic coex API (https://docs.nordicsemi.com/bundle/ncs-2.5.3/page/nrf/device_guides/wifi_coex.html#ug-radio-coex-mpsl-cx-based)

Try to enable CONFIG_MPSL_CX_THREAD=y in prj.conf instead to see if this protocol works for your requirements.

Regards,
Amanda H.

[Jayant Tang]

Hi Amanda,

This config CONFIG_MPSL_CX_THREAD=y does not work.

By default, it can't be enabled in BLE samples, because the nrf/subsys/mpsl/cx/Kconfig says this Kconfig `depends on !BT`. So, I deleted the line `depends on !BT`. 

The REQUEST pin and PRIORITY pin still not change state. And I can't connect to the DK with my nRF Connect App. The BLE advertising stopped just after startup.

 Best regards,

Jayant

[Jayant Tang]

I have some updates.

1. I find out that the MPSL does not call the `register_callback` function. So, my code didn't get the callback function.  

2. I tried a different way to enable 3-wire PTA in MPSL. I referred to nrf/subsys/mpsl/cx/bluetooth/mpsl_cx_1w_bluetooth.c

It doesn't work, too.

You can replace the same name file in my project (previously provided) with this file.

Fullscreen mpsl_cx_3w_bluetooth.c Download

/*
 * Copyright (c) 2022 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 */

/**
 * @file
 *   This file implements a generic bluetooth external radio 3w coexistence
 *   interface.
 *
 */

#include <stddef.h>
#include <stdint.h>

#include <zephyr/kernel.h>
#include <zephyr/device.h>
#include <zephyr/drivers/gpio.h>
#include <zephyr/devicetree.h>
#include <nrfx.h>
#include <nrfx_ppi.h>
#include <nrfx_gpiote.h>

#include <mpsl_coex.h>

#if DT_NODE_HAS_STATUS(DT_PHANDLE(DT_NODELABEL(radio), coex), okay)
#define COEX_NODE DT_PHANDLE(DT_NODELABEL(radio), coex)
#else
#define COEX_NODE DT_INVALID_NODE
#error No enabled coex nodes registered in DTS.
#endif

#if !(DT_NODE_HAS_COMPAT(COEX_NODE, generic_radio_coex_three_wire))
#error Selected coex node is not compatible with generic-radio-coex-three-wire.
#endif

#if !IS_ENABLED(CONFIG_SOC_SERIES_NRF52X)
#error Bluetooth 3-wire coex is only supported on the nRF52 series
#endif

#define MPSL_COEX_BT_GPIO_POLARITY_GET(dt_property)                                                \
	((GPIO_ACTIVE_LOW & DT_GPIO_FLAGS(COEX_NODE, dt_property)) ? false : true)

static volatile bool coex_enabled;

static void coex_enable_callback(void)
{
	coex_enabled = true;
}

static const struct gpio_dt_spec req_spec = GPIO_DT_SPEC_GET(COEX_NODE, req_gpios);
static const struct gpio_dt_spec pri_spec = GPIO_DT_SPEC_GET(COEX_NODE, pri_dir_gpios);
static const struct gpio_dt_spec gra_spec = GPIO_DT_SPEC_GET(COEX_NODE, grant_gpios);

static int mpsl_cx_bt_interface_3wire_config_set(void)
{
	nrfx_err_t err = NRFX_SUCCESS;
	nrf_ppi_channel_t ppi_channel;
	mpsl_coex_if_t coex_if_bt;
	mpsl_coex_802152_3wire_gpiote_if_t *coex_if = &coex_if_bt.interfaces.coex_3wire_gpiote;
    int32_t ret;
    
    ret = gpio_pin_configure_dt(&req_spec, GPIO_OUTPUT_INACTIVE);
	if (ret != 0) {
		return ret;
	}

	ret = gpio_pin_configure_dt(&pri_spec, GPIO_OUTPUT_INACTIVE);
	if (ret != 0) {
		return ret;
	}

	ret = gpio_pin_configure_dt(&gra_spec, GPIO_INPUT | GPIO_PULL_UP);
	if (ret != 0) {
		return ret;
	}

	/* Allocate GPIOTE and PPI channels for the 3 lines */
    mpsl_coex_gpiote_cfg_t *gpiote_cfg[3] = {
        &(coex_if->grant_cfg),
        &(coex_if->priority_cfg),
        &(coex_if->request_cfg)
    };
    uint8_t gpio_pin[3] = {
        NRF_DT_GPIOS_TO_PSEL(COEX_NODE, grant_gpios),
        NRF_DT_GPIOS_TO_PSEL(COEX_NODE, pri_dir_gpios),
        NRF_DT_GPIOS_TO_PSEL(COEX_NODE, req_gpios),
    };
    uint8_t gpio_polar[3] = {
        MPSL_COEX_BT_GPIO_POLARITY_GET(grant_gpios),
        MPSL_COEX_BT_GPIO_POLARITY_GET(pri_dir_gpios),
        MPSL_COEX_BT_GPIO_POLARITY_GET(req_gpios),
    };

    for(int i = 0; i < 3; i++){
        if (nrfx_gpiote_channel_alloc(&(gpiote_cfg[i]->gpiote_ch_id)) != NRFX_SUCCESS) {
            return -ENOMEM;
        }
        if (nrfx_ppi_channel_alloc(&ppi_channel) != NRFX_SUCCESS) {
            return -ENOMEM;
        }
        gpiote_cfg[i]->gpio_pin = gpio_pin[i];
        gpiote_cfg[i]->active_high = gpio_polar[i];
        gpiote_cfg[i]->ppi_ch_id = ppi_channel;
    }

    /* Allocate additional PPI channel for setting the priority level at the correct time */
    /* Since Priority and Status are combined functional, it requires separate PPI channel to handle both */
    if (nrfx_ppi_channel_alloc(&ppi_channel) != NRFX_SUCCESS) {
        return -ENOMEM;
    }
    coex_if->additional_ppi_ch_id = ppi_channel;

    /* When the PRIORITY pin indicates the Status.*/
    /* TX is the active level */
    coex_if->is_rx_active_level = 0;

    /* Delay in us from the request pin is raised until the Priority and Status line shows the type of transaction (RX/TX). */
    coex_if->type_delay_us = 0;

    /* Delay in us from the Priority and Status line shows the type of transaction, to the radio starts its on-air activity. */
    coex_if->radio_delay_us = 50;

    /* Pointer to a timer instance. Timer should not be shared with any other functionality. */
    coex_if->p_timer_instance = NRF_TIMER2;


	/* Enable support for coex APIs (make sure it's not link-time optimized out) */
	mpsl_coex_support_802152_3wire_gpiote_if();

	/* Enable 1-wire coex implementation */
	coex_if_bt.if_id = MPSL_COEX_802152_3WIRE_GPIOTE_ID;
	err = (int)mpsl_coex_enable(&coex_if_bt, coex_enable_callback);
    __ASSERT(err, "Failed to configure finished");

	/** If enable API call is successful, wait for initialization to complete
	 *  by waiting for the supplied callback to be called.
	 */
	while (!err && !coex_enabled) {
		k_yield();
	}
    printk("3-wire coex enabled\n");
	return err;
}

static int mpsl_cx_init(void)
{

	return mpsl_cx_bt_interface_3wire_config_set();
}

SYS_INIT(mpsl_cx_init, APPLICATION, CONFIG_KERNEL_INIT_PRIORITY_DEVICE);

[Amanda Hsieh]

Hi, 

For now, you can use the following workaround:

• Add CONFIG_BT_LL_SOFTDEVICE_MULTIROLE=y to prj.conf - this is required as coex is not included in the peripheral library, and currently this is not correctly getting selected automatically when coex is enabled.
• Remove the line depends on !BT as the customer has already done, and use CONFIG_MPSL_CX_THREAD=y

The developer has tested this locally and it works on our side, note enabling the multirole library is required for coex to work. This will not build as-is on NCS latest due to a regression, but is fine on 2.5.3. Will be fixed soon and will be part of NCS 2.8.

-Amanda H.

[Jayant Tang]

Hello Amanda,

That works for me. Thank you very much.

But I have a further question:

In `nrf/subsys/mpsl/cx/thread/mpsl_cx_thread.c:130`.

We can see in the `request()` function that it will activate the PRIORITY pin only if the priority>127.

The priority is a numerical value. Do we have any document about the value meaning?

/**
 * @brief Priority of given radio operation.
 *
 * This numerical value is translated by given PTA interface driver to appropriate signal.
 * The straightforward translation would be <= UINT8_MAX/2 is low priority, while > UINT8_MAX/2
 * is high priority. More complicated PTAs support more than 2 priority levels and valid matching
 * must be implemented for such devices.
 *
 * Priority values must be aligned between all users of this API in given system. When multiple
 * radio protocols are enabled (like Bluetooth LE and IEEE 802.15.4), all protocols must use
 * aligned values (Bluetooth low priority operations must use numerically lower value than
 * IEEE 802.15.4 high priority operations).
 */
typedef uint8_t mpsl_cx_prio_t;

Best regards,

Jayant

[Amanda Hsieh]

I only found this https://docs.nordicsemi.com/bundle/ncs-2.7.0/page/nrfxlib/mpsl/doc/api.html#c.mpsl_cx_prio_t which has the same content as you provided.