nRF9160dk Bluetooth HCI LPUART "Empty receiver state:4"

Question

Hello,

I am using an nRF9160dk with the nRF52840 acting as the BT controller running the Bluetooth: HCI low power UART sample (https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/bluetooth/hci_lpuart/README.html).

Development setup:

- nRF Connect SDK v2.3.0

- nRF9160DK, revision 1.1.0

The board scans correctly and I can connect successfully with an advertising device, however every time I reset the nRF9160DK (with the reset button) I get the following error:

[00:00:00.529,144] <wrn> lpuart: req pin low when expected high

[00:00:00.529,235] <err> lpuart: Empty receiver state:4

[00:00:01.226,196] <wrn> bt_hci_core: opcode 0x0000 pool id 3 pool 0x2000cc50 != &hci_cmd_pool 0x2000cca8

I use the following code on the nRF9160:

#include <stdio.h>
#include <zephyr/kernel.h>
#include <zephyr/console/console.h>
#include <zephyr/logging/log.h>

#include <zephyr/bluetooth/bluetooth.h>
#include <zephyr/bluetooth/uuid.h>
#include <bluetooth/scan.h>

LOG_MODULE_REGISTER(main);

/** @brief Random generated UUID. **/
#define BT_UUID_RAND_VAL \
    BT_UUID_128_ENCODE(0xf249bbe7, 0x4d87, 0x4322, 0xb9b2, 0x52b56dd0108e)

#define BT_UUID_RAND \
    BT_UUID_DECLARE_128(BT_UUID_RAND_VAL)

static int start_scan(void) {
    int err = bt_scan_start(BT_SCAN_TYPE_SCAN_PASSIVE);

    if (err) {
        LOG_ERR("Scanning failed to start (err %d)", err);
    }
	LOG_INF("Scanning successfully started");
    return err;
}

static void scan_filter_match(struct bt_scan_device_info *device_info, struct bt_scan_filter_match *filter_match, bool connectable)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(device_info->recv_info->addr, addr, sizeof(addr));

	LOG_INF("Device found: %s", addr);
}

static void scan_connecting_error(struct bt_scan_device_info *device_info)
{
	LOG_WRN("Connecting failed");
}

static void scan_connecting(struct bt_scan_device_info *device_info, struct bt_conn *conn)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(device_info->recv_info->addr, addr, sizeof(addr));

	LOG_INF("Connecting to device: %s", addr);
}

BT_SCAN_CB_INIT(scan_cb, scan_filter_match, NULL, scan_connecting_error, scan_connecting);

static void scan_init(void)
{
    int err;

	struct bt_le_scan_param scan_param = {
		.type = BT_LE_SCAN_TYPE_ACTIVE,
		.options = BT_LE_SCAN_OPT_FILTER_DUPLICATE,
		.interval = 0x0010,
		.window = 0x0010,
	};

    struct bt_scan_init_param scan_init = {
        .scan_param = &scan_param,
		.connect_if_match = true,
		.conn_param = BT_LE_CONN_PARAM_DEFAULT,
	};

    bt_scan_init(&scan_init);
    bt_scan_cb_register(&scan_cb);

	err = bt_scan_filter_add(BT_SCAN_FILTER_TYPE_UUID, BT_UUID_RAND);
	if (err)
	{
		LOG_ERR("Scanning filters cannot be set, err %d", err);
		return;
	}

	err = bt_scan_filter_enable(BT_SCAN_UUID_FILTER, false);
	if (err)
	{
		LOG_ERR("Filters cannot be turned on, err %d", err);
        return;
	}

    start_scan();
}

static void ble_ready(int err) {
    LOG_INF("Bluetooth ready");
    scan_init();
}

void main() {
	int err;

    LOG_INF("Initializing Bluetooth..");
    err = bt_enable(ble_ready);
    if (err) {
        LOG_ERR("Bluetooth init failed (err %d)", err);
        return;
    }
}

Here is the prj.conf:

# Logging
CONFIG_LOG=y
CONFIG_LOG_DEFAULT_LEVEL=3

# Enable Bluetooth stack and libraries
CONFIG_BT=y
CONFIG_BT_H4=y
CONFIG_BT_CENTRAL=y

CONFIG_BT_SCAN=y
CONFIG_BT_SCAN_FILTER_ENABLE=y
CONFIG_BT_SCAN_UUID_CNT=1

CONFIG_UART_INTERRUPT_DRIVEN=y

nrf9160dk_nrf9160_ns.conf:

CONFIG_NRF_SW_LPUART=y
CONFIG_NRF_SW_LPUART_INT_DRIVEN=y

CONFIG_UART_2_ASYNC=y
CONFIG_UART_2_INTERRUPT_DRIVEN=n
CONFIG_UART_2_NRF_HW_ASYNC=y
CONFIG_UART_2_NRF_HW_ASYNC_TIMER=2

Devicetree overlay for the nRF9160:

#include <nrf9160dk_nrf52840_reset_on_if5.dtsi>

/ {
	chosen {
		zephyr,bt-uart=&lpuart;
	};
};

&gpiote {
	interrupts = <49 NRF_DEFAULT_IRQ_PRIORITY>;
};

&uart2 {
	current-speed = <1000000>;
	status = "okay";
	/delete-property/ hw-flow-control;

	pinctrl-0 = <&uart2_default_alt>;
	pinctrl-1 = <&uart2_sleep_alt>;
	pinctrl-names = "default", "sleep";
	lpuart: nrf-sw-lpuart {
		compatible = "nordic,nrf-sw-lpuart";
		status = "okay";
		req-pin = <21>; /* <&interface_to_nrf52840 3 0>; */
		rdy-pin = <19>; /* <&interface_to_nrf52840 2 0>; */
	};
};

&pinctrl {
	uart2_default_alt: uart2_default_alt {
		group1 {
			psels = <NRF_PSEL(UART_TX, 0, 18)>,
				<NRF_PSEL(UART_RX, 0, 17)>;
		};
	};

	uart2_sleep_alt: uart2_sleep_alt {
		group1 {
			psels = <NRF_PSEL(UART_TX, 0, 18)>,
				<NRF_PSEL(UART_RX, 0, 17)>;
			low-power-enable;
		};
	};

};

Any help would be greatly appreciated.