BLE How to set the device name dynamically

[lcj]

I have seen a few posts including:

•  Change advertised name (Bluetooth) - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com)
• NCS bt_set_name() - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com)
• Setting Bluetooth Device Name in Zephyr - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com)

but I still haven't been able to adapt one of the examples to show the name dynamically.

 

This is the code:

#include <zephyr/kernel.h>
#include <zephyr/logging/log.h>
#include <zephyr/bluetooth/bluetooth.h>
#include <zephyr/bluetooth/gap.h>
#include <zephyr/bluetooth/uuid.h>
#include <zephyr/bluetooth/conn.h>
#include <dk_buttons_and_leds.h>

#include <stdio.h> // For snprintf
#include <stdlib.h>

#include "ble_manager.h"


LOG_MODULE_REGISTER(ble_manager, LOG_LEVEL_DBG);

#define DEVICE_NAME             CONFIG_BT_DEVICE_NAME
#define DEVICE_NAME_LEN         (sizeof(DEVICE_NAME) - 1)


/* STEP 2.1 - Declare the Company identifier (Company ID) */
#define COMPANY_ID_CODE 0x0059

/* STEP 2.2 - Declare the structure for your custom data  */
typedef struct adv_mfg_data {
	uint16_t company_code; /* Company Identifier Code. */
} adv_mfg_data_type;


/* STEP 5.1 - Create the advertising parameter for connectable advertising */
static struct bt_le_adv_param *adv_param = BT_LE_ADV_PARAM(
	(BT_LE_ADV_OPT_CONNECTABLE | BT_LE_ADV_OPT_USE_IDENTITY), /* Connectable advertising and use identity address */
	800, /* Min Advertising Interval 500ms (800*0.625ms) */
	801, /* Max Advertising Interval 500.625ms (801*0.625ms) */
	NULL); /* Set to NULL for undirected advertising */

/* STEP 2.3 - Define and initialize a variable of type adv_mfg_data_type */
static adv_mfg_data_type adv_mfg_data = { COMPANY_ID_CODE, 0x00 };



static const struct bt_data ad[] = {
	BT_DATA_BYTES(BT_DATA_FLAGS, BT_LE_AD_NO_BREDR),
	//BT_DATA(BT_DATA_NAME_COMPLETE, DEVICE_NAME, DEVICE_NAME_LEN),
    /* STEP 3 - Include the Manufacturer Specific Data in the advertising packet. */
	BT_DATA(BT_DATA_MANUFACTURER_DATA, (unsigned char *)&adv_mfg_data, sizeof(adv_mfg_data)),
};

static unsigned char url_data[] ={0x17,'/','/','a','c','a','d','e','m','y','.',
                                 'n','o','r','d','i','c','s','e','m','i','.',
                                 'c','o','m'};

static const struct bt_data sd[] = {
        BT_DATA(BT_DATA_URI, url_data,sizeof(url_data)),
};

static void connected(struct bt_conn *conn, uint8_t err)
{
	if (err) {
		LOG_ERR("Connection failed (err %u)\n", err);
		return;
	}

	LOG_DBG("Connected\n");
}

static void disconnected(struct bt_conn *conn, uint8_t reason)
{
	LOG_DBG("Disconnected (reason %u)\n", reason);
}

BT_CONN_CB_DEFINE(conn_callbacks) = {
	.connected        = connected,
	.disconnected     = disconnected,
};


int ble_manager_init()
{
    LOG_DBG("Starting '%s'", DEVICE_NAME);

    int err;

    err = bt_enable(NULL);
    if (err) {
        LOG_ERR("Bluetooth init failed (err %d)", err);
        return -1;
    }
    LOG_DBG("Bluetooth initialized");

    // Generate a random 6-digit number
    unsigned int random_number = 100000 + rand() % 900000; // Ensures a range from 100000 to 999999
    LOG_DBG("Random number: %d", random_number);

    // Assuming random_number is already defined and holds a random 6-digit number
    char device_name[18]; // Ensure this is large enough to hold the resulting string
    
    // Create a formatted string with the random number
    snprintf(device_name, sizeof(device_name), "DeviceName %d", random_number);
    
    // Set the Bluetooth device name
    bt_set_name(device_name);
    LOG_DBG("Bluetooth device name: %s", device_name);

    err = bt_le_adv_start(adv_param, ad, ARRAY_SIZE(ad),sd, ARRAY_SIZE(sd));
    if (err) {
        LOG_ERR("Advertising failed to start (err %d)", err);	
        return -1;
    }

    LOG_DBG("Bluetooth advertising");

    return 0;
}

And this is the prj.conf:

# Logger module
CONFIG_LOG=y

# Button and LED library
CONFIG_DK_LIBRARY=y

# Bluetooth LE
CONFIG_BT=y
CONFIG_BT_PERIPHERAL=y
#CONFIG_BT_DEVICE_NAME="TEST Peripheral"
CONFIG_BT_DEVICE_NAME_DYNAMIC=y
# Maximum chcaracter of the device name
# (Range: 2 to 248)
CONFIG_BT_DEVICE_NAME_MAX=17

# Increase stack size for the main thread and System Workqueue
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048
CONFIG_MAIN_STACK_SIZE=2048

Is there something else I need to do either in the bt_data or in the bt_le_adv_start?

[Simonr]

Hi

In the second link you provided, Einar explains that most scanners/phones will cache the device name, so in most cases you need to toggle Bluetooth on/off on the scanner side to update a name on the scanner. If you've already done that, you should make sure that the name is updated in the advertising packet with bt_le_adv_update_data() which I don't see you're using.

Best regards,

Simon

[lcj]

I did turn Bluetooth on and off.

I tried adding:

// Set the Bluetooth device name
bt_set_name(device_name);
LOG_DBG("Bluetooth device name: %s", device_name);

err = bt_le_adv_update_data(ad, ARRAY_SIZE(ad), sd, ARRAY_SIZE(sd));
if (err) {
    LOG_ERR("Failed to update (err %d)", err);
    return -1;
}

and got:

[00:00:00.470,611] <err> ble_manager: Failed to update (err -11)

but I don't know why I would need to update the data if I'm setting the name before I start advertising. I guess that's my question. What is the right order of methods to call in order to set the name dynamically.

[Simonr]

Hi

First off, what SDK version are you using here. I just want to make sure we start on the same page here. It might seem like either the Bluetooth stack isn't initialized yet or that the advertiser is busy with something, since the error message basically means "try again", and doesn't point to anything specific.

Best regards,

Simon

[lcj]

2.6.1

[Simonr]

Okay, please check out this ticket by Sigurd, where he explains how you can use the NVS backend for storing the device name dynamically.

Best regards,

Simon