softdevice S140 v6.0.0: how to set the channel mask for different channels

[Youssif]

Hi

Can you please provide an example/pseudo-code on how the channel_mask member in the ble_gap_adv_params_t struct is used? The only examples provided in the SDK and the migration document set the entire member to {0} and it is unclear how this should used. In other words, what should we set the channel_mask to if we want to use channels 37, 38, and 39. We have tried the pseudocode below but starting advertising failed:-

s_adv_params.channel_mask[0] = 0xFF;
s_adv_params.channel_mask[1] = 0xFF;
s_adv_params.channel_mask[2] = 0xFF;
s_adv_params.channel_mask[3] = 0xFF;
s_adv_params.channel_mask[4] = 0x1F;

We are using softdevice S140 v6.0.0 and SDK 15.0.0 on an nRF52840 PDK.

Thanks

Youssif

[Sigurd]

Hi,

It is currently not supported to mask away secondary advertising channels, if you try that you will get a "NRF_ERROR_NOT_SUPPORTED" returned from sd_ble_gap_adv_set_configure(). This is what's happening in your case. If you set a bit in the channel_mask to 1, the channel is not used (masked away).

So if you want to use 37, 38, and 39 (primary advertising channels), then you don't need to set a channel mask at all. The adv_params are usually memset to 0 after declaration anyways. But you can of course set all your s_adv_params.channel_mask[x] to 0x00.

[Youssif]

OK one more question, what if I want to advertise on channel 37 but not 38 and 39, how would I set that?

Thanks

Youssif

[Sigurd]

Hi,

You could set it like this: adv_params.channel_mask[4] = 0xC0;

[Lexi]

Hi, what is the [4] means here? if I just want to advertise on 38 then how it will be look like? and can I set it like "p_advertising->adv_params.channel_mask[4] = 0xC0" in ble_advertising.c ? 

[Sigurd]

Hi Lexi,

The 40 BLE channels are each represented by 1 bit. In total there are 5 array elements (0 to 4), 8 bits for each array element. The LSB contained in array element 0 represents channel index 0, and bit 39 ( MSB in array element 4) represents channel index 39.

channel_mask[4] is therefore the 8 upper channels. If you only want to advertise on 38, you will need set bit 39 and 37 high, so that would be adv_params.channel_mask[4] = 0xA0; (1010 0000 in binary).

Using the advertising module, you could place it ble_advertising.c in the function ble_advertising_start(), right before sd_ble_gap_adv_set_configure() is called. The SDK15.0 ble_advertising_start() function would then look like this:

uint32_t ble_advertising_start(ble_advertising_t * const p_advertising,
                               ble_adv_mode_t            advertising_mode)
{
    uint32_t ret;

    if (p_advertising->initialized == false)
    {
        return NRF_ERROR_INVALID_STATE;
    }

    p_advertising->adv_mode_current = advertising_mode;

    // Delay starting advertising until the flash operations are complete.
    if (flash_access_in_progress())
    {
        p_advertising->advertising_start_pending = true;
        return NRF_SUCCESS;
    }

   memset(&p_advertising->peer_address, 0, sizeof(p_advertising->peer_address));

    if (  ((p_advertising->adv_modes_config.ble_adv_directed_high_duty_enabled) && (p_advertising->adv_mode_current == BLE_ADV_MODE_DIRECTED_HIGH_DUTY))
        ||((p_advertising->adv_modes_config.ble_adv_directed_enabled)           && (p_advertising->adv_mode_current == BLE_ADV_MODE_DIRECTED_HIGH_DUTY))
        ||((p_advertising->adv_modes_config.ble_adv_directed_enabled)           && (p_advertising->adv_mode_current == BLE_ADV_MODE_DIRECTED))
       )
    {
        if (p_advertising->evt_handler != NULL)
        {
            p_advertising->peer_addr_reply_expected = true;
            p_advertising->evt_handler(BLE_ADV_EVT_PEER_ADDR_REQUEST);
        }
        else
        {
            p_advertising->peer_addr_reply_expected = false;
        }
    }

    p_advertising->adv_mode_current = adv_mode_next_avail_get(p_advertising, advertising_mode);

    // Fetch the whitelist.
    if ((p_advertising->evt_handler != NULL) &&
        (p_advertising->adv_mode_current == BLE_ADV_MODE_FAST || p_advertising->adv_mode_current == BLE_ADV_MODE_SLOW) &&
        (p_advertising->adv_modes_config.ble_adv_whitelist_enabled) &&
        (!p_advertising->whitelist_temporarily_disabled))
    {
        p_advertising->whitelist_in_use         = false;
        p_advertising->whitelist_reply_expected = true;
        p_advertising->evt_handler(BLE_ADV_EVT_WHITELIST_REQUEST);
    }
    else
    {
        p_advertising->whitelist_reply_expected = false;
    }

    // Initialize advertising parameters with default values.
    memset(&p_advertising->adv_params, 0, sizeof(p_advertising->adv_params));

    p_advertising->adv_params.properties.type = BLE_GAP_ADV_TYPE_CONNECTABLE_SCANNABLE_UNDIRECTED;

    // Use 1MBIT as primary phy if no phy was selected.
    if (phy_is_valid(&p_advertising->adv_modes_config.ble_adv_primary_phy))
    {
        p_advertising->adv_params.primary_phy = p_advertising->adv_modes_config.ble_adv_primary_phy;
    }
    else
    {
        p_advertising->adv_params.primary_phy = BLE_GAP_PHY_1MBPS;
    }

    if (p_advertising->adv_modes_config.ble_adv_extended_enabled)
    {
        // Use 1MBIT as secondary phy if no phy was selected.
        if (phy_is_valid(&p_advertising->adv_modes_config.ble_adv_primary_phy))
        {
            p_advertising->adv_params.secondary_phy = p_advertising->adv_modes_config.ble_adv_secondary_phy;
        }
        else
        {
            p_advertising->adv_params.secondary_phy = BLE_GAP_PHY_1MBPS;
        }
    }
    p_advertising->adv_params.filter_policy = BLE_GAP_ADV_FP_ANY;

    // Set advertising parameters and events according to selected advertising mode.
    switch (p_advertising->adv_mode_current)
    {
        case BLE_ADV_MODE_DIRECTED_HIGH_DUTY:
            ret = set_adv_mode_directed_high_duty(p_advertising, &p_advertising->adv_params);
            break;

        case BLE_ADV_MODE_DIRECTED:
            ret = set_adv_mode_directed(p_advertising, &p_advertising->adv_params);
            break;

        case BLE_ADV_MODE_FAST:
            ret = set_adv_mode_fast(p_advertising, &p_advertising->adv_params);
            break;

        case BLE_ADV_MODE_SLOW:
            ret = set_adv_mode_slow(p_advertising, &p_advertising->adv_params);
            break;

        case BLE_ADV_MODE_IDLE:
            p_advertising->adv_evt = BLE_ADV_EVT_IDLE;
            break;

        default:
            break;
    }

    if (p_advertising->adv_mode_current != BLE_ADV_MODE_IDLE)
    {
        p_advertising->adv_params.channel_mask[4] = 0xA0;
        ret = sd_ble_gap_adv_set_configure(&p_advertising->adv_handle, p_advertising->p_adv_data, &p_advertising->adv_params);
        if (ret != NRF_SUCCESS)
        {
            return ret;
        }
        ret = sd_ble_gap_adv_start(p_advertising->adv_handle, p_advertising->conn_cfg_tag);

        if (ret != NRF_SUCCESS)
        {
            return ret;
        }
    }

    if (p_advertising->evt_handler != NULL)
    {
        p_advertising->evt_handler(p_advertising->adv_evt);
    }

    return NRF_SUCCESS;
}

[Lexi]

Thank you so much for such amazing explanation, I understood after a long time searching the net, just one more question, I am trying to find RSSI values based on advertising channel because the rssi values are different in each channel and save them on a log file. I am using 2 peaces of nrf52840 preview DK board and SDK 15.0 I have not found yet an example which is close to work on. would you please help me. I am trying to turn off some channels to just received RSSI based on one of them but I can not received the channel number on the receiver board.  (used bms example on transmitter board (as beacon) and central example on receiver) . really appreciate your help