How to switch between connection handles when nrf52 is connected to multiple centrals?

RE: How to switch between connection handles when nrf52 is connected to multiple centrals?

FormerMember — Mon, 27 Mar 2017 08:55:07 GMT

To map the various connection handles, you can for example use an array.

RE: How to switch between connection handles when nrf52 is connected to multiple centrals?

sijohans — Wed, 22 Mar 2017 10:15:48 GMT

Do you have a good suggestion for how to map them?

RE: How to switch between connection handles when nrf52 is connected to multiple centrals?

RK — Mon, 20 Mar 2017 21:22:15 GMT

no it's not - there's no guarantees abut the connection handle value. It might work today, it might fail dismally tomorrow with a new release. For full code compatibility you need to map them.

RE: How to switch between connection handles when nrf52 is connected to multiple centrals?

sijohans — Mon, 20 Mar 2017 14:26:37 GMT

I also have some question about this. Assume my application can handle 4 concurrent connections and i configure the softdevice for this. Will the connection handles always be in range [0:3]?

If i have a structure (this is just an example) that holds the state of a client, and have an array of these structures, is it safe to use the connection handle as index in the array?

typedef struct ble_client_s {
    volatile uint8_t     is_connected;
    volatile uint8_t     notification_enabled;
    app_fifo_t  rx_queue;
    app_fifo_t  tx_queue;
    void        *p_context;
} ble_client_t;

static ble_client_t m_ble_clients[4];

static void isr_ble_evt_handler(ble_evt_t *p_ble_evt)
{
    switch (p_ble_evt->header.evt_id)
    {
        case BLE_GAP_EVT_CONNECTED:
        {
            m_ble_clients[p_ble_evt->evt.gatts_evt.conn_handle].is_connected = 1;
        } break; /* BLE_GAP_EVT_CONNECTED */
        case BLE_GAP_EVT_DISCONNECTED:
        {
            m_ble_clients[p_ble_evt->evt.gatts_evt.conn_handle].is_connected = 0;
        } break; /* BLE_GAP_EVT_DISCONNECTED */

        /* ... */

        default:
            break;

    }
}

If this a suitable solution to hold states of the different connected clients? Or can the connection handles have other values?

RE: How to switch between connection handles when nrf52 is connected to multiple centrals?

RK — Mon, 20 Mar 2017 06:27:33 GMT

The connection handle is given to you when the device connects. You need to save it and use it later.

RE: How to switch between connection handles when nrf52 is connected to multiple centrals?

Pranay — Mon, 20 Mar 2017 06:26:16 GMT

Hi,Thanks RK when I am simply sending the data it is being received by lastly connected device,not by others...as you have mentioned in second case from where I should extract connection handle of each connected device?

RE: How to switch between connection handles when nrf52 is connected to multiple centrals?

RK — Mon, 20 Mar 2017 06:19:12 GMT

Well if the data is just a readable characteristic then there's nothing to do, you set the value, any of the connected centrals can read. if you're talking about something like notifications where you send data out proactively, those calls all take a connection handle, so just put in the connection handle of the device you want to send to.