BLE_NUS_C_EVT_NUS_TX_EVT has handle of 0xffff

[syc776]

I have following problem:

I am using a multilink NUS Central. With one peripheral connection everything works fine. But when make a second connection I sometimes get an error when I try to send data back in received event.

In ble_nus_c_evt_handler event with event type BLE_NUS_C_EVT_NUS_TX_EVT the p_ble_nus_c sometimes has an invalid connection handle (0xFFFF).

If I try to send data back I get following warning: <warning> ble_nus_c: Connection handle invalid.

How is this possible? I am assigning the handles with  ble_nus_c_handles_assign on discovery complete.

Does anyone know about this issue?

[awneil]

syc776 said:

I am assigning the handles

Surely, the SoftDevice assigns the handle, and advises it in the 'Connected' event ?

[syc776]

yes I am assigning the handles with  ble_nus_c_handles_assign on discovery complete

void ble_nus_c_on_ble_evt(ble_evt_t const * p_ble_evt, void * p_context)
{
    ble_nus_c_t * p_ble_nus_c = (ble_nus_c_t *)p_context;

    if ((p_ble_nus_c == NULL) || (p_ble_evt == NULL))
    {
        return;
    }

    if ( (p_ble_nus_c->conn_handle != BLE_CONN_HANDLE_INVALID)
       &&(p_ble_nus_c->conn_handle != p_ble_evt->evt.gap_evt.conn_handle)
       )
    {
        return;
    }

    switch (p_ble_evt->header.evt_id)
    {
        case BLE_GATTC_EVT_HVX:
						
            on_hvx(p_ble_nus_c, p_ble_evt);
            break;

        case BLE_GAP_EVT_DISCONNECTED:
            if (p_ble_evt->evt.gap_evt.conn_handle == p_ble_nus_c->conn_handle
                    && p_ble_nus_c->evt_handler != NULL)
            {
                ble_nus_c_evt_t nus_c_evt;

                nus_c_evt.evt_type = BLE_NUS_C_EVT_DISCONNECTED;

                p_ble_nus_c->conn_handle = BLE_CONN_HANDLE_INVALID;
                p_ble_nus_c->evt_handler(p_ble_nus_c, &nus_c_evt);
            }
            break;

        default:
            // No implementation needed.
            break;
    }
}

p_ble_evt->evt.gap_evt.conn_handle=0xffff

[Edvin]

Hello,

There is a bug in ble_nus_c when you are dealing with several connections.

If you look in the ble_nus_c.c file, find the function called on_hvx. I am not sure what SDK version you use, but in SDK15.3.0 it should look like this:

static void on_hvx(ble_nus_c_t * p_ble_nus_c, ble_evt_t const * p_ble_evt)
{
    // HVX can only occur from client sending.
    if (   (p_ble_nus_c->handles.nus_tx_handle != BLE_GATT_HANDLE_INVALID)
        && (p_ble_evt->evt.gattc_evt.params.hvx.handle == p_ble_nus_c->handles.nus_tx_handle)
        && (p_ble_nus_c->evt_handler != NULL))
    {
        ble_nus_c_evt_t ble_nus_c_evt;

        ble_nus_c_evt.evt_type = BLE_NUS_C_EVT_NUS_TX_EVT;
        ble_nus_c_evt.p_data   = (uint8_t *)p_ble_evt->evt.gattc_evt.params.hvx.data;
        ble_nus_c_evt.data_len = p_ble_evt->evt.gattc_evt.params.hvx.len;
        ble_nus_c_evt.conn_handle = p_ble_evt->evt.gattc_evt.conn_handle;

        p_ble_nus_c->evt_handler(p_ble_nus_c, &ble_nus_c_evt);
        NRF_LOG_DEBUG("Client sending data.");
    }
}

So the only line that is added is:

ble_nus_c_evt.conn_handle = p_ble_evt->evt.gap_evt.conn_handle;

This line will forward the connection handle to the ble_nus_c_on_ble_evt() (which it doesn't do by default).

Best regards,

Edvin

[syc776]

now my sdk version 15.0

[syc776]

thanks your answer!

now. how to modify the code ?

[Edvin]

Did you try to implement something similar as in the previous snippet? You need to look for the place that forwards the BLE_NUS_C_EVT_NUS_TX_EVT, and add the connection handle in this event.

look in ble_nus_c.c, and search for BLE_NUS_C_EVT_NUS_TX_EVT. 

Add this line:

ble_nus_c_evt.conn_handle = p_ble_evt->evt.gattc_evt.conn_handle;

before:

p_ble_nus_c->evt_handler(p_ble_nus_c, &ble_nus_c_evt);