BLE NUS CENTRAL not ready for comms after receiving BLE_NUS_C_EVT_DISCOVERY_COMPLETE

[veletron]

Hi

I have a modified version of the BLE_NUS Central sample which connects to my production board for production test purposes.

All works fine, and Rx and Tx comms passed to/from the UART to the RX and Tx characteristics of the custom service running on my peripheral.

My issue is that after the central gets BLE_NUS_C_EVT_DISCOVERY_COMPLETE, if I immediately try to perform a GATT_Write on the peripherals RX characteristic, the Central Hangs

 ble_gattc_write_params_t const write_params =
    {
        .write_op = BLE_GATT_OP_WRITE_CMD,
        .flags    = BLE_GATT_EXEC_WRITE_FLAG_PREPARED_WRITE,
        .handle   = p_ble_nus_c->handles.nus_rx_handle,
        .offset   = 0,
        .len      = length,
        .p_value  = p_string
    };

    return sd_ble_gattc_write(p_ble_nus_c->conn_handle, &write_params);

If I run the exact same code a fraction of a second later, it succeeds.

After connection and discovery of my service (and after setting up Notify for the RX and TX characteristics), I need to inform my peripheral who it was that just connected - in this case 'ProductionTestBoard' 0x07. I do this via a protocol structure I use everywhere else in the product.

My question is, can I test wait for any other event, or test the softdevice to wait until it REALLY HAS connected to my peripheral? I tried the usual 'sleep' before the gattc_write to no avail.

Nigel

[Vidar Berg]

Hi Nigel,

Could you try to check the return code from sd_ble_gattc_write() when it fails? The connection is established and the services should have been discovered at this point so not sure why it fails. Possible return values copied from the API documentation:

* @retval ::NRF_SUCCESS Successfully started the Write procedure.
* @retval ::BLE_ERROR_INVALID_CONN_HANDLE Invalid Connection Handle.
* @retval ::NRF_ERROR_INVALID_STATE Invalid Connection State.
* @retval ::NRF_ERROR_INVALID_ADDR Invalid pointer supplied.
* @retval ::NRF_ERROR_INVALID_PARAM Invalid parameter(s) supplied.
* @retval ::NRF_ERROR_DATA_SIZE Invalid data size(s) supplied.
* @retval ::NRF_ERROR_BUSY For write with response, procedure already in progress. Wait for a @ref BLE_GATTC_EVT_WRITE_RSP event and retry.
* @retval ::NRF_ERROR_RESOURCES Too many writes without responses queued.
* Wait for a @ref BLE_GATTC_EVT_WRITE_CMD_TX_COMPLETE event and retry.
* @retval ::NRF_ERROR_TIMEOUT There has been a GATT procedure timeout. No new GATT procedure can be performed without reestablishing the connection.