https://devzone.nordicsemi.com/f/nordic-q-a/82557/master-slave-communication-problemI have a master device and a slave device. The slave device has 6 characteristics, 4 of which are notif. I need to use the master device to obtain the data of these 4 characteristics. I use the directory under \examples\ble_central\ble_app_uart_c Foren-USTelligent Community 13Thu, 09 Dec 2021 07:48:02 GMThttps://devzone.nordicsemi.com/thread/342630?ContentTypeID=1Thu, 09 Dec 2021 07:48:02 GMT137ad170-7792-4731-bb38-c0d22fbe4515:779cec2d-835c-4145-8bb9-2e5a4bf31bb9Einar Thorsrud<p>Hi,</p> <p>Your&nbsp;ble_nus_c_tx_2_notif_enable() calls&nbsp;cccd_configure() which in turn calls&nbsp;sd_ble_gattc_write(), and this must be where the return value 17 comes from. This is&nbsp;NRF_ERROR_BUSY, and is returned when a procedure is already in progress. That is the case here, as you called&nbsp;ble_nus_c_tx_1_notif_enable() immediately before this. The solution is to do as described in the API documentation for&nbsp;sd_ble_gattc_write: &quot;<em>For write with response, procedure already in progress. Wait for a @ref BLE_GATTC_EVT_WRITE_RSP event and retry.</em>&quot;</p><div style="clear:both;"></div>