https://devzone.nordicsemi.com/f/nordic-q-a/13854/how-to-return-invalid-value-sizeHi, I want to write a characteristic, the value size is fixed, for example the size is 4 bytes. When I try to wirte 6 bytes from the client, the first 4 bytes is writed succesfully and the last 2 bytes is droped.I want users know the value size is invaliden-USTelligent Community 13Wed, 18 May 2016 14:21:12 GMThttps://devzone.nordicsemi.com/thread/52935?ContentTypeID=1Wed, 18 May 2016 14:21:12 GMT137ad170-7792-4731-bb38-c0d22fbe4515:4cbfdb57-effc-4223-87b4-a11a338960ffzhwzh308<p>Are you interested in sending status code in bluetooth? You may need to write this up and define the error codes. I was looking at <code>ble_dfu.h</code> and there are some hints in implementing this kind of tricks. If you look at this enum <code>ble_dfu_resp_val_t</code>, it is sent using <code>ble_dfu_response_send</code> function when a status needs to be reported to user.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/52937?ContentTypeID=1Wed, 18 May 2016 01:23:53 GMT137ad170-7792-4731-bb38-c0d22fbe4515:0f91798c-4097-4f88-a1d4-d940c23bc56cnrfmote<p>Thanks. If the user write the charactreistic with right size value, nothing need to report.But if the user write more than the max size of the characteristic, I want send a massage to let the user know the error. Which function I can use to send the message or response to inform the user app that the error data size has inputted?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/52936?ContentTypeID=1Wed, 18 May 2016 00:03:56 GMT137ad170-7792-4731-bb38-c0d22fbe4515:94fb8288-a47f-4bb5-8669-89f2abc92f70zhwzh308<p>You can do that, but why bother reporting error if you are proceeding with 4 bytes anyway?</p> <p>You can return error <code>NRF_ERROR_DATA_SIZE</code>, that is, error number 12.</p><div style="clear:both;"></div>