Characteristic Value Read

RE: Characteristic Value Read

run_ar — Tue, 06 Feb 2018 14:06:01 GMT

This should probably have been a separate question...

RE: Characteristic Value Read

puff — Mon, 22 Jan 2018 01:25:06 GMT

what if location_for_my_value is an array of 16 values of uint8_t?

i set the temp.len to 16, but whenever I printf the resulted array, I get the same values all the time, which seem to be addresses, not the actual data.

RE: Characteristic Value Read

FormerMember — Fri, 17 Jun 2016 11:32:54 GMT

In order to make sure that you get/read the correct value, temp.len should be set to the number of bytes that you want to read.

RE: Characteristic Value Read

Sascha — Thu, 16 Jun 2016 12:17:01 GMT

Ok, i dont know why, but after i erased Region 0(SD) and Region 1(APP) and flashed it again it's running correctly. :) thx!!

RE: Characteristic Value Read

Sascha — Thu, 16 Jun 2016 10:12:14 GMT

Hi Kristin, thank you. I think, i now understand this function with the ble_gatts_value_t struct. So i have changed my code to yours. When i run this code, after the sd_ble_gatts_value_get() the "location_for_my_value" value should contain the value from the characteristic!? But even when i change the characteristic value to AA-AA-AA-AA-AA, the "location_for_my_value" contains 0x00 from memset() :-/

RE: Characteristic Value Read

FormerMember — Thu, 16 Jun 2016 08:39:38 GMT

ble_gatts_value_t is defined the following way:

typedef struct
{
  uint16_t  len;       
  uint16_t  offset;    
  uint8_t   *p_value;   
} ble_gatts_value_t;

In your example, in order to make temp contain the value of the attribute after calling sd_ble_gatts_value_get(), p_value in ble_gatts_value_t has to be set to point to a location:

uint8_t location_for_my_value;


temp.p_value   = &location_for_my_value;
temp.len      = number_of_bytes_you_want_to_read;
temp.offset   = 0;
err_code = sd_ble_gatts_value_set(BLE_CONN_HANDLE_INVALID, 0x000E, temp);

To make the code more robust, I would recommend you to refer to the reference for the attribute handle value, rather than hard code the handle value. For retrieving the battery level value in the ble_app_hrs example in the SDK, it would be the following:

err_code = sd_ble_gatts_value_set(m_conn_handle,m_bas.battery_level_handles.value_handle, temp);

RE: Characteristic Value Read

Sascha — Wed, 15 Jun 2016 13:24:41 GMT

Hi Wojtek, ok that was really embarrassing, i changed it. Now no error occurs. But when i view at temp, i only get an empty p_value 0x00000000 with the correct len of 0x0005 (5Bytes)!?

RE: Characteristic Value Read

Wojtek — Wed, 15 Jun 2016 12:49:00 GMT

0x00000010 = NRF_ERROR_INVALID_ADDR, which for function sd_ble_gatts_value_get means that Invalid pointer supplied. Temp is only the pointer to the ble_gatts_value_t, but where physically is that value stored? Please try changing temp type to ble_gatts_value_t (instead of ble_gatts_value_t*)...