How to change value of descriptor?

[jokii]

Hello,

I've generated code via latest BDS and nRF51 SDK 10 plugin, and everything works OK, beside "desciptor" change. When I execute function to set value of descriptor:

ble_control_register_data_descriptor_set(&service_struct, &control_register_data_descriptor);

it returns "NRF_ERROR_INVALID_PARAM" and descriptor remain unchanged. I've checked arguments of the function and they match to declaration. in similar way, line above, I'm using also generated function for change related characteristic value:

ble_mug_control_register_data_set(&service_struct, &control_register_data);

and it works.

I can add that I'm calling this functions inside write event:

static void on_write(ble_service_t * p_service, ble_gatts_evt_write_t * p_ble_evt)

of other characteristic - I want achieve such behavior, that when client write "characteristic 1", then in "on_write", value of "characteristic 2" is evaluated as well as descriptor related to this characteristic.

I've prepared example, based on SDK10 example "experimental_bluetoothds_template", full source: experimental_bluetoothds_template_COPY.zip

www.filedropper.com/experimentalbluetoothdstemplatecopy

ble_service.c:114-118 contain code related to update descriptor value:

ble_service_control_register_data_new_descriptor_t descriptor;
uint8_t data = 0x88;
descriptor.control_register_data.size = 1;
descriptor.control_register_data.p_data = &data;
ble_service_control_register_data_new_descriptor_set(p_service, &descriptor);

Is there something I've missed, is impossible to change descriptor value in such scenario or there is other way to do this?

[Anders Strand]

I cannot access the attached file on filedropper for some reason. Can you attach a zip of the project to your question post?

[jokii]

Finally found attach file button :) File: "experimental_bluetoothds_template_COPY.zip"

[Anders Strand]

I cannnot find ble_mug_control_register_data_set nor ble_control_register_data_descriptor_set in the files you provided. In which file and what line under can i find them?

[jokii]

Sorry for misleading - ble_mug_control_register_data_set and ble_control_register_data_descriptor_set was edited by hand before I've attached example project (original source). In attached example project where I extracted problem ble_control_register_data_descriptor_set corresponds to ble_service_control_register_data_new_descriptor_setas you can see in code snippet (ble_service.c:114-118). ble_mug_control_register_data_set in example isn't present (it's work, so not included).

[Anders Strand]

Inside ble_service_control_register_data_new_descriptor_set we find

return sd_ble_gatts_value_set(p_service->conn_handle, p_service->control_register_data_new_descriptor_handles.value_handle, &gatts_value);

The attribute handle we use here (second parameter) is never set. It is given to us here In ble_service_init :

err_code = descriptor_add(BLE_GATT_HANDLE_INVALID, &control_register_data_new_descriptor, &descr_handle);

But descr handle is not saved to p_service->control_register_data_new_descriptor_handles.value_handle, &gatts_value.

I am not sure if this is a bug in BDS or the Nordic Plugin. Try replacing this in ble_service_init

err_code = descriptor_add(BLE_GATT_HANDLE_INVALID, &control_register_data_new_descriptor, &descr_handle);

with this:

err_code = descriptor_add(BLE_GATT_HANDLE_INVALID, &control_register_data_new_descriptor, &(p_service->control_register_data_new_descriptor_handles.value_handle));

Now we pass the attribute handle of the service struct, and the function descriptor_add will save the handle for us.

PS: Try to avoid naming your descriptors "New descriptor". It is very confusing to read the generated code :)