Unable to obtain CPF descriptor handle from my custom characteristic

[Beldramma]

Hi guys !

I am working on SDK 15.2 and I have created a custom service thanks to this tutorial : https://github.com/NordicPlayground/nRF5x-custom-ble-service-tutorial

I have one characteristic, and I want to change the Presentation Format Descriptor after the initialisation of the Service so I need its handle to do that with sd_ble_gatts_value_set, but sd_ble_gatts_descriptor_add returns only four handlers and there is not the CPF. 

I have tried to get this handler with descriptor_add from the ble_srv_common.c library, but it returns NRF_ERROR_FORBIDDEN. 

From the documentation, we have this error message if "Forbidden value supplied, certain UUIDs are reserved for the stack."

So it means that we cannot obtain this handle and modify the CPF handler ? Is there another way to do that ?

Thanks for your answers,

Regards

Beldramma

[Amanda Hsieh]

Hi Antoine, 

Try to add it with sd_ble_gatts_characteristic_add(), not sd_ble_gatts_descriptor_add(). See this thread. 

Please let me know how it works.

-Amanda H.

[Beldramma]

Hi Amanda,

Ihave already done that but sd_ble_gatts_characterisitic_add returns only four descriptor handles which are : 

• value handle
• user desc handle
• cccd handle
• sccd handle

and not the cpf hanlde. What i want to do is to initialize it when i create my characteristic but sometimes also change its value, that's why I need its handle. 

Regards,

[Beldramma]

Any News ?

[Amanda Hsieh]

Hi Antoine, 

Sorry for the delay.  

Beldramma said:

and not the cpf hanlde. What i want to do is to initialize it when i create my characteristic but sometimes also change its value, that's why I need its handle. 

 I don't think it's possible.

-Amanda H. 

[Beldramma]

Weird, why all the SIG-adopted descriptors are not included in the ble_gatts_char_handles_t structure ? 

[Beldramma]

Do you know how handles are generated ? If yes, maybe there is a way to obtain the CPF handle like that. 

I have read this topic, they talk about that. Can you tell me if this subject can help me ?