Adding Multiple Presentation Format Descriptors

[Joshua]

The Bluetooth specification states:

If more than one Characteristic Presentation Format declarations exist, in a characteristic definition, then a Characteristic Aggregate Format declaration shall exist as part of the characteristic definition

However, there doesn't seem to be any way to add the Presentation Format descriptor except using sd_ble_gatts_characteristic_add(), which only seems to allow a single PF descriptor to be specified.

Calling sd_ble_gatts_descriptor_add() to attempt to manually add PF descriptors fails with the error code NRF_ERROR_FORBIDDEN.

Is there any way to add multiple Characteristic Presentation Format descriptors to a single characteristic?

edit: This is for a characteristic value that is comprised of 4 discrete quantities:

byte  | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |
value |  1st  |      2nd      |      3rd      |        4th        |

The 1st value is 16-bit signed integer, the 2nd-4th values are 32-bit signed integers.

[Petter Myhre]

Could you explain a bit more? Why do you need multiple descriptors?

[Petter Myhre]

Have you tried to use sd_ble_gatts_descriptor_add()?

[Joshua]

Yes, it fails with the error code NRF_ERROR_FORBIDDEN for the UUID corresponding to a presentation format descriptor.

[Hung Bui]

Hi Joshua,

Unfortunately, the feature is not supported in our current softdevices. We allow adding Characteristic Aggregate Format but not multiple Characteristic Presentation Format.

Is it possible that you split your characteristic into 4 ?

Would the format really needed to be there in the GATT or it can be hard coded in the peer side ?

[Joshua]

It can be hard-coded in the peer side, it is not really needed, I just figured it would be useful.