how to use HANDLE RANGE correctly for Multiconnection ?

[Oleg]

good time dear Engineers!

Please explain how to use correctly HANDLE RANGE in functions of discovering. I use CENTRAL with up to 8 possible connections to PERIPH, so pls explain following:

sd_ble_gattc_primary_services_discover(conn_handle, start_handle, &uuid);

WHAT IS start_handle if 8 Active Connections co-exist ? why it is always 0x0001 ?

sd_ble_gattc_characteristics_discover(conn_handle, p_handle_range);

WHAT is p_handle_range if 8 ACTIVE CONNECTIONS ? for example, for 2 connections: if conn_handle1=0x0 and conn_handle2=0x1 ?

sd_ble_gattc_descriptors_discover(conn_handle, p_handle_range);

for different connections handles (0x0,0x1,etc..), must p_handle_range be different too ? e.g.

conn_handle1=0x00: p_handle_range  = {0x10,0x15}
conn_handle2=0x01: p_handle_range  = {0x20,0x25}

etc.. ?

How to Manage Handle Ranges in case of Disconnecting -> Connencting -> Discovering again , etc... correctly (in this cases old handles must be re-assigned again) ?

I have one SERVICE (1666) two CHAR's (d5aa, d780) in this service and 4 Descriptors in each CHAR.

I found SERVICE, CHARS and store it's HANDLEs in my database according to the Photo. Q: how to find all descriptors in each CHAR's ? What valid handle_range I should use as PARAMETER to sd_ble_gattc_descriptors_discover(...) ?

if I use handle_range of [e.g. 0x09 - 0x0E] means from service start_ handle to last char handle_value , seems it's OK, all the Attribute founds success.

[Hung Bui]

Hi Oleg,

First, we need to clarify the conn_handle and the start_handle/p_handle_range they are completely unrelated.

start_handle/p_handle_range has nothing to do with your number of peripheral connection.

start_handle/p_handle_range is the handle ID in the attribute table. The attribute table is where the services, characteristics are located each of them has a handleID.

The service discovery process (discovering primary services, characteristics) requires a handle ID range to work it. Basically it tell from where to where in the attribute table you are asking the server to reply what is the service and characteristic inside. You can have a look at section 4.4 and 4.6 at Vol 3 Part G in the Bluetooth Spec v4.2

This handle ID is local for a specific server (usually on peripheral).

Note that when you request for a service discovery from handle A to handle B, you may not receive all the primary services at once. The server may return with 1 or 2 services. You need to repeat discovery the service from the end handle of the last service to the last handle (handle B).

I would strongly suggest to have a look at our database discovery library.

[Oleg]

dear Hung Bui. I checked db_discovery before and also 4.4-4.6 spec 4.2.

according to 4.6.1(2) and my photo above , I found all the PAIRs of Attribute Handle and Value=(prop/handl,uuid) continously (new_start_handle = last_attr_handle+1). But. if I use sd_ble_gattc_descriptors_discover(...) w argument handle_range, what range I should use ?

for example, I already have an array (db) with handle_values I found use char. discovering (as in 4.6.1):

connection[0].service[0].char[0].handle_decl =0x000a; // to acces for ??????? what ? connection[0].service[0].char[0].handle_value=0x000b; // to acces for read/write operations. connection[0].service[0].char[1].handle_decl =0x000d; connection[0].service[0].char[1].handle_value=0x000e;

and I want to found all the descriptions for char[0] / char[1] , what argument of sd_ble_gattc_descriptors_discover() should use ?

also one question about handle_decl , I dont found how it use for ?