[TW#13711] BLE GATT Client: More than 3 connected peripherals

[lucashutch]

When trying to setup the GATT_Client to have more than 3 connected peripherals, the error ESP_GATT_NO_RESOURCES reported back when trying to add the 4th profile.

esp_ble_gattc_app_register(PROFILE_A_APP_ID);
esp_ble_gattc_app_register(PROFILE_B_APP_ID);
esp_ble_gattc_app_register(PROFILE_C_APP_ID);
esp_ble_gattc_app_register(PROFILE_D_APP_ID);

I have had a brief look into this. It seems that the limitation is in the file bta_gattc_int.h. In this file there are the definitions:

#ifndef     BTA_GATTC_CL_MAX
#define     BTA_GATTC_CL_MAX    3 // 32
#endif

/* max known devices GATTC can support */
#ifndef     BTA_GATTC_KNOWN_SR_MAX
#define     BTA_GATTC_KNOWN_SR_MAX    3 // 10
#endif

I have found that increasing these to 7 (the max number of ACL connections that is configurable using make menuconfig) fixes the issue and allows the 4th profile to be added. I have not done extensive testing with this yet, however it seems strange that the max ACL connections can be set to 7 if the gatt_client cant set up enough profile handlers to deal with them.

Please let me know if there is more information needed.

[Weijian-Espressif]

@lucazader The default maximum of register profile is 3, you can modify the value for register more profiles. By the way , register one profile can also handle multiple connections.

[FayeY]

Hi @lucazader , did the above suggestion help you resolve the issue?

[lucashutch]

hi @FayeY

Yes changing the value seems to have helped. I can now register more then 3. I also see there is a commit for the v3.0 release that will address this issue.

@Weijian-Espressif I have not yet tried handling multiple connection using one profile. Can you explain how this can be achieved?

[Weijian-Espressif]

@lucazader In one profile, different device have different conn_id. This method may be complicated to deal with. if you have enouch ram, you can register multiple app_id . it is simple to handle the connection event.

[lucashutch]

Hi @Weijian-Espressif

Thanks for the advice. I am currently already doing a similar method, using the gatt_if instead of the conn_id. I had found that there was one instance where gatt_if was present but conn_id was not in a callback somewhere. I will have more of a look into this.

Thanks for the advice!

[Weijian-Espressif]

@lucazader you could get the conn_id in the open event. /**

• @brief ESP_GATTC_OPEN_EVT / struct gattc_open_evt_param { esp_gatt_status_t status; /!< Operation status / uint16_t conn_id; /!< Connection id / esp_bd_addr_t remote_bda; /!< Remote bluetooth device address / uint16_t mtu; /!< MTU size / } open; /!< Gatt client callback param of ESP_GATTC_OPEN_EVT */

[FayeY]

Hi @lucazader , did the above suggestion help you resolve the issue?

[lucashutch]

Hi,

Yes this can be marked as solved for now.