CC2340R5: How to enable mulitple notification

Hi,

To clarify, you are trying to identify from the central side which attribute a received notification belongs to?

Best Regards,

Jan

NO. I am talking of peripheral end.When peripheral receives CCCD write to enable notification there is ONE switch case statement in write callback

case GATT_CLIENT_CHAR_CFG_UUID:. Under this case statement notification will be enabled.

Please refer to simple_gatt_service.c

Function : SimpleGattProfile_writeAttrCB

Snippet of notification enabling code

case GATT_CLIENT_CHAR_CFG_UUID:
status = GATTServApp_ProcessCCCWriteReq( connHandle, pAttr, pValue, len,
offset, GATT_CLIENT_CFG_NOTIFY );
//notify the App that a change has occurred in Char 4
notifyApp = SIMPLEGATTPROFILE_CHAR4;
break;

If you have ONLY one attribute then we can have the above code, but when we have mutiple ( more than ONE attribute ) how to enable notification

for each attribute individually?. Or at this point how to identify which attributes CCCD is being enabled by central device?

Hi Manjunath, 

Thanks for the details above!

For this, it will fall under one case because the UUID (0x2902 which is defined in the Bluetooth specification) is always the same. You only need to add a new characteristic in the GATT table and there's no further code modification to enable this notification. Please refer to our data_stream SLA for more details on attributes and characteristics.

Regards

Ivan

Hi Ivan,

    Thanks for reply.

I have added a new characteristics. I want to enable notification. When i enable notification button in SimpleLink app in central ( mobile ) how do i know which attribute notification is enabled?

Ex: If i have attribute A and B , if central device enables notification for B, how do i know Notification for B is enabled, so that i can send notification immediately 

Line number 588 simple_gatt_profile.c has following code

notifyApp = SIMPLEGATTPROFILE_CHAR4;  

This code send notification immediately on enabling notification on central device.

In this example there is ONLY ONE attribute so no worry, when i have more than ONE attribute how to decide which attribute notification was enabled

Hi Manjunath, 

The GATT Client needs to write to each CCCD individually so it will enable the notification for a particular characteristic, it simply uses a write request ATT packet to set the corresponding bit to 1. The server will then reply with a write response and start sending the appropriate packets whenever it wants to alert of change in value. Each characteristic requires a CCCD if it needs to support a Notify and/or Indicate. You make the API call based on per-characteristic basis. 

Please see example below from the User's guide: 

Handle 0x002D contains the CCCD. The UUID for the CCCD is always the standard 0x2902 as previously mentioned. The CCCD must always be readable and writable, by writing to this attribute writing 0x0001, a GATT server can configure for notifications. writing 0x0002 for indications or writing 0x0000 disable notifications and indications.

I hope this helps. 

Regards

Ivan

No it didn't helped me.

Looks you didn't got my question.

I know GATT client writes to each attribute individually and also enable CCCD inidividually by writing 1 to it.

How do server know which attributes notification is enabled as UUID 0x2902 is used for all attributes.

Again Iam trying to explain the same example

Assume i have two attributes A & B, all required things is taken care

Now when GATT client enable notification below code will get executed in GATT server

case GATT_CLIENT_CHAR_CFG_UUID:
status = GATTServApp_ProcessCCCWriteReq( connHandle, pAttr, pValue, len,
                                                                              offset, GATT_CLIENT_CFG_NOTIFY );

whether it is attribute A or B or C or D, you agree?

Now here how do i know which attributes ( A/B/C/D ) notification is enabled

Hi Ivan,

   Did you get chance to look into this?

Hi Clement,

  Thanks for reply.

gattAttribute_t structure is of following type

typedef struct attAttribute_t
{
gattAttrType_t type,           //!< Attribute type (2 or 16 octet UUIDs)
uint8 permissions;              //!< Attribute permissions
uint16 handle;                    //!< Attribute handle - assigned internally by attribute server
uint8* const pValue;             //!< Attribute value - encoding of the octet array is defined in
                                            //!< the applicable profile. The maximum length of an attribute
                                            //!< value shall be 512 octets.
} gattAttribute_t;

In the above structure I can take "handle" for identifying the attribute. But i am not able to relate the value in receive in "handle"

to UUID.

Could you point to me how UUID is mapped to "handle" ?

Thanks

How can i use BTool in my code?

Any way i found the way to do.

Thank you

Hi,

In Ivan's suggestion, BTool is run on a second device. BTool is used to connect the device and discover its GATT table. 

If needed, you'll find the BTool user's guide here: https://software-dl.ti.com/lprf/simplelink_cc2640r2_sdk/1.30.00.25/exports/docs/blestack/btool_user_guide/BTool_Users_Guide/index.html

I hope this will help,

Best regards,

Awesome! Thank you for confirming.

Best of luck for the next steps of your project.

Kind regards,