CC2541: implementing central device for receiving notifications from keyfobdemo using simplekeys service

Athul P Satheesan

Part Number: CC2541

Hi,

i want to design a central device using CC2541 which acts as the GATT client for Keyfobdemo project. i was able to connect the keyfob with the central device to peripheral device. what should i do next inorder to receive key press/release notifications from the keyfob?

over 7 years ago

0 Marie H over 7 years ago

TI__Guru* 82341 points

Hi Athul,

This is described in the Sample Applications Guide, Chapter 12.1.4.

0 Athul P Satheesan over 7 years ago in reply to Marie H

Intellectual 710 points

Hi,
i referred the document but not clear about how to implement the same. Getting GAP_LINK_ESTABLISHED_EVENT means that the connection is established. right?

0 Marie H over 7 years ago in reply to Athul P Satheesan

TI__Guru* 82341 points

Hi,

GAP_LINK_ESTABLISHED_EVENT comes when a connection is established.

One way of implementing this on the central side is
1) The central must discover the Key Service. You can implement this the same way as discovering simple_gatt_service (see GATT_DiscPrimaryServiceByUUID() in simpleBLEcentral)
2) When you have discovered the service you must store the handle (see simpleBLEGATTDiscoveryEvent() in simpleBLEcentral)
3) Finally you can use the handle to write to the clientCharCfgUUID. Use e.g. GATT_WriteCharValue().

0 Athul P Satheesan over 7 years ago in reply to Marie H

Intellectual 710 points

Hi Marie,
thanks for the reply.
where do i get the service uuid for simplekeys?

0 Marie H over 7 years ago in reply to Athul P Satheesan

TI__Guru* 82341 points

Hi Athul,

The service uuid is defined in simplekeys.h:

// SK Service UUID
#define SK_SERV_UUID                  0xFFE0

0 Athul P Satheesan over 7 years ago in reply to Marie H

Intellectual 710 points

hi,
if GATT_DiscPrimaryServiceByUUID returns success, how can i get the handle?

0 Marie H over 7 years ago in reply to Athul P Satheesan

TI__Guru* 82341 points

Hi Athul,

If the return status from this function is SUCCESS, the calling application task will receive multiple OSAL GATT_MSG_EVENT messages. The type of the messages will be either ATT_FIND_BY_TYPE_VALUE_RSP or ATT_ERROR_RSP (if an error occurred on the server).

The ATT_FIND_BY_TYPE_VALUE_RSP event is defined with the following members:
attFindByTypeValueReq_t:
uint16 startHandle
First requested handle number (must be first field).
uint16 endHandle
Last requested handle number.
attAttrBtType_t type
2-octet UUID to find
uint8 len
Length of value.
uint8 * pValue
Attribute value to find (0 to ATT_MTU_SIZE-7).

0 Athul P Satheesan over 7 years ago in reply to Marie H

Intellectual 710 points

Hi Marie,
thanks for the reply.
I'm not getting any OSAL GATT_MSG_EVENT messages.

0 Marie H over 7 years ago in reply to Athul P Satheesan

TI__Guru* 82341 points

Hi Athul,

Can you use a sniffer to make sure that the packets are sent over the air?

0 Athul P Satheesan over 7 years ago in reply to Marie H

Intellectual 710 points

hi,
the process reaches:
// Service found, store handles
if ( pMsg->method == ATT_FIND_BY_TYPE_VALUE_RSP &&
pMsg->msg.findByTypeValueRsp.numInfo > 0 )
what is to be done next? how to write to GATT_CLIENT_CHAR_CFG_UUID ?

0 Marie H over 7 years ago in reply to Athul P Satheesan

TI__Guru* 82341 points

Hi Athul,

When you have the handle of the CCFG characteristic, you can write to it to enable notifications.

0 Athul P Satheesan over 7 years ago in reply to Marie H

Intellectual 710 points

Hi Marie,

thanks for the reply.

is there any difference between writing with service's connection handle and characteristic's connection handle? should i use client characteristic uuid?

Can i hardcode the client char cfg value in the gatt server itself? i cannot use sniffer because i am using a cc debugger.

0 Marie H over 7 years ago in reply to Athul P Satheesan

TI__Guru* 82341 points

Hi Athul,

Yes you have make sure to use the characteristic's connection handle, not the service handle and not the UUID. You have to do the Characteristic discovery process to comply with the Bluetooth Core Spec, so you can't hardcode the handle.

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CC2541: implementing central device for receiving notifications from keyfobdemo using simplekeys service