How to access the Device Name Characteristic

RE: How to access the Device Name Characteristic

Krishna Shingala — Wed, 16 Apr 2014 09:54:08 GMT

Hi Julian,

As Balaji recommends using PStorage module in SDK can help you store the device name persistently.

PStorage module is currently used to store bonding information in persistent memory (flash on nrf51 devices). What you can do to be able to store your data is register with the module using the pstorage_register API. Note that in pstorage_platform.h for your example, increase the number of applications by 1 in order that the API succeeds. You can request 1 block of maximum_size you wish to permit for your device name. Please note that BLE_GAP_DEVNAME_MAX_LEN limits the device name to be set locally, hence this may be a consideration to chose the maximum limit.

On success of this API, you will get a reference 'handle' to the persistent memory where you can store device name. Using this handle you can store and load data when you like using pstorage_store and pstorage_load functions respectively. I recommend you read PStorage documentation before getting started.

Things to consider: a. You may want to store the length of local device name along with the name instead of relying in null terminated strings to be to support variable length device name with errors. b. When registering with the PStorage module, remember that you request only multiples of 4, therefore, if you wish to maximum limit the device name to 31, you will have to request a block of size 32. c. One entire flash page of size 1024 will be reserved even if you request 1 block of size 32.

Hope this helps!

Regards, Krishna

RE: How to access the Device Name Characteristic

Juliane — Wed, 16 Apr 2014 09:24:31 GMT

Hi Balaji,

It is the best way to solve my problem,but I don't know how can I achieve that,is there any example for my problem?

Thanks! Juliane

RE: How to access the Device Name Characteristic

Balaji Srinivasan — Wed, 16 Apr 2014 09:15:43 GMT

Hi Juliane,

Once the IOS app writes to the Device Name characteristic, you will have to store it in flash at a predefined location. Each time the app starts up (from System Off mode), it should read that location and advertise with that device name. You can use the pstorage module included in the SDK to do the flash operation.

Does it answer your question?

Cheers, Balaji

RE: How to access the Device Name Characteristic

Juliane — Wed, 16 Apr 2014 07:23:31 GMT

Hi Balaji,

If I want to chang the device name by an IOS APP ,how can I do with my application ble_app_hrs?

I am looking forward to your reply. Thanks!

RE: How to access the Device Name Characteristic

Juliane — Wed, 16 Apr 2014 06:48:29 GMT

Hi Joe,

I want to chang the device name by a central app,and next time ,device advertise the changed name .how can i achive that ,and could you share the solution with me?

thanks!

RE: How to access the Device Name Characteristic

Balaji Srinivasan — Mon, 03 Mar 2014 12:25:36 GMT

Yes. It is a good idea to check the 'type' as well.

RE: How to access the Device Name Characteristic

Joe Merten — Mon, 03 Mar 2014 12:17:35 GMT

Yep, that works!

But I have to access to char_uuid.uuid. Should I also check for char_uuid.type == BLE_UUID_TYPE_BLE or is that not necessary?

Regarding write.data: That data array isn't zero terminated right? That's the reason why I also have to consider write.data.

Funny: I can set a device name that includes zero bytes. And Utf-8 looks well supported e.g. in Android nRF MCP: $ gatttool -b C2:73:79:CE:FC:0E --char-write --handle=0x0003 --value=48616C6C6F20F09F988E

RE: How to access the Device Name Characteristic

Balaji Srinivasan — Mon, 03 Mar 2014 10:00:41 GMT

Hi Joe,

@TODO JM: is there a better way?

The UUID of the Device name characteristic is 0x2A00. So you can do something like this..

[i]if (p_ble_evt->evt.gatts_evt.params.write.context.char_uuid == BLE_UUID_GAP_CHARACTERISTIC_DEVICE_NAME) [/i] instead of

if (p_evt_write->handle == 3)

The macro BLE_UUID_GAP_CHARACTERISTIC_DEVICE_NAME is defined to 0x2A00 in ble_types.h.

@How to access the Device Name

You can retrieve the device name from the field p_ble_evt->evt.gatts_evt.params.write.data. The length of the device name will be in p_ble_evt->evt.gatts_evt.params.write.len.

Hope this helps.

Cheers, Balaji