CC2540/41 Maximum length for device name attribute

Sean,

Thank you very much for your prompt response!

BR,
Jaakko

Hi,

Now I was able to actually test this with CC2541DK-MINI and by using the sample projects KeyFob and SimpleBLEPeripheral. Unfortunately, I am still having some troubles while changing the name. I am trying to change the device name that is visible to other Bluetooth devices that are scanning BT devices in the area.

I have tried changing the previously mentioned definitions in both projects incrementally up to the maximum 248 octets:
#define GAP_DEVICE_NAME_LEN (20+1)
static uint8 attDeviceName[GAP_DEVICE_NAME_LEN] = "TI BLE Keyfob";

Unfortunately this does not seem to change the name that I want. I also verified this multiple times with multiple different devices as I noticed that there has been a case in which an external BT device did not refresh the updated name for some reason:
https://e2e.ti.com/support/wireless_connectivity/f/538/t/360540

Perhaps I am doing something wrong with the attDeviceName definition, but according to the linked discussion, it seems that the device name I want to change is defined in the following array (simpleBLEPeripheral.c):

// GAP - SCAN RSP data (max size = 31 bytes)
static uint8 scanRspData[] = ...

I verified that this changes the visible name. However, according to the comment (and my own tests) it seems that the array length is limited to 31 bytes which limits also the device name length.

Now, my question is: Is it possible to increase the array size limit, and how?

Ultimately my goal is just to find out what is the easiest way to define longer (as long as possible) name for the device that can be discovered by other BT devices, such as mobile phones. So the solution does not necessarily have to be this array definition approach.

Best regards,
Jaakko

Thank you again for your quick response.

The application is a system in which Bluetooth beacon is used to advertise information (such as name and contact information) to mobile devices. This data string is easily very long.

Mobile devices are typically mobile phones or tablets having Bluetooth 4.0. It has been verified that the concept is working with this kind of mobile devices - it is possible to write the information to the 248 character long Bluetooth “Friendly name” field and once BT is “turned on” other devices are able to read the Friendly name.

The goal is to implement the same functionality with a Bluetooth beacon. It should be possible to ”program” Bluetooth beacon's ”Friendly name” with some mechanism, preferably over the air, and make the beacon advertise the name to other devices. No pairing, no voice, no other data (sensor values etc.) are needed. Just advertising of the "Friendly name".

Or maybe you could propose other suitable chipset – e.g. is there any benefit in cc256x family over the cc2541?

BR,
Jaakko

Jaakko,

Thank you, that gives me a clearer picture of your issue. It sounds like you are trying to implement a BLE connectable beacon. This is possible using the CC2541. Take a look at this app note which explains beacon implementation on the CC254x. www.ti.com/.../swra475.pdf

The limitation here is in the BLE spec. The BLE spec defines that the maximum size of an advertising packet is 31 bytes. There is a lot of information you can fit into this advertisement data packet, for example, the Google eddystone spec works within this packet to transmit telemetry, URLs, and ID information
(https://github.com/google/eddystone/blob/master/protocol-specification.md)

In summary, the length of the device name attribute can be up to 248 bytes, but only a shorter device name can be included in advertisements. This is not a limitation of the chip, but rather a rule imposed by the spec.

OK, thank you very much again.

So the limitation comes directly from the BLE specification. However, you said that this is not limitation of the chip. So I guess my final question is that do you know if there is some "non-BLE-compliant" way to achieve the long advertisement using CC254x (or CC256x)? As it seems that Bluetooth itself supports longer names, since they work with the mobile devices described earlier.

BR,

Jaakko