device length about sd_ble_gap_device_name_set

[MrFine]

Hi I use SDK 12.3 and sdk 2.0.1 , and set a device name length is 21 like "1234567890ABCDEFGHIJK" by sd_ble_gap_device_name_set; but in the advertise data the name length is only 18 and the name is "1234567890ABCDEFGH" ;

and on Android Phone display name is "1234567890ABCDEFGH", length 18; but on iOS Phone is "1234567890ABCDEFGHIJK" length 21;

so I don`t know which one is right , and why lost 3 octets name?

[Bjørn Kvaale]

It seems Android and iPhone have different maximum device name lengths. As this case shows, the max advertising packet length is 31 bytes. If you need to advertise more data, you can use the scan response packet (see link). If your name is too long, you can get a data size limit error. But I would advise you to use a shorter name. That way, it is easier for you identify on different devices and you use up less advertising packet space.

[MrFine]

I get the data in the air, it is really 18 data name, I can set a shorter name,but I want know why can`t set a longer name, the descripter of sd_ble_gap_device_name_set() said must be smaller or equal than BLE_GAP_DEVNAME_LEN (31), so why the length large than 18 will be shorted?

[Bjørn Kvaale]

Take a look at the answer to this case. In the 31 bytes you have available to send in each packet, you have the device name field, a flag field, a 16-bit service class UUID and manufacturer specific data. So you cannot use all of the 31 bytes to set as your device name. The other values also need to be initialized and sent in the same packet.

[MrFine]

May be this lead the issue, but why it don`t return error while I set the advertise data or device name ?

[Bjørn Kvaale]

I don't quite understand. Do you expect an error when you set the device name? Do you mean if you set a device name longer than 18 bytes?