What is the length limit for BLE characteristics?

bluetooth-lowenergy characteristics
Jdoe098767890 picture Jdoe098767890 · Aug 3, 2016 · Viewed 10.8k times · Source

I am reading the Bluetooth Core Spec. v 4.2 document, but I can't find any information about the characteristic length limit.

  • What is the length limit for characteristic of BLE services?

Answer

Eirik M picture Eirik M · Aug 3, 2016

The limit is set by what is possible for an attribute value, see the ATT part (Vol 3, Part F, 3.2.9):

The maximum length of an attribute value shall be 512 octets.

You should also consider what could be sent in one packet, which is 20 bytes (ATT_MTU - 3). With 20 bytes or less you can use simple transfer procedures and save power.

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