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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?
Jdoe098767890
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1 Answers1

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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.

Eirik M
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    The default MTU is 20 and this value can be changed to max 512, then the GATT value can be set as 512-3 byte. use 20 bytes or less does not save power actually if you want to transfer byte more than 20. – Guo Xingmin Aug 04 '16 at 07:31