GATT WriteLong Max Value Size

Javier Soriano

I have trying the GATT Advanced command: GATT_WriteLong and found out that the maximum value size is 96 bytes. Above this size, you get the following error response message: Too Many Prepare Writes Have Been Queued.

It was a surprise knowing that the maximum BLE attribute size is 512 bytes.

Is this a standard limitation?. a dongle hci firmware issue?.

Any way to solve it?

Thanks in advance

Javier

over 14 years ago

0 Mr. White over 13 years ago

Intellectual 255 points

The same problem and same question.

Could somebody explain this?

0 Aslak N. over 13 years ago in reply to Mr. White

TI__Mastermind 23440 points

Hi Mr,

The maximum number of Prepare Writes (GATT_MAX_NUM_PREPARE_WRITES ) on the GATT Server is set to 5 by default. And, each Prepare Write Request can carry up to 18 bytes of attribute data.

However, this max can be changed by either setting GATT_MAX_NUM_PREPARE_WRITES to a higher value in the project, or dynamically by the application using the GATTServApp_SetParameter() API.

Best regards,
Aslak

Bluetooth®︎

Bluetooth forum

GATT WriteLong Max Value Size