CC2642R-Q1: Maximum value of MAX_PDU_SIZE

Yoshiaki Otsu

Part Number: CC2642R-Q1
Other Parts Discussed in Thread: SYSCONFIG

hello

We implement BLE Service using SIMPLE LINK-CC13X2-26X2-SDK_6.30.01.03 and CC2642R-Q1.

We believe that since the maximum MAX_PDU_SIZE+MIC is 255Bytes, the maximum MAX_PDU_SIZE should be 251Bytes.
However, the ti_ble_config.h generated by sysconfig has the following statement

// Maximum size in bytes of the BLE HCI PDU. Valid range: 27 to 255
// The maximum ATT_MTU is MAX_PDU_SIZE - 4.

I believe this is incorrect and the maximum value for MAX_PDU_SIZE is 251.

Is there any misunderstanding?

over 2 years ago

0 Christin Lee over 2 years ago

TI__Guru 56215 points

Hi,

The maximum payload+ MIC is 255 bytes. This is the parameter used internally in our controller.

To set it to 255 means 251bytes ATT_MTU + 4 bytes MIC.

0 Yoshiaki Otsu over 2 years ago in reply to Christin Lee

Prodigy 130 points

I did not understand the explanation of ATT_MTU.
We believe the following
255Byte = 4Byte L2CAP_HDR_SIZE + 247Byte ATT_MTU + 4Byte MIC

If MAX_PDU_SIZE = ATT_MTU + 4, then MAX_PDU_SIZE = L2CAP_HDR_SIZE + ATT_MTU and MAX_PDU_SIZE should not include MIC.

If MAX_PDU_SIZE is set to 255, does it not meet the Bluetooth Core Specification?

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CC2642R-Q1: Maximum value of MAX_PDU_SIZE