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BlueNRG-MS v7.2c Central is not receiving ADV_IND & SCAN_RSP > 18 bytes - why it cannot receive up to MAX_ADV_DATA_LEN?

Question asked by Scott Lohr on May 12, 2018

Hello - wrt the maximum total size of a BLE advertisement or scan response of 31 bytes:

The BlueNRG-MS v7.2c Peripheral can generate either at max expected length.

But when I run the BlueNRG-MS v7.2c Central, if the total length of either packet is > 18 bytes, then the corresponding ADV_IND or SCAN_RSP event is never received as a EVT_LE_ADVERTISING_REPORT event.

 

The Central device of the embedded BLE stack of the 3 other vendor platforms I have evaluated can all receive up to the maximum total length of either the advertisement or scan response in addition to the BLE stacks on the iOS and Android devices.

 

Is this observation caused by an error in my implementation of the ST BlueNRG Central, or is it a known and documented limitation? It is suspicious that the BlueNRG-MS Peripheral can produce either at the max length of 31 bytes, but the Central is limited to 18 bytes total. Even more suspicious is that the observed limit of 18 is less than a full length Notification of 20 bytes, which my implementation of the BlueNRG Central can receive once connected.

 

To be sure, bluenrg_gap.h contains this constant:

#define MAX_ADV_DATA_LEN                        (31)

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