BLE payload data length bigger than 20 bytes not registering any event.

[gamli]

Hello,

I am having some problems with sending data packets larger than 20 bytes over BLE.

We are currently updating our product, that includes the nRF52832 on a custom board and using SDK v13.0.0 and soft device s132 v4.0.2. We are updating to SDK 17.0.2 and s132 v7.2.0. To test the connection I am using an nRF52840 dongle and the nRF Connect standalone v4.0.4.

I have successfully updated our device and gotten a stable connection using SDK 17.0.2. I have been able to use the 2Mbps PHY and updated data length on the connection to be 251 bytes. I have made all changes to the SDK config that I believe have any impact on this (set GAP Data length to 251 and Max MTU size to 293 and increased GAP event length). The issue appears when I attempt to send data packets to the device that are bigger than 20 bytes. The device does not trigger any interrupt and no event is registered, and no warning or error either. The connection is still stable and working.
When sending smaller data packets, the SD_EVT_IRQHandler is triggered and the BLE event is handled on our device. But this interrupt is never triggered when the data packet is larger than 20 bytes.

Any idea or advice on how to debug this is very appreciated!

Best regards,

Gamli

[gamli]

And to add to this, I did monitor the communication in Wireshark using a BLE sniffer with an nRF52840 dongle and did see that the packets were sent over the air, both a 20 bytes packet and when I increased the size to 22 bytes and larger. But as mentioned earlier, no interrupt was registered with the larger packets.