GATT Timeout on writing to buttonless dfu characteristic

[fhfs]

Hello Devzone,

We update our peripheral device(nrf52) with our gateway(nrf52840, central) using the DFU protocol. We have this working and the DFU update is successful when the device actually restarts to the bootloader.

However, when we start the DFU process by writing the instruction to restart to the bootloader, to the buttonless dfu characteristic. We sometimes get a gatt timeout (BLE_GATTC_EVT_TIMEOUT). We are subscribed to the buttonless dfu characteristic and we are using SDK 17.0.2.

Do you have any idea why we are getting this gatt timeout?

I reviewed the DFU logs from the nRF Connect app, and I've noticed a delay after the service discovery and subscribing to notifications. Do we need to add a delay there?

[Simonr]

Hi

Sorry that I haven't gotten back to you until now. Have you still not been able to get a sniffer trace of the timeout occurring? If the TIMEOUT only occurs on one of the security modes, it seems like one of the devices have not implemented support for Security level 4: LESC MITM protected encrypted link using a 128-bit strength encryption key required.

How does your devices implement these security modes?

Best regards,

Simon

[fhfs]

How does your devices implement these security modes?

We use nrf52 devices on either side of the connection. The connection works fine, the problem only occurs when we try to update the devices.

Sniffing using the SC LTK works for the most part. I've tested the devices where we got the GATT Timeouts, but I cant seem to recreate the problem. Leaving this issue resolved until it reoccurs.