"Length of data to send exceeds MTU" message on nrfConnect

[yayembedded]

When I do a DFU on my device (nrf52832 with Zephyr) using nrfConnect, the update is successful, but I get a message in the log stating "Length of data to send exceeds MTU".

I tried Googling about this but found nothing.  Is this something I should be concerned about for production?

[Simonr]

Hi

Sorry, but this wasn't clear from the initial post, are you using nRFConnect for Desktop, nRFConnect for Android, or iOS?

Best regards,

Simon

[yayembedded]

ios

[Simonr]

Hi Christopher

Thank you, I discussed this with our nRFConnec for iOS developer, and this disconnect is normal. The DFU process waits for the device to restart to confirm a successful DFU. The line "State changed from test to reset" in the log tells you that it is now going to reset the device.

So there is nothing to be worried about in production.

Best regards,

Simon

[yayembedded]

Hi Simon.  Yes I know about the confirmation procedure.  My concern is about the message that says, “Length of data to send exceeds MTU”.  Sounds like there is something I should change.

Here are my prj.conf settings:

# Allow for large Bluetooth data packets.
CONFIG_BT_L2CAP_TX_MTU=252
CONFIG_BT_L2CAP_RX_MTU=252
CONFIG_BT_RX_BUF_LEN=260

I copied them from the ncs\v1.4.1\zephyr\samples\subsys\mgmt\mcumgr\smp_svr sample project.

[Simonr]

This should not be an issue, this only means that the iOS DFU library will send the data in more than one transmission, and will not cause any problems for you.

Best regards,

Simon