Slow DFU using nrfutil

[Michal L.]

Hi,

I am preparing Windows desktop application which will use nrfutil for DFU of the products (containing secure dfu bootloader). I tested nrfutil v6.1.0, v6.0.1 and even very old v3.2.0 and in all cases update takes very long time - 100 kB firmware is updated in more than 10 minutes. If I do it via nRF Connect app on iPhone or Android, it tooks literally tens of seconds. I tried also nRF Connect for Windows and the situation is the same, also about 10 minutes. I tried it on nRF52832 DK, nRF52833 DK and nRF52840 DK, results are the same.

I tried to compile nrfutil from the sources with decreased conn interval in BLEGapConnParams (changed it to 7.5 both min and max) but it also didn't solve the problem.

Any ideas?

[Vidar Berg]

Hi,

DFU with pc-nrfutil is known to be quite slow, but nRF connect on windows should be on par with nRF connect on Android and iOS, so that's more suprising. Which SDK is the bootloader on the target based on?

Thanks,

Vidar

[Michal L.]

Today I tried to downgrade to pc-ble-driver-py v0.14.1 and pc-nrfutil v6.0.1 and compile executable nrfutil. Behaviour is still the same, update still lasts 10 minutes. 

Florian Zierer wrote here that in his case in v6.0.1 problem was solved, so I don't know, what could be wrong now..

[Michal L.]

Thank you for the information.

[Michal L.]

Hello,

do you have any updates? 

[Vidar Berg]

Hello,

Sorry for the delayed response. I have done some investigations on my own now, and I am starting to suspect it may have something to do with the USB stack on Windows. The reason for this is that I'm seeing much higher throughput when I test DFU on my Linux PC with the exact same script. Also, modifying the connection parameters in the script did not  have any noticeable impact on the transfer speed for windows ( implying it's not bottlnecked by the connection configuration). 

Multiple DFU payload packets per connection event on Linux

And less than one paylod packet per connection interval on Windows

Do you have a PC running linux natively that you can try this on?

[Michal L.]

Hello,

I finally had time to test it on Linux PC (actually Linux running in VirtualBox). And results are really much better than in Windows - whole update lasts ca 45 sec. in Linux (same update package lasts 11 min. in Windows).

What exactly is bottleneck in Windows? I thought it is just matter of DK running Connectivity firmware and that nrfutil just sends data to the kit via UART. Or am I wrong?

[Vidar Berg]

Hello,

OK, it's good to know that it performs better on VMs as well. Thanks for confirming that. I thought maybe it had to be run natively.

Michal L. said:

What exactly is bottleneck in Windows? I thought it is just matter of DK running Connectivity firmware and that nrfutil just sends data to the kit via UART. Or am I wrong?

 You are not wrong. I believe the problem with Windows is that the USB commands and responses are sent and received too slow. The required USB bandwidth is not much, but latency is more critical as the interface protocol requires transmissions and reception of many small packets.