Is there a packet size limitation for the bootloader?

RE: Is there a packet size limitation for the bootloader?

Anne van Rossum — Fri, 16 Jan 2015 14:25:44 GMT

Okay, although I prefer it to be on a public place, so others can see it as well. :-)

RE: Is there a packet size limitation for the bootloader?

Petter Myhre — Fri, 16 Jan 2015 14:10:23 GMT

I'm just trying to say that long writes will not improve the throughput. We want to help you figuring out what is causing the fault, therefore I asked you to separate case/question for it. Then you can include the necessary details of what changes you have done to the bootloader and what your setup is on the central side.

RE: Is there a packet size limitation for the bootloader?

Anne van Rossum — Fri, 16 Jan 2015 13:32:36 GMT

There is "something" in the configuration of the DFU uploader in the Nordic app that makes the Nordic bootloader fail. I see that the Nordic bootloader segfaults if I use long writes in a python script. I think it is size-related. You say it is not. It is not my code. Please, see this just as bug report. I'm not here to start a discussion.

RE: Is there a packet size limitation for the bootloader?

Petter Myhre — Fri, 16 Jan 2015 12:49:47 GMT

Why do you ask about size limitations if you don't care about them? I think this issue us better suited for the MyPage support portal, please consider adding a case there.

RE: Is there a packet size limitation for the bootloader?

Anne van Rossum — Fri, 16 Jan 2015 12:19:29 GMT

The DFU upload functionality embedded in the Android smartphone app fails as well. I don't care about size limitations, but I do care about my program segfaulting due to configuration options (I assumed them to be size-related) on the smartphone / laptop side.

Note that this is just the default bootloader with only a few adaptations: github.com/.../nrf51-dfu-bootloader-for-gcc-compiler, fork from github.com/.../nrf51-dfu-bootloader-for-gcc-compiler. It is not that I changed a lot of stuff. So, perhaps it's nice of someone from Nordic would take a second look to check if everything is still working okay. :-)

RE: Is there a packet size limitation for the bootloader?

Petter Myhre — Fri, 16 Jan 2015 12:13:57 GMT

With the current SoftDevice the payload is limited to 20 bytes.

Long writes will not change that, please see this.

The time it takes to do DFU is affected by other factors than the payload size, please see this for more information.

One thing that should quicken the procedure is to increase the number of packets between each packet receipt notification. From the Master Control Panel DFU script:

# NOTE:  If packet receipt notification is enabled, a packet receipt
#        notification will be received for each 'num_of_packets_between_notif'
#        number of packets.
#
# Configuration tip: Increase this to get lesser notifications from the DFU
# Target about packet receipts. Make it 0 to disable the packet receipt
# notification
num_of_packets_between_notif = 10

This can also be changed in the DFU Options in the nRF Master Control Panel for Android.

RE: Is there a packet size limitation for the bootloader?

Anne van Rossum — Wed, 07 Jan 2015 18:10:41 GMT

I would be surprised if that would be actually the reason. Sending the individual packets is actually fine. There is only a problem at the very end of receiving the entire payload. I will check anything w.r.t. long writes within the bootloader software though.

RE: Is there a packet size limitation for the bootloader?

John — Wed, 07 Jan 2015 14:44:01 GMT

Writing to a standard characteristic is limited to 20 bytes. The MTU of the packet is 23 bytes and there are 3 bytes of overhead imposed by the protocol. BLE does provide for writing long characteristics and I believe the later versions of the Nordic stack supports them. Here is a rather old question on the topic that may be useful:

Old question

So you may want to look into adding the use of long writes to your DFU