RE: antfs.c sample code bug during interrupted download

Kenneth — Thu, 01 Oct 2020 07:36:27 GMT

Hello,

The team have found out why ANT FS Client failed to resume the file downloading process after temporary interruption.

It turns out that the CRC save point is updated systematically with every data packet that is sent from the Client to the Host during the file transfer. ANT protocol cannot detect disconnect straight away, so it keeps on sending data packets and updating CRC save points. Later on, if the ANT PC tool recognizes interrupted transmission, it tries resuming the downloading process by setting a dedicated bit in the download command. It also indicates the file offset from which the file transfer should continue. However, the offset of the CRC save point, which was calculated by the ANT FS Client, is greater than the file offset requested by the Host. The Client rejects the whole downloading operation because it cannot verify the CRC of data packets that were received on the Host end. One of the possible solutions to this issue is to store multiple CRC save points during the downloading process and roll back to the closest one when the file transfer is interrupted. Currently, there is only one CRC save point, and that's why this becomes a problem.

The team have included a modified version of antfs.c which handles the temporary transfer interrupts. However, this version skips the CRC verification step after the transmission is interrupted. As a test, they tried downloading the same file two times: once without any transfer interruptions and the second with at least one such interrupt. It turned out that both versions of the file were binary equal. This experiment demonstrates that the file transfer with resuming functionality is feasible.

We hope that the modifications is a good starting point to improve ANT FS implementation further. Unfortunately the team don't have time to see this further as of now.

Best regards,
Kenneth

devzone.nordicsemi.com/.../7587.antfs.c

RE: antfs.c sample code bug during interrupted download

Kenneth — Wed, 30 Sep 2020 07:35:44 GMT

Looks like the person looking into the case is out of office this week. So likely no update until then, sorry for the delay.

Best regards,
Kenneth

RE: antfs.c sample code bug during interrupted download

Kenneth — Mon, 21 Sep 2020 11:23:47 GMT

Hi,

Sorry for time this is taking, they are looking into it.

Best regards,
Kenneth

RE: antfs.c sample code bug during interrupted download

rschmitz — Fri, 18 Sep 2020 16:36:31 GMT

Hello Kenneth, Is there any update on this bug? It is holding up our software release now. Thanks!

RE: antfs.c sample code bug during interrupted download

Kenneth — Wed, 26 Aug 2020 11:32:12 GMT

I have forwarded your case to the software developers. We will try to provide an update soon.

Kenneth