better documentation for nrfutil serial option

RE: better documentation for nrfutil serial option

tesc — Tue, 16 Mar 2021 09:57:35 GMT

Hi,

I guess there could be some pointers to the SDK documentation, if anything.

Reliability of serial communication: If the transmitting end sends data faster than the receiving end can handle it, then some data will get discarded. With hardware flow control, the receiver signals when it is ready for more data, ensuring that this does not happen. One reason for the receiver not being ready, in the context of DFU, is that flash writing can be a bottleneck, leading to full RX buffers.

Regards,
Terje

RE: better documentation for nrfutil serial option

AMarch — Mon, 15 Mar 2021 14:28:12 GMT

That explains it but I do believe it should be documented at the level of the nrfutil.

I suppose a follow up question would be, "why would serial without flow control be less reliable?"

RE: better documentation for nrfutil serial option

tesc — Mon, 15 Mar 2021 13:16:56 GMT

Hi,

The -prn option (long form --packet-receipt-notification) sets the packet receipt notification to use for the DFU process.

This parameter is documented in the SDK documentation, both for the specific use case of serial transport, and in general for the DFU protocol.

The short explanation:
PRN is disabled if set to 0. Otherwise, for every PRN number of packets transferred, the DFU target sends back a CRC for the controller to check that the firmware (thus far) is correctly transferred. Use it for unreliable transport layers (such as BLE or serial without flow control.) The higher the number, the more packets sent between each check. The lower the number, the more overhead due to checking.

Regards,
Terje