The max amount of time can be spent in WDT interrupt

RE: The max amount of time can be spent in WDT interrupt

Andy — Tue, 19 Jun 2018 11:48:13 GMT

Oh, so then the RESETREAS register does work

RE: The max amount of time can be spent in WDT interrupt

Einar Thorsrud — Tue, 19 Jun 2018 11:15:41 GMT

Referring to the table I linked to in my previous post, you can see the 'x' in the intersection between the "Watchdog reset" and "Retained registers". This indicates that the retained registers are reset by a watchdog reset. However, what this really means is that the content is not guaranteed. In practice it should work most of the time (perhaps always), as you write.

RE: The max amount of time can be spent in WDT interrupt

Andy — Tue, 19 Jun 2018 11:04:56 GMT

I don't see anything there that says that it's not guaranteed. At least it has been working consistently for me ever since I implemented it. The RESETREAS is not supported, that's what I can see.

RE: The max amount of time can be spent in WDT interrupt

Einar Thorsrud — Tue, 19 Jun 2018 11:00:25 GMT

That is true. But you should be aware that the content of GPREGRET is not guaranteed after a watchdog reset (see Reset behavior table). So a CRC or similar to validate it is recommended.

RE: The max amount of time can be spent in WDT interrupt

Andy — Tue, 19 Jun 2018 10:48:09 GMT

You don't need to write to flash. I write a code to the GPREGRET in order to stay in bootloader after a watchdog reset. You could do the same for whatever purpose you need.

RE: The max amount of time can be spent in WDT interrupt

Einar Thorsrud — Tue, 19 Jun 2018 10:44:09 GMT

Hi,

You have two 32 kHz clock cycles before the reset occurs. As you write, this means that there is no time for writing to flash, and it is not configurable.

An alternative is that you could write data to a reserved RAM region instead, and check that region after every reset. The content of the RAM is not guaranteed through a watchdog reset, so you should write a CRC together with the data so that you can verify that the data is intact when you read it back after the reset.