fix iwdg example and add code to disable iwdg in halt

[PocketPi]

fix iwdg example and add code to disable iwdg in halt

When using the example to enable and use the iwdg i found that when i had my cpu enter halt the watchdog kept running and timed out even though i had enabled that the cpu should stop in halt mode.

I found looking at some legacy code that setting KR to 0xAA and not 0xCC fixed the problem.

Maybe the 0xAA is a copy paste error?

I have also added a function to disable watchdog in halt in the option bytes

[gicking]

Thanks for pointing this out to me!

Now I'm trying to understand and test your changes. Which specific STM8 variant are you using?

[gicking]

Intermediate update:

I have played around with a STM8S Discovery board to check your observation and proposed changes. Here is my current status:

1. my code is pretty messy :-( However, I don't actively develop these device headers anymore, as all STM8 are now "not recommended for new designs". So much for the protocol... ;-)

2. I confirm that with the original example IWDG is running in HALT mode with AWU -> IWDG triggers a reset in HALT mode :-(

3. KR=0xCC starts IWDG via software (see RM0016 v14, section 14.3.1). Writing KR=0xAA only refreshes the counter, but does not start IWDG. I confirmed this experimentally

4. So far I haven't found a way to deactivate IWDG in HALT mode (with AWU) -> need to ask in STM user forum

5. IMHO your proposed function disable_iwdg_in_halt() should work for (at least most) STM8L/AL. However:

   • STM8S/AF apparently lack the respective option bit (see datasheet)
   • for STM8S/AF you also need to store the inverted NOPT, else the µC remains in a reset cycle
   • you should only modify the option bits you need, not write the whole byte. Else you risk overwriting the WWDG options

[gicking]

Update:

• STM8S/AF doesn't support stopping IWDG in HALT mode, see here --> re-configure IWDG for 1s max. timeout, wake up via AWU periodically, service IWDG and re-enter HALT with AWU

• I will check your proposal for STM8L/AL using a STM8L Discovery Board. Stay tuned...