Timeouts on Arduino Nano Every are divided by 4

[Plontine]

On Nano Every the actual timeouts come like this: 8S, 4S, 1S make 250 ms. 2S makes 500 ms. 500MS makes 125 ms. 250MS makes 68 ms. Lower values not tested.
Just a note: watchdog.tripped() does work fine.

[meszibalu]

The WDTO_* constants are not good on every. These constants must be used:

/* Period select */
typedef enum WDT_PERIOD_enum
{
    WDT_PERIOD_OFF_gc = (0x00<<0),  /* Off */
    WDT_PERIOD_8CLK_gc = (0x01<<0),  /* 8 cycles (8ms) */
    WDT_PERIOD_16CLK_gc = (0x02<<0),  /* 16 cycles (16ms) */
    WDT_PERIOD_32CLK_gc = (0x03<<0),  /* 32 cycles (32ms) */
    WDT_PERIOD_64CLK_gc = (0x04<<0),  /* 64 cycles (64ms) */
    WDT_PERIOD_128CLK_gc = (0x05<<0),  /* 128 cycles (0.128s) */
    WDT_PERIOD_256CLK_gc = (0x06<<0),  /* 256 cycles (0.256s) */
    WDT_PERIOD_512CLK_gc = (0x07<<0),  /* 512 cycles (0.512s) */
    WDT_PERIOD_1KCLK_gc = (0x08<<0),  /* 1K cycles (1.0s) */
    WDT_PERIOD_2KCLK_gc = (0x09<<0),  /* 2K cycles (2.0s) */
    WDT_PERIOD_4KCLK_gc = (0x0A<<0),  /* 4K cycles (4.1s) */
    WDT_PERIOD_8KCLK_gc = (0x0B<<0),  /* 8K cycles (8.2s) */
} WDT_PERIOD_t;

[peterpolidoro]

These constants are for which boards? Do you know the macro that checks for these types of boards? (e.g. #if defined(AVR_ATmega32U4) )

[meszibalu]

These constants are for Atmega 4809 controllers (specification page 190). These controllers are used on Arduino Nano Every boards.

I use to use this macro:

#if defined(ARDUINO_AVR_NANO_EVERY)

I found these constants in packages/arduino/tools/avr-gcc/7.3.0-atmel3.6.1-arduino7/avr/include/avr/iom4809.h. It is included from packages/arduino/tools/avr-gcc/7.3.0-atmel3.6.1-arduino7/avr/include/avr/io.h:

#elif defined (__AVR_ATmega4809__)
#  include <avr/iom4809.h>

If you want to test it, I compiled the code with this command:

arduino-cli compile --clean --warnings more -b arduino:megaavr:nona4809:mode=off sketch.ino