problem with the MCUSR

[jar10623]

on a arduino nano328p this code worked fine:

before setup:
uint8_t my_mcusr=MCUSR;
in loop:
myGLCD.print("my_mcusr= ", LEFT, LINE7);
sprintf(r_str, ""%03d"", my_mcusr);
myGLCD.print(r_str, RIGHT, LINE7);

connected with PC in the Arduino IDE
on nano328p output MCUSR dec 6
on mighty1284p output MCUSR dec 0

on power supply with powerON
on nano328p output MCUSR dec 5
on mighty1284p output MCUSR dec 0

on power supply with push resetSWITCH
on nano328p output MCUSR dec 7
on mighty1284p output MCUSR dec 0

has anyone an idea?

[baldowl]

It should be the bootloader: assuming you're using the old optiboot version bundled with this code, it resets MCUSR before starting your code.

[jar10623]

is there any correction?

maybe a new bootloader.hex for 1M Baud Optiboot and 16MHz F_CPU?

[baldowl]

I think it's better if you ask in the more active fork: https://github.com/JChristensen/mighty-1284p

Or you can compile and replace the bootloader: https://github.com/Optiboot/optiboot

[jar10623]

thanks, soory i don't can compile it by myself and the Link only gives
a HEX file to

atmega1284o.name=[Optiboot] ATmega1284p
atmega1284o.upload.speed=115200

and not to 1M upload?

i use Arduino 105

[baldowl]

Ok, then have a look at https://gist.github.com/baldowl/e6593d53f2454159571b

I compiled the Optiboot's current master using the tool chain bundled in Arduino's IDE version 1.6.6, but, mind you, it doesn't matter so you don't have to upgrade IDE or whatnot: just burn the bootloader.

Note that MCUSR is still reset but its value is saved in R2 so it's available for your application.