Re: [avrdude-dev] Butterfly proposal: Exit upgrade function

[Martin Thomas]

> On Thursday 05 February 2004 02:12, Martin Thomas wrote:
> 
> > /*
> >  Usual scenario: Users uploader the hex-file, wait for avrdude  to
> > complete the transfer and push the Butterfly's joystick "up" (=jump
> > to 0x0000) to see if the application works.
> >
> >  If the Butterfly does not receive an "E" after flash upload  it
> > stays in "910 mode" and waits for other commands from UART.  The
> > loop where the joystick position gets read is independant from the
> > 910 command interpreter  loop. Because of BOOTRST the BF jumps to
> > the Bootloader. In the preloaded application the selection
> > Options/Jump to Bootloader issues as WD reset. In the Bootloader
> > the BF goes to sleep, the joystick is connected to ExtINT pins. If
> > the joystick is pushed up: jmp 0x0000, if joystick is pressed the
> > BF tries to sync with the flash-software (AVRPROG or
> > avrdude/butterfly via RS232. After a handshake it breaks from the
> > joystick-loop and enters the "infinite" command- parser-loop. Exit
> > from this loop is via WD-reset on "E" send via RS232 */
> 
> Do I get this right?
> - If you don't send the "E" you can only enter the program by powering 
> down and then pressing a button.

Yes, powering down or "hardware reset"

> - If you send the "E" you still have to press the button (it is a 
> joystick, AFAIK) to start the program?

Yes, "E" does a WD reset, which means "restart bootloader", Exit
from Bootloader is joystick up (wake up from sleep in the preinstalled
application is the same so the user does not notice the difference)

> - If you send the "E" you have to press another button to be able to 
> connect to the bootloader once again?

Yes, if there was no js-"up" after "E" the bootloader is active and
awaits handshake only if "enter" is pressed.

> I don't have a butterfly, but your text and the bootloader source code 
> look like this is how it works ;-(

It's a little strange but the firmware is "tuned" to save battery power.

I've ported the bl to avr-gcc but it doesn't make sense to adopt
avrdude/butterfly.c to another bootloader than the preinstalled one.

Martin