Re: [avr-gcc-list] Bootloader question

[Scott Morken]

Hi,
I have tried not disabling the watchdog, and it does go to the 
bootloader. But when I do this the bootloader rapidly resets over and 
over and does not make it into its command loop, even if I disable the 
wdt early in the bootloader code.

Scott

Bernard Fouché wrote:
> Scott Morken wrote:
> > Hi
> >
> > I have an application that jumps to the bootloader using this 
> > function (it's a slightly modified avr109 bootloader made by atmel):
> > void (*funcptr)( void ) = (void *)0x3800; // Set up function pointer 
> > to the bootloader start.
> >
> > I call it when a command is sent over the serial port, making this 
> > code run:
> > UART_SendByte('B');
> > wdt_disable();//disable watchdog
> > cli();//disable all interrupts
> > for(counter = 0; counter<20000; counter ++)
> > {
> >    asm("NOP");
> > }
> >                       funcptr();//goto bootloader
> You call your bootloader like a function, so the MCU is not 
> re-initialized: pending interrupts may be fired if ever the booloader 
> call sei(), the stack may be near its end, etc. Why not do your timing 
> loop, but with the watchdog still enabled? That would make the MCU 
> restarts and go to the bootloader if the fuses are set correctly (I'm 
> used to 64/128/1280 pieces, I dunno about the 168 bootloading 
> requirements)
>
>  Bernard