Robert,

My BBB absolutely must default to booting from the uSD. I know I 
could short the boot switch, or move pull-up/down resistors, or create a 
hardware switch gated from reset, but I don't want to lose hardware 
compatibility with other BBB boards, or give up the option of manually 
booting from eMMC occasionally. The code you suggest here sounds perfect - 
but I'm not positive what to do with it. From the formatting of the text, I 
suspect it is intended to be compiled into a new u-boot.img and MLO image, 
but I'm not sure how to do that. 

Before I spend hours learning how, is there a chance I could just insert 
the basic ideas into my uEnv.txt as "mmcboot=mmc dev 0; if mmc rescan ; 
then ..."? It does look like uEnv.txt is read before the mmcboot command 
runs...  

If so, does it have to be run together into a single ';' separated line, or 
can I leave the '\' line continuations in to make it more readable? 

I suspect uEnv.txt would not want the double-quotes? Or Windows <CRLF> line 
endings...  

If that is totally hopeless, can you suggest a tutorial on building a new 
u-boot.img and MLO with this code? 

Thank you for any clues,

Loren

On Thursday, January 2, 2014 2:16:47 PM UTC-8, RobertCNelson wrote:
>
> I have mine setup as the following.. 
>
> +        "mmc dev 0; if mmc rescan ; then " \ 
> +                "gpio set 54; " \ 
> +                "setenv mmcdev 0; " \ 
> +                "echo SD/MMC found on device ${mmcdev}; " \ 
> +                "if run loadbootenv; then " \ 
> +                        "run importbootenv; " \ 
> +                "fi; " \ 
> +                "gpio set 55; " \ 
> +                "echo Checking if uenvcmd is set ...;" \ 
> +                "if test -n $uenvcmd; then " \ 
> +                        "gpio set 56; " \ 
> +                        "echo Running uenvcmd ...; " \ 
> +                        "run uenvcmd;" \ 
> +                "fi; " \ 
> +                "echo; echo uenvcmd was not defined in uEnv.txt ...; 
> echo trying eMMC (BeagleBone Black) ...; echo;" \ 
> +        "fi;" \ 
> +        "mmc dev 1; if mmc rescan ; then " \ 
> +                "gpio set 54; " \ 
> +                "setenv mmcdev 1; " \ 
> +                "echo SD/MMC found on device ${mmcdev}; " \ 
> +                "if run loadbootenv; then " \ 
> +                        "run importbootenv; " \ 
> +                "fi; " \ 
> +                "gpio set 55; " \ 
> +                "echo Checking if uenvcmd is set ...;" \ 
> +                "if test -n $uenvcmd; then " \ 
> +                        "gpio set 56; " \ 
> +                        "echo Running uenvcmd ...; " \ 
> +                        "run uenvcmd;" \ 
> +                "fi; " \ 
> +                "echo; echo uenvcmd was not defined in uEnv.txt ...; 
> echo halting ...; echo;" \ 
> +        "fi;" \ 
>
>

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