eMMC Flash Storage and microSD Card Boot on BeagleBone

Trent,

When I read the beaglebone black documentation, it was my understanding that the boot button had to be pressed every time you wanted to use the SD card to be the boot device.  That has not been my experience though.  I have been booting from the SD card because it has the latest operating system.  (I haven't bothered burning it to the eMMC chip).  I had to press the boot button the first time I wanted to use the SD card.  After that, it always booted from the SD card, without me pressing the boot button.  It seems like it's a latching button.

I was thinking I should try removing the SD card, and seeing if that stopped the latching.  But it's on my long list of mysteries to solve.

Allen

Hi Allen,

It seems like the eMMC boots without the sd to an outdated iot image that was previously installed. I origally flashed the eMMC on both my Black Wireless and Blue with the beagleboard debian iot image. When booting from the microSD, I've always held the sd boot button. I didn't know if it was possible to boot from sd without holding the button down.

Trent

In case anyone really wanted to know the answer, I ran some tests today.  Yes, the Boot button (which lets you boot from the SD card instead of the on-board eMMC memory) is "latching".  (All this was done with $sudo shutdown now) More latching that I expected:

-boot with no SD card                                                   -boots from eMMC (of course)

-SD card, hold Boot button briefly while power it up     -boots from SD card

-power down, then up,don't hold Boot button               -boots from SD card  (so it's latching)

Then I immediately tried this:

-then remove SD card, power on                      -boots from eMMC (of course)

-power down, then up, don't hold Boot button  -still latched from previous, boots from SD card

much to my surprise, it latches even after having a reboot with the SD card removed.

As an aside, all this rebooting showed me that the eMMC  memory is much faster than the SD card access.  I'm using the clever USB/ethernet connection to 192.168.7.2, and Cloud9 IDE and other apache pages display much faster when using the eMMC.

Hi Allen,

Thank you for for testing this. The boot procedure was a bit confusing at first but you have clarified how the BeagleBone is handling the the microSD.

So I've made the error of holding the boot button every time I wanted to run the image from the microSD.

I wouldn't call it an error.  What you were doing is how I understood the BBB instructions.  Maybe I'll read thru the SRM again to see the exact wording.

I wouldn't call it an error.  What you were doing is how I understood the BBB instructions.  Maybe I'll read thru the SRM again to see the exact wording.