Volumio 1.5 won't boot from SD on BBB Rev. C


I’m struggling to boot Volumio 1.5 from a SD card on BBB Rev. C.

I have succeeded only once. I looked at the Volumio UI. All other trials failed and always Ubuntu Linux is booted from emmc. I have flashed the SD card two times.

The reason is, when I powered on the board with pressing the S2 button, boot starts from the SD card and the boot loads Ubuntu Linux from emmc.

To confirm this scenario, I renamed MLO to MLO-backup on emmc. Ubuntu Linux is still started and I can log in with ssh!!

I think uEnv.txt in the boot partition of Volumio 1.5 in the SD card is wrong.

Here is the uEnv.txt. I think the ext4load in the if statement returns False. Why? Why? Why?

loadfdt=ext4load mmc ${mmcdev}:2 ${fdtaddr} /boot/dtbs/${fdtfile}
loaduimage=mw.l 4804c134 fe1fffff;
if ext4load mmc 0:2 ${loadaddr} /boot/zImage;
mw.l 4804c194 01200000;
echo Booting from external microSD…;
setenv mmcdev 0;
setenv mmcdev 1;
if test $mmc0 = 1;
setenv mmcroot /dev/mmcblk1p2 rw;
ext4load mmc 1:2 ${loadaddr} /boot/zImage && mw.l 4804c194 00c00000;
echo Booting from internal eMMC…;

I have read the following threads. But they are not essential solution.