Cant Boot when Cape is connected

Im trying to use a cape developed by my team that has a lot of sensors and an FPGA, but as part of the connections between FPGA, sensors and BBB processor they used the MMC PINS, the ones that are destined for the eMMC. The cape works fine, but if I plug it in then the BBB does not boot. If I plug the cape after the BBB has booted, then everything is alright.

I tried changing to boot from an SD card and disabling the eMMC, but I cant boot anyways. I know the eMMC is disabled because I got this output :

root@beaglebone:~# cat /sys/devices/bone_capemgr.*/slots
0: 54:PF—
1: 55:PF—
2: 56:PF—
3: 57:PF—
4: ff:P-O-- Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G
5: ff:P-O-- Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI
6: ff:P-O-- Bone-Black-HDMIN,00A0,Texas Instrument,BB-BONELT-HDMIN
7: ff:P-O-L Override Board Name,00A0,Override Manuf,BB-I2C1


Any idea of what I am doing wrong? Or what else could I do to be able to boot?

Any help will be appreciated.


By default, you cannot drive or significantly load the eMMC lines until
the board has booted. The system will read the initial MLO boot loader
and uBoot off of the eMMC, then boot from the uSD card if one is
present. Loading or driving the eMMC lines interferes with this process.

Your choices are to force a direct boot off of the uSD using the boot
lines (conditioned with the system reset line) or to not drive the eMMC
signals until the system has come up and indicated to your hardware that
it is now safe to do so.

This is covered in the BBB SRM, see sections 8.1.1 and 8.1.2.

Thanks Charls,

That was the right answer at the end, to not drive the eMMC signals until the system had booted. Thanks for the help.