I have prepared a uboot.img, MLO, uImage, am335x-boneblack.dtb, uEnv.txt Files for Beaglebone black board by following from this site
I also created boot and rfs partition on sd card and copied MLO then uboot.img and then other files. I booted by holding switch S2 and got this log
U-Boot SPL 2016.07-00224-g62a3b7d (Jul 16 2016 - 23:35:47)
Trying to boot from MMC1
MMC partition switch failed
*** Warning - MMC partition switch failed, using default environment
U-Boot 2016.07-00224-g62a3b7d (Jul 16 2016 - 23:35:47 +0530)
DRAM: 512 MiB
MMC: OMAP SD/MMC: 0, OMAP SD/MMC: 1
*** Warning - bad CRC, using default environment
Net: <ethaddr> not set. Validating first E-fuse MAC
Press SPACE to abort autoboot in 2 seconds
switch to partitions #0, OK
mmc0 is current device
SD/MMC found on device 0
** Unable to read file boot.scr **
351 bytes read in 4 ms (85 KiB/s)
Loaded env from uEnv.txt
Importing environment from mmc0 ...
Running uenvcmd ...
Booting from Network ...
7677504 bytes read in 690 ms (10.6 MiB/s)
61606 bytes read in 13 ms (4.5 MiB/s)
## Booting kernel from Legacy Image at 82000000 ...
Image Name: Linux-4.4.15+
Created: 2016-07-16 18:30:19 UTC
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 7677440 Bytes = 7.3 MiB
Load Address: 80008000
Entry Point: 80008000
Verifying Checksum ... OK
## Flattened Device Tree blob at 88000000
Booting using the fdt blob at 0x88000000
Loading Kernel Image ... OK
Loading Device Tree to 8ffed000, end 8ffff0a5 ... OK
Starting kernel ...
It just cannot boot kernel I don't know why?