Root Filesystems

There are a couple of options to assembling a development environment (compile chain and root filesystem) for the MitySOM-335x platform.

MDK Release November 2015 Yocto

The root filesystem tarball is in the deploy directory of the the MDK release
The default install location of the MDK installer is /opt/criticallink, if this differs change your path accordingly

To copy this onto an SD card that is already partitioned

$ cd /opt/criticallink/mitysom-335x_20151118/deploy/
$ sudo rm -r /media/rootfs/*
$ sudo tar -xjvf mitysom-335x-devkit-mitysom-335x.tar.bz2 -C /media/rootfs/

The MDK release can also be built yourself and customized, see the following wiki page.
Building the Root Filesystem with Yocto


Critical Link has partnered with Timesys in order to provide commercial support for the MitySOM-335x. Timesys has downloadable images, please see their AM335X dev page for details.

TI AM335x EVM (used by MitySOM-335x DevKit)

Note: This base filesystem is quite old and the opkg repos have expired. The timesys filesystem is the recommend.

The sample linux root file system for the MitySOM-335X is included in the AM335X_devkit on the SD-Card as well as on the Virtual Machine appliance linux build image. Unix Tar archives of our base file system are provided on this site (, see rootfs.tar.gz. The linux root file system included is essentially a copy of the root filesystem included with TI's am335x EVM (version 5.03.02) with minor modifications to support the MityOSM-335x (specifically, the kernel has been updated to support the MitySOM-335X development kit and some of the demos relying on the EVM hardware configuration have been disabled). TI's root filesystems are developed on their Arago-Project page, which is a custom distribution build on top of the Open Embedded build system. You can reproduce their base images by following the instructions on the Arago-Project wiki.

Much of the details of the AM335x EVM and support files from TI have been covered on the TI wiki

Build your own environment using Open Embedded

Critical Link has been able to compile the Qt 4 embedded toolchain and Angstrom Distribution basic console and X11 file system images using the Open Embedded build system with a local kernel port and a simple layer addition. We will include copies of the base image, a full image (includes qt4 embedded support), and a full X11 / Gnome image as well as cross tool SDK tarballs for bit 32 bit and 64 bit machines on the Files Section of this wiki.

A short description of what was done to create the filesystems and SDK is included in the Installing Open Embedded page.

Critical Link does not officially support the use of Open Embedded / Angstrom builds.

Booting the Root Filesystem

The Critical Link MitySOM-335x Development Kit is initially configured to boot from an SD Card. Other boot options require further configuration of U-boot and the kernel. Please contact Critical Link for guidance regarding your specific application.

Boot Root Filesystem from Nand

UBIFS Nand Boot

TFTP Kernel Boot with an NFS Root Filesystem

The kernel and root filesytem can be provided by a networked server. Here is a sample configuration for boot a kernel via TFTP that uses an NFS root filesystem. You may need to make significant changes to this example to make it work for your specific application.

Server configuration

First, create a sample filesystem on the server. You can start with the base filesystem available through Timesys.

$ pwd
$ mkdir nfsroot
$ cd nfsroot
$ sudo tar zxvf filesystem-base.tgz 

NOTE: Please remember to execute the tar command as the root user.

Then, append this line to your /etc/exports file:

/home/bob/nfsroot *(rw,nohide,insecure,no_subtree_check,async,no_root_squash)

and restart your nfs server. You can run
$ sudo exportfs 
to verify the nfsroot directory is there.

Finally, move the kernel image from the boot directory to your TFTP server directory:

$ pwd
$ cp nfsroot/boot/uImage /tftpdirectory

Consult your GNU/Linux distribution documentation for TFTP server configuration.

MitySOM 335x Development Kit Configuration

If your server is properly configured, here is a valid U-boot configuration for booting via the network (kernel via TFTP and root filesystem via NFS). Note: You will need to review and modify the network and filepath settings for your specific configuration.

U-boot> setenv autoload no; dhcp; setenv serverip;setenv bootfile uImage; tftpboot
U-boot> setenv bootargs "console=ttyO0,115200n8 root=/dev/nfs nfsroot=${serverip}:/home/bob/nfsroot,nolock rw ip=dhcp" 
U-boot> bootm 0x82000000

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