CM-T43: Yocto Linux: Manual Installation

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Introduction

This article provides an introduction on how to install the Yocto example root filesystem image on the CompuLab CM-T43 System-on-Module / Computer-on-Module internal storage.

Preparation steps

  • Obtain a PC workstation with a serial communication port.
  • For networked installation you need to install a TFTP server on the host PC. For Windows machines we recommend TFTPD32 included in the Yocto Linux package for CM-T43 (link below).
  • Download the Yocto Linux package for CM-T43 from CompuLab website. Unzip the package to a directory on your host workstation.
  • All image files mentioned below can be found in the package root directory under install directory.
  • Connect the host PC to the SB-SOM-T43 base-board (connector P8) via the serial cable supplied with the evaluation kit.
  • Start terminal emulation software on your PC with the following serial port settings:
Baud Rate Data Bits Stop Bits Parity Flow Control
115200 8 1 none none
  • Turn on the CM-T43 evaluation system. The U-Boot boot-loader will start and you will get a command prompt.
Admolition note.png If the boot settings of your CM-T43 are different than default, you may need to press and hold Ctrl-C while turning the CM-T43 on, in order to get command prompt.

Boot into the installation environment (ramdisk)

The first step in CM-T43 Yocto Linux installation is starting the installation environment (Linux kernel and Ramdisk image). This can be done using one of the following media:

Using installation environment on MMC/SD card

  • Copy kernel.img, ramdisk.dtb, ramdisk.img, zImage-cm-t43, am437x-sb-som-t43.dtb, and rootfs.tar.bz2 from Linux package for CM-T43 Yocto to the root directory on the first partition of the MMC/SD card.
  • Insert the MMC/SD card into the MMC/SD socket (P9) on the SB-SOM-T43 baseboard.

Use the following U-Boot commands to start installation environment boot: 

CM-T43 # mmc dev 0
CM-T43 # mmc rescan
CM-T43 # load mmc 0 0x88000000 ramdisk.dtb
CM-T43 # load mmc 0 0x82000000 kernel.img
CM-T43 # load mmc 0 0x88080000 ramdisk.img
CM-T43 # setenv bootargs "root=/dev/ram0 rw ramdisk_size=16384 console=ttyO0,115200n8 vram=16M ip=dhcp"
CM-T43 # bootz 0x82000000 0x88080000 0x88000000

Using installation environment from USB storage device

  • Copy kernel.img, ramdisk.dtb, ramdisk.img, zImage-cm-t43, am437x-sb-som-t43.dtb, and rootfs.tar.bz2 from Yocto Linux package for CM-T43 to the root directory on the first partition of the USB storage device.
  • Insert USB storage device into SB-SOM-T43 USB port (P6 or P26).
  • Remove MMC/SD card from the MMC/SD socket (P9) on the SB-SOM-T43 baseboard.
  • Use the following U-Boot commands to start installation environment boot:
CM-T43 # usb start
CM-T43 # load usb 0 0x88000000 ramdisk.dtb
CM-T43 # load usb 0 0x82000000 kernel.img
CM-T43 # load usb 0 0x88080000 ramdisk.img
CM-T43 # setenv bootargs "root=/dev/ram0 rw ramdisk_size=16384 console=ttyO0,115200n8 vram=16M ip=dhcp"
CM-T43 # bootz 0x82000000 0x88080000 0x88000000

Using installation environment from TFTP server

  • Connect the SB-SOM-T43 Ethernet port (P21) to your local network.
  • Put kernel.img, ramdisk.dtb, ramdisk.img, zImage-cm-t43, am437x-sb-som-t43.dtb, and rootfs.tar.bz2 from Yocto Linux package for CM-T43 to a location accessible by the TFTP server.
  • You can use U-Boot dhcp command to obtain IP address
CM-T43 # dhcp
or manually set ipaddr environment variable:
CM-T43 # setenv ipaddr <CM-T43 ip address>
  • Use the following U-Boot commands to start installation environment boot:
CM-T43 # setenv bootargs "root=/dev/ram0 rw ramdisk_size=16384 console=ttyO0,115200n8 vram=16M ip=dhcp"
CM-T43 # tftpboot 0x88000000 ramdisk.dtb
CM-T43 # tftpboot 0x82000000 kernel.img
CM-T43 # tftpboot 0x88080000 ramdisk.img
CM-T43 # bootz 0x82000000 0x88080000 0x88000000

Install Kernel and Yocto Linux Images

After the ramdisk image is loaded the Linux login prompt will appear. Login as root into the system. 

compulab login: root

Mount the installation source media

The next step is installing the kernel and rootfs images. One of the following media can be used as a source for installation:

Mount an MMC/SD Card
  • The MMC/SD card is mounted automatically under /media/mmcblk0pX. Where X is the partition number.
  • If for some reason the MMC/SD card hasn't been mounted automatically, use the following mount command:
root@compulab:~# mkdir -p /media/mmcblk0pX && mount /dev/mmcblk0pX /media/mmcblk0pX
Mount a USB Storage Device
  • The USB device is mounted automatically under /media/sdXY. Where X is the device letter and Y is the partition number.
  • If for some reason the USB storage device hasn't been mounted automatically, use the following mount command:
root@compulab:~# mkdir -p /media/sdXY && mount /dev/sdXY /media/sdXY
Mount an NFS drive
  • Connect the SB-SOM-T43 Ethernet port (P21) to your local network.
  • Copy the zImage-cm-t43, am437x-sb-som-t43.dtb and the rootfs.tar.bz2 from the Yocto Linux package for CM-T43 to a directory exported through NFS.
  • During Ramdisk image booting the CM-T43 attempts to obtain an IP address using DHCP. If from some reason the IP address has not been obtained, use the following commands to obtain IP address for the CM-T43:
    • Obtain IP using DHCP:
      root@compulab:~# ifup eth0
    • If there is no DHCP server on the network, you can set a static IP address using ifconfig:
      root@compulab:~# ifconfig eth0 <ip address>
  • Mount the NFS share containing the zImage-cm-t43, am437x-sb-som-t43.dtb and the rootfs.tar.bz2 files:
root@compulab:~# mount -o nolock <host ip>:/path/to/nfs/share /mnt/net

Install Images

  • In this subsection the term /mount/point can be:
    • /mnt/net if NFS is used
    • /media/mmcblk0pY if an MMC/SD card is used, where Y is the partition number.
    • /media/sdXY if USB storage is used, where X is the USB drive letter and Y is the partition number.
Install Images on eMMC
  • Create two partitions for the Linux kernel (FAT32 100M) and root file system (EXT4 the rest of the disk) on the eMMC.
Admolition note.png If an SD-Card is inserted in the SD card socket, eMMC will be enumerated as /dev/mmcblk1.
If an SD-Card is not inserted in the SD card socket, eMMC will be enumerated as /dev/mmcblk0. In the following instructions /dev/mmcblkX(p1,p2) refers to the eMMC. 
root@compulab:~# echo -e "n\np\n1\n2048\n204800\na\n1\nt\nc\nn\np\n2\n204801\n\nw\neof\n" | fdisk -u /dev/mmcblkX
  • Refresh the device nodes:
root@compulab:~# mdev -s && umount /dev/mmcblkXp1 && umount /dev/mmcblkXp2
  • Format the first partition with FAT32 file system:
root@compulab:~# mkfs.vfat -n boot /dev/mmcblkXp1
  • Format the second partition with EXT4 file system:
root@compulab:~# mkfs.ext4 /dev/mmcblkXp2
  • Mount both partitions:
root@compulab:~# mkdir -p /media/mmcblkXp1 && mount /dev/mmcblkXp1 /media/mmcblkXp1
root@compulab:~# mkdir -p /media/mmcblkXp2 && mount /dev/mmcblkXp2 /media/mmcblkXp2
  • Copy the zImage-cm-t43 and the am437x-sb-som-t43.dtb to the first (FAT) partition:
root@compulab:~# cp /mount/point/zImage-cm-t43 /media/mmcblkXp1; cp /mount/point/am437x-sb-som-t43.dtb /media/mmcblkXp1 && sync
  • Extract the content of rootfs.tar.bz2 onto the second partition:
root@compulab:~# tar --numeric-owner -xvpjf /mount/point/rootfs.tar.bz2 -C /media/mmcblkXp2 && sync
  • Remove MMC/SD card from SB-SOM-T43 MMC/SD card socket (if used for installation) and reboot the module.

Boot from eMMC

  • Set the bootargs environment variable:
CM-T43 # setenv bootargs "root=/dev/mmcblkXp2 rw rootfstype=ext4 rootwait console=ttyO0,115200n8"
  • Set the bootcmd environment variable and save the environment:
CM-T43 # setenv bootcmd 'mmc dev 1 && mmc rescan && load mmc 1 ${loadaddr} zImage-cm-t43 && load mmc 1 ${fdtaddr} am437x-sb-som-t43.dtb && bootz ${loadaddr} - ${fdtaddr}'
CM-T43 # saveenv
  • To boot Linux, type:
CM-T43 # boot

See also

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