FAQs/Howtos

This Howto section describes some basic procedures on a running Duckbill device. For build-time FAQ/Howtos, please refer to the documentation of the used BSP project called STIB.

USB recovery mode

The USB recovery mode is activated when:

  • Duckbill is powered on without a bootable image in the eMMC,
  • PSWITCH is pressed for more than five seconds while ROM boot.

Note: During USB recovery mode the Duckbill LEDs are off

Flashing

The embedded eMMC flash can be programmed via Freescale’s Manufacturing Tool MfgTool (registration required). This uses the USB recovery mode of the i.MX28. In this mode the MfgTool transfers a small software into i.MX28’s RAM, which is able to access the eMMC flash.

Requirements:

  • Windows PC with USB 2.0 interface
  • Freescale MfgTool 1 for i.MX28

Note: USB 3.0 isn’t supported by MfgTool

Necessary steps:

  • Extract the ZIP archive with the Linux image
  • Copy the complete Duckbill directory ( e.g. Duckbill2_v1_2 ) into Freescale MfgTool Profile directory ( <MfgToolInstallDir>/Profiles )
  • Start Duckbill in USB recovery mode ( at first time this triggers a driver installation )
  • Start MfgTool
  • Press the button “Scan devices”
  • After the Duckbill has been found the button on the right should be named as “Start” and green
  • Select the profile ( is the same as the directory name copied above ) which should be flashed via the drop-down list
  • Now press the button “Start” and wait until the writing process has been finished
  • Finally press the button “Stop” and disconnect Duckbill from USB

Update the Linux kernel

  • Transfer the new linux kernel image (zImage) binary to the Duckbill.
  • Replace the existing linux kernel image in /boot directory with the new one.
  • Reboot the Duckbill, so that the new kernel is used.

Update the Device Tree binary

  • Transfer the new Device Tree binary file to the Duckbill.

  • Replace the existing Device Tree binary in /boot directory with the new one.

  • Please remember, that U-Boot looks for a device specific filename when booting, so either use the same filename as of the replaced file, or adjust the U-Boot setting with:

    fw_setenv fdt_file <new-file.dtb>
sync

  • Reboot the Duckbill, so that the new Device Tree is used.

Update U-Boot on the target device from running Linux

  • Transfer the new U-Boot image file (u-boot.sb) to the Duckbill.

  • Install it with the following command:

    sdimage -f u-boot.sb -d /dev/mmcblk0
sync

Modify U-Boot environment

The BSP comes with the U-Boot tools fw_printenv and fw_setenv pre-installed. Use fw_printenv to show all or individual U-Boot environment variables and use fw_setenv to modify or delete them.

Both tools require the configuration file /etc/fw_env.config with the following content:

/dev/mmcblk0 0x20000 0x20000
/dev/mmcblk0 0x40000 0x20000

This file tells both tools where to save the both redundant U-Boot environment regions within the eMMC/SD card, and how large both areas are.

Modify kernel command line parameters

U-Boot passes kernel command line arguments to linux kernel using the U-Boot environment variable bootargs. However, on Duckbill this variable is constructed at run-time. So if you need to append some command line arguments, please extend the U-Boot variable mmcargs, e.g.:

fw_setenv mmcargs 'setenv bootargs console=${console},${baudrate} root=${mmcroot} rootwait bootsys=${bootsys} panic=1 <something to append>'
sync

Please note, that the default content of mmcargs contains variable names, so you have to quote these properly, otherwise your shell would try to expand the variables!

To make it easier during development, it is recommended to introduce a dedicated variable and to append solely a reference to it, e.g.:

fw_setenv custom_args <something to append>
fw_setenv mmcargs 'setenv bootargs console=${console},${baudrate} root=${mmcroot} rootwait bootsys=${bootsys} panic=1 ${customargs}'
sync

This way, you can focus on changing custom_args without worrying to always touch the longish mmcargs variable.

The mmcargs U-Boot variable shown above contains the factory default string used in U-Boot to build the kernel command line. So at runtime, the variable references are substituted and this results in a default kernel command line:

console=ttyAMA0,115200 root=/dev/mmcblk0p2 rootwait bootsys=1 panic=1