8.8. TFTP and U-Boot

TFTP and U-Boot provides a simple way to test RTEMS on a network capable target. The RTEMS Tester starts a TFTP server for each test and the target’s boot monitor, in this case U-Boot request a file, any file, which the TFTP server supplies. U-Boot loads the executable and boots it using a standard U-Boot script.

RTEMS Tester using TFTP and U-Boot

RTEMS Tester using TFTP and U-Boot.

The Figure RTEMS Tester using TFTP and U-Boot. figure shows the structure and control flow of the RTEMS Tester using TFTP and U-boot. The executables are built and the rtems-test command is run from the top of the build directory.

This test mode can only support a single test job running at once. You cannot add more test target hardware and run the tests in parallel.

8.8.1. Target Hardware

The RTEMS Tester TFTP and U-Boot method of testing requires:

  1. A target with network interface.
  2. U-Boot, iPXE or similar boot loader with network driver support for your target hardware and support for the TFTP protocol.
  3. Network power of IO switch.
  4. Network DHCP server.
  5. Console interface cable that matches your target’s console UART interface.
  6. Telnet terminal server. See Chapter 8 Section 5 - Consoles.

The network power or IO switch is a device that can control power or an IO pin over a network connection using a script-able protocol such as Telnet or curl. This device can be used with the target control commands. U-Boot Set Up

Obtain a working image of the U-Boot boot loader for your target. We suggest you follow the instructions for you target.

Configure U-Boot to network boot using the TFTP protocol. This is U-Boot script for a Zedboard:

uenvcmd=echo Booting RTEMS Zed from net; set autoload no; dhcp; set serverip; tftpboot zed/rtems.img; bootm; reset;

The load address variable loadaddr is specific to the Zedboard and can be found in the various examples scripts on the internet. The script then sets U-Boot environment variable autoload to no causing DHCP to only request a DHCP lease from the DHCP server. The script sets the serverip to the host that will be running the RTEMS Tester then issues a TFTP request. The file name can be anything because the RTEMS Tester ignores it sending the executable image under test. Finally the script boots the download executable and if that fails the catch all reset resets the board and starts the boot process over.

Test the target boots and U-Boot runs and obtains a valid DHCP lease. Manually connect the console’s telnet port.

8.8.2. BSP Configuration

The BSP’s configuration file must contain the standard fields:

  • bsp
  • arch
  • jobs - Must be set to 1.
  • tester - Set to %{_rtscripts}/tftp.cfg

For example the Zedboard’s configuration is:

bsp    = xilinx_zynq_zedboard
arch   = arm
jobs   = 1
tester = %{_rtscripts}/tftp.cfg

The TFTP configuration supports the following field’s:

The target’s tty console. For telnet this is a host and port pair written in the standard networking format, for example serserver:12345.
The number of restarts before the test is considered invalid.
The target reset regular expression. This is a Python regular expression used to filter the console input. If a match is made something has happened during the boot process that requires a reset. The target_reset_command is issued to perform the reset. This field is typically looks for boot loader error messages that indicate the boot process as failed.
The target start regular expression. This also a Python regular expression to filter the console input to detect if a target has reset. If a board crashes running a test or at any point in time and reset this filter detects this as happened and end the test with a suitable result.
The target on command is a host shell command that is called before the first test. This command powers on a target. Targets should be left powered off when not running tests or the target may request TFTP downloads that are for another target interfering with those test results. We recommend you implement this command as a target off command, a pause, then a target on command.
The target off command is a host shell command that is called after the last test powering off the target.
The target reset command is a host shell command that is called when the target needs to be reset. This command can power cycle the target or toggle a reset signal connected to the target. If you are power cycling a target make sure you have a suitable pause to let the target completely power down.
The target pretest command is a host shell comment that is called before the test is run

The commands in the listed fields can include parameters that are substituted. The parameters are:

The BSP architecture
The BSP’s name
The executable name.
. The
@ARCH is the


Some of these field are normally provided by a user’s configuration. To do this use:

requires = bsp_tty_dev, target_on_command, target_off_command, target_reset_command

The requires value requires the user provide these settings in their configuration file.

The Zedboard’s configuration file is:

bsp                = xilinx_zynq_zedboard
arch               = arm
jobs               = 1
tester             = %{_rtscripts}/tftp.cfg
test_restarts      = 3
target_reset_regex = ^No ethernet found.*|^BOOTP broadcast 6.*|^.+complete\.+ TIMEOUT.*
target_start_regex = ^U-Boot SPL .*
requires           = target_on_command, target_off_command, target_reset_command, bsp_tty_dev

The target_start_regex searches for U-Boot’s first console message. This indicate the board can restarted.

The target_reset_regex checks if no ethernet interface is found. This can happen if U-Boot cannot detect the PHY device. It also checks if too many DHCP requests happen and finally a check is made for any timeouts reported by U-Boot.

An example of a user configuration for the Zedboard is:

bsp_tty_dev            = selserver:12345
target_pretest_command = zynq-mkimg @EXE@
target_exe_filter      = /\.exe/.exe.img/
target_on_command      = power-ctl toggle-on 1 4
target_off_command     = power-ctl off 1
target_reset_command   = power-ctl toggle-on 1 3

8.8.3. TFTP Sequences

Running a large number of tests on real hardware exposes a range of issues and RTEMS Tester is designed to be tolerant of failures in booting or loading that can happen, for example a hardware design. These sequence diagrams document some of the sequences that can occur when errors happen.

The simplest sequence is running a test. The target is powered on, the test is loaded and executed and a pass or fail is determined:

Test Pass and Fail Sequence

Test Pass and Fail Sequences

The target start filter triggers if a start condition is detected. This can happen if the board crashes or resets with no output. If this happens repeatedly the test result is invalid:

Target Start Filter Trigger

Target Start Filter Trigger

The reset filter triggers if an error condition is found such as the bootloader not being able to load the test executable. If the filter triggers the target_reset_command is run:

Target Reset Filter Trigger

Target Reset Filter Trigger

If the RTEMS Tester does not detect a test has started it can restart the test by resetting the target. The reset command can toggle an IO pin connected to reset, request a JTAG pod issue a reset or turn the power off and on:

Target Timeout

Target Timeout