All COM are delivered with pre-installed U‑Boot bootloader firmware. U‑Boot supports several low-level-debugging options and file download via Ethernet (TFTP), USB or via UART/serial X/Y/Z-Modem. These files can additionally be stored into the permanent flash-memory (NAND/eMMC) to be started by command or power-on.

Further more can the user communicate with the bootloader via serial console, provided via RS232 using a `terminal-program`_.


For full documentation, incl. comprehensive command reference of U‑Boot please be referred to DENX’s online manual, as available here: The DENX U-Boot and Linux Guide (DULG)

Getting started

To communicate with the CoM’s bootloader users need to connect to it via RS232 serial port, which dependent on the baseboard either is a D-SUB9 or pin-header (see Baseboard Pinouts, or TTL Debug UART pin header) connector, where the latter requires a TTL-2-USB RS232 converter.

First steps


  1. Connect the Debug UART (D-Sub 9, TTL pin header).
  2. Start Terminal program (Terminal Settings).
  3. Connecting the 5V DC power your board will boot.
  4. Press any key” to abort the auto boot in U-Boot. (Can be pressed before message shows)


Pressing CTRL-C as this will not only abort the auto boot but also skip U-Boot hardware initilization, incl. skipping reading some variables and settings from the enviornment, thus leaving the COM in a recovery state (NOT ROM recovery!).

Terminal Connection

Terminal Progam

For terminal program following are recommended:


Under Linux all above are usually available via the distribution’s package manger.

Terminal Settings

Running there terminal program on the host PC the communication parameters used are:

Setting Value
Baud rate 115 200
Data bits 8
Parity None
Flow control None [1] [2]
[1]or software flow control (Xon/Xoff)
[2]Disable hardware handshake (RTS/CTS)

Power-On and Reset Output

After power up or reset, output of U‑Boot will appear on the console similar to this:

U-Boot 2015.10-rc2-04843-ge1be59f (Oct 23 2015 - 12:57:17 +0200)
CPU: Freescale i.MX6SOLO rev1.2 at 792 MHz
Temperature: Industrial grade (-40C to 105C) at 54C - calibration data 0x59a50669
Reset cause: POR
I2C: ready
DRAM: 256 MiB
Board: Ka-Ro TX6S-8034
VDDCORE set to 1350mV
VDDSOC set to 1350mV
NAND: 128 MiB
IPU HW Rev: 4
Baseboard: stk5-v3
MAC addr from fuse: 00:0c:c6:7c:6a:6d
Net: FEC
Hit any key to stop autoboot:  0
TX6S U-Boot >