This post explains how to connect to the Cortex-A9 debug serial of your UDOO Neo to control the U-Boot bootloader, watch your Linux kernel boot, and eventually get a login.


Required material

  • One UDOO Neo Full
  • One 8GB microSD Card formatted with a bootable image for your UDOO Neo
  • One USB-to-TTL Serial Cable (3.3V level)
  • One 10-mil male-to-male pin header strip
  • One laptop with a terminal emulator installed
    • Example: PuTTY on MS Windows
  • A 5Vdc power supply for your UDOO Neo
    • Tested withh a USB battery pack plus a USB to Micro-USB cable

UDOO Neo - Cortex A9 Serial Debug Configuration

  • Connect to UART_1 (Cortex A9 serial debug)
  • Serial Port Parameters: 115200,8,n,1

Wiring Diagram

Connect the TTL-level pins of the USB-to-TTL serial cable to your UDOO Neo as follows:

Dongle Pin UDOO Neo Pin Signal

Detail on UART_1 connections

Detail on UART_1 connections

Trying UDOOBuntu_neo_v2.0beta3 - Step-by-step instructions

  • Format a 8GB MicroSD Card with Udoobuntu2_beta3
  • Plug the MicroSD Card into the MicroSD slot of your UDOO Neo
  • Connect the USB plug of the USB-to-TTL dongle on your laptop
  • Identify the serial port that is exposed by the USB-to-TTL dongle on your laptop
    • I.e. on MS Windows: Start > Computer > Properties > Device Manager then look under “Ports (COM & LPT)”
  • Start the terminal emulator on your laptop (parameters: COMxx:115200,8,n,1)
    • For convenience you may create a logfile of the data exchanged on the serial console
  • Power-up the board by plugging the Micro-USB cable of the battery pack into the Micro-USB connector of your UDOO Neo
  • Watch the U-Boot and kernel boot messages on the serial console

Sample logfile: 20151107-1106-udoobuntu2_beta3-udooneo.txt