UP Squared

Overview

UP² (UP Squared) is an ultra compact single board computer with high performance and low power consumption. It features the latest Intel® Apollo Lake Celeron™ and Pentium™ Processors with only 4W of Scenario Design Power and a powerful and flexible Intel® FPGA Altera MAX 10 onboard.

UP Squared

Up Squared (Credit: https://up-board.org)

This board configuration enables kernel support for the UP Squared board.

Note

This board configuration works on all three variants of UP Squared boards containing Intel® Pentium™ SoC, Intel® Celeron™ SoC, or Intel® Atom™ SoC.

Hardware

General information about the board can be found at the UP Squared website.

Supported Features

In addition to the standard architecture devices (HPET, local and I/O APICs, etc.), Zephyr supports the following Apollo Lake-specific SoC devices:

  • HSUART
  • GPIO
  • I2C

HSUART High-Speed Serial Port Support

The Apollo Lake UARTs are NS16550-compatible, with “high-speed” capability.

Baud rates beyond 115.2kbps (up to 3.6864Mbps) are supported, with additional configuration. The UARTs are fed a master clock which is fed into a PLL which in turn outputs the baud master clock. The PLL is controlled by a per-UART 32-bit register called PRV_CLOCK_PARAMS (aka the PCP), the format of which is:

[31] [30:16] [15:1] [0]
enable m n toggle

The resulting baud master clock frequency is (n/m) * master.

Typically, the master clock is 100MHz, and the firmware by default sets the PCP to 0x3d090240, i.e., n = 288, m =  15625, which results in the de-facto standard 1.8432MHz master clock and a max baud rate of 115.2k. Higher baud rates are enabled by changing the PCP and telling Zephyr what the resulting master clock is.

Use devicetree to set the value of the PRV_CLOCK_PARAMS register in the UART block of interest. Typically a devicetree overlay file would be present in the application directory (specific to the board, such as up_squared.overlay or gpmrb.overlay), with contents like this:

/ {
    soc {
        uart@0 {
            pcp = <0x3d090900>;
            clock-frequency = <7372800>;
            current-speed = <230400>;
        };
    };
};

The relevant variables are pcp (the value to use for PRV_CLOCK_PARAMS), and clock-frequency (the resulting baud master clock). The meaning of current-speed is unchanged, and as usual indicates the initial baud rate.

GPIO

GPIOs are exposed through the HAT header, and can be referred using predefined macros such as UP2_HAT_PIN3. The physical pins are connected to the on-board FPGA acting as level shifter. Therefore, to actually utilize these GPIO pins, the function of the pins and directions (input/output) must be set in the BIOS. This can be accomplished in BIOS, under menu Advanced, and option HAT Configurations. When a corresponding pin is set to act as GPIO, there is an option to set the direction of the pin. This needs to be set accordingly for the GPIO to function properly.

Connections and IOs

Refer to the UP Squared website and UP Squared Pinout website for connection diagrams.

Programming and Debugging

Use the following procedures for booting an image on a UP Squared board.

Creating a GRUB2 Boot Loader Image from a Linux Host

If you are having problems running an application using the preinstalled copy of GRUB, follow these steps to test on supported boards using a custom GRUB.

  1. Install the requirements to build GRUB on your host machine.

    On Ubuntu, type:

    $ sudo apt-get install bison autoconf libopts25-dev flex automake \
    pkg-config gettext autopoint
    

    On Fedora, type:

    $ sudo dnf install gnu-efi bison m4 autoconf help2man flex \
    automake texinfo gettext-devel
    
  2. Clone and build the GRUB repository using the script in Zephyr tree, type:

    $ cd $ZEPHYR_BASE
    $ ./boards/x86/common/scripts/build_grub.sh x86_64
    
  3. Find the binary at $ZEPHYR_BASE/boards/x86/common/scripts/grub/bin/grub_x86_64.efi.

Build Zephyr application

  1. Build a Zephyr application; for instance, to build the hello_world application on UP Squared:

    # From the root of the zephyr repository
    west build -b up_squared samples/hello_world
    

    Note

    A stripped project image file named zephyr.strip is automatically created in the build directory after the application is built. This image has removed debug information from the zephyr.elf file.

Preparing the Boot Device

Prepare a USB flash drive to boot the Zephyr application image on a UP Squared board.

  1. Refer to the UP Squared Serial Console Wiki page for instructions on how to connect for serial console.

  2. Format the USB flash drive as FAT32.

    On Windows, open File Explorer, and right-click on the USB flash drive. Select Format.... Make sure in File System, FAT32 is selected. Click on the Format button and wait for it to finish.

    On Linux, graphical utilities such as gparted can be used to format the USB flash drive as FAT32. Alternatively, under terminal, find out the corresponding device node for the USB flash drive (for example, /dev/sdd). Execute the following command:

    $ mkfs.vfat -F 32 <device-node>
    

    Important

    Make sure the device node is the actual device node for the USB flash drive. Or else you may erase other storage devices on your system, and will render the system unusable afterwards.

  3. Create the following directories

    efi

    efi/boot

    kernel

  4. Copy the kernel file zephyr/zephyr.strip to the $USB/kernel folder.

  5. Copy your built version of GRUB to $USB/efi/boot/bootx64.efi

  6. Create $USB/efi/boot/grub.cfg containing the following:

    set default=0
    set timeout=10
    
    menuentry "Zephyr Kernel" {
       multiboot /kernel/zephyr.strip
    }
    

Booting the UP Squared Board

Boot the UP Squared board from the boot device using GRUB2 via USB flash drive.

  1. Insert the prepared boot device (USB flash drive) into the UP Squared board.

  2. Connect the board to the host system using the serial cable and configure your host system to watch for serial data. See https://wiki.up-community.org/Serial_console.

    Note

    On Windows, PuTTY has an option to set up configuration for serial data. Use a baud rate of 115200.

  3. Power on the UP Squared board.

  4. When the following output appears, press F7:

    Press <DEL> or <ESC> to enter setup.
    
  5. From the menu that appears, select the menu entry that describes that particular type of USB flash drive.

    GRUB2 starts and a menu shows entries for the items you added to the file grub.cfg.

  6. Select the image you want to boot and press Enter.

    When the boot process completes, you have finished booting the Zephyr application image.

    Note

    You can safely ignore this message if it appears:

    WARNING: no console will be available to OS
    

Booting the UP Squared Board over network

Build Zephyr image

  1. Follow Build Zephyr application steps to build Zephyr image.

Prepare Linux host

  1. Follow Creating a GRUB2 Boot Loader Image from a Linux Host steps to create grub binary.

  2. Install DHCP, TFTP servers. For example dnsmasq

    $ sudo apt-get install dnsmasq
    
  3. Configure DHCP server. Configuration for dnsmasq is below:

    # Only listen to this interface
    interface=eno2
    dhcp-range=10.1.1.20,10.1.1.30,12h
    
  4. Configure TFTP server.

    # tftp
    enable-tftp
    tftp-root=/srv/tftp
    dhcp-boot=grub_x86_64.efi
    

    grub_x86_64.efi is a grub binary created above.

  5. Create the following directories inside TFTP root /srv/tftp

    $ sudo mkdir -p /srv/tftp/EFI/BOOT
    $ sudo mkdir -p /srv/tftp/kernel
    
  6. Copy the Zephyr image zephyr/zephyr.strip to the /srv/tftp/kernel folder.

    $ sudo cp zephyr/zephyr.strip /srv/tftp/kernel
    
  7. Copy your built version of GRUB to /srv/tftp/grub_x86_64.efi

  8. Create /srv/tftp/EFI/BOOT/grub.cfg containing the following:

    set default=0
    set timeout=10
    
    menuentry "Zephyr Kernel" {
       multiboot /kernel/zephyr.strip
    }
    
  9. TFTP root should be looking like:

    $ tree /srv/tftp
    /srv/tftp
    ├── EFI
    │   └── BOOT
    │       └── grub.cfg
    ├── grub_x86_64.efi
    └── kernel
        └── zephyr.strip
    
  10. Restart dnsmasq service:

    $ sudo systemctl restart dnsmasq.service
    

Prepare UP Squared board for network boot

  1. Enable PXE network from BIOS settings.

    Advanced -> Network Stack Configuration -> Enable Network Stack -> Enable Ipv4 PXE Support
    
  2. Make network boot as the first boot option.

    Boot -> Boot Option #1 : [Network]
    

Booting UP Squared

  1. Connect the board to the host system using the serial cable and configure your host system to watch for serial data. See https://wiki.up-community.org/Serial_console.

  2. Power on the UP Squared board.

  3. Verify that the board got an IP address:

    $ journalctl -f -u dnsmasq
    dnsmasq-dhcp[5386]: DHCPDISCOVER(eno2) 00:07:32:52:25:88
    dnsmasq-dhcp[5386]: DHCPOFFER(eno2) 10.1.1.28 00:07:32:52:25:88
    dnsmasq-dhcp[5386]: DHCPREQUEST(eno2) 10.1.1.28 00:07:32:52:25:88
    dnsmasq-dhcp[5386]: DHCPACK(eno2) 10.1.1.28 00:07:32:52:25:88
    
  4. Verify that network booting is started:

    $ journalctl -f -u dnsmasq
    dnsmasq-tftp[5386]: sent /srv/tftp/grub_x86_64.efi to 10.1.1.28
    dnsmasq-tftp[5386]: sent /srv/tftp/EFI/BOOT/grub.cfg to 10.1.1.28
    dnsmasq-tftp[5386]: sent /srv/tftp/kernel/zephyr.strip to 10.1.1.28
    
  5. When the boot process completes, you have finished booting the Zephyr application image.