Embedded Linux¶

In this step, we will execute a sample Linux provided by Terasic. For this, we will need to program an SD card with the image. Let's perform the following steps for this:

1. Download and write the Terasic Image (.iso) to the SD card
2. Insert the SD card into the FPGA
3. Connect the USB to the UART port (near the Ethernet port)
4. Connect the power supply
5. Connect to the terminal via UART
6. Run commands

Getting Started¶

To follow this tutorial, you will need:

• Hardware: DE10-Standard and SD card
• Software: Quartus 18.01
• Git submission: folder Lab1_HPS_Infra

Standard Image (SD card)¶

We will use an already generated image (.iso) for the board's ARM, which already has the entire system necessary to run Linux on the HPS (including bootloader, kernel, and filesystem). This image was created with the Linaro distribution.

Extract the de10_standard_linux_console.img file from the zipped file, this .img is a bit by bit copy of what should be saved to the SD card. Now we have to copy the img to the memory card.

When we insert an external disk into Linux, it associates it with a 'device' in the /dev/ directory. To know the name of the device assigned to the SD card, we can use the dmesg command, which displays the operating system log, and there we can see what the last detected hardware was and which device was assigned:

$ dmesg | tail
[ 4789.207972] mmc0: new ultra high speed SDR50 SDHC card at address aaaa
[ 4789.211680] mmcblk0: mmc0:aaaa SL16G 14.8 GiB 
[ 4789.215857]  mmcblk0: p1 p2 p3
[ 4988.443942]  mmcblk0: p1 p2 p3

The dmesg log shows that my SDCARD was allocated to: /dev/mmclk0, your Linux may use a different name!

Now let's transfer the .iso to the SD card (this is different from copying the file to the SD card!)

$ sudo dd bs=4M if=de10_standard_linux_console.img of=DEVICE conv=fsync status=progress
$ sync

The sync command is necessary so that the kernel can flush the cache, actually writing all the data that was addressed to it on the SD card. This step may take some time.

Now just mount the newly written SD card on your Linux, and we should see two visible partitions:

• 524 MiB: FAT32
  • Uboot configuration script; Compressed Kernel; Device Tree Blob file
  • u-boot.scr; zImage; socfpga.dtb
• 3.3 GiB:
  • Filesystem (/)

And another partition that is not visible (contains the preloader and the uboot), to view:

$ sudo fdisk -l /dev/mmcblk0 
...
Device         Boot   Start     End Sectors  Size Id Type
/dev/mmcblk0p1         4096 1028095 1024000  500M  b W95 FAT32
/dev/mmcblk0p2      1028096 7376895 6348800    3G 83 Linux
/dev/mmcblk0p3         2048    4095    2048    1M a2 unknown
...

Note that partition 3 (mmcblk0p3) is of the unknown type (a2) and has 1M of space. This is where the preloader and the uboot are saved.

USB - UART¶

The UART-to-USB port is a connector that allows access to the HPS serial output via the serial port. On Linux, the driver is recognized automatically, while on Windows, you will need to manually install the serial driver.

Once connected on the Linux host, we verify that it was mapped to a device of the serial type (in my case, named ttyUSB0):

$ dmesg | tail 
....
[80473.426308] ftdi_sio 1-2:1.0: FTDI USB Serial Device converter detected
[80473.426333] usb 1-2: Detected FT232RL
[80473.426456] usb 1-2: FTDI USB Serial Device converter now attached to ttyUSB0
...

To connect to this port, we need to use a terminal emulator program. In this case, we will use screen (check if it's installed). Note that the following command should be modified for the device (/dev/ttyxxx) to which your Linux associated the UsSB-Serial port, extracted from dmesg.

$ screen /dev/ttyUSB0 115200,cs8

Linux¶

Now we can log in to the Linux running on the device, for this use:

• user: root
• pass:

Great! Now let's discover how to create programs for this Linux!