FPGA computer boots from the SD card

FPGA computer boots now from the SD card

This is a follow-up of my first text about 32-bit FPGA computer.

The 32-bit FPGA computer now has a kind of a hard disk. ESP32 is used as a hard disk controller (I have designed the board to work with the Arduino as well - you can see the empty socket for the Arduino to the right of the ESP32), while the SD card is used as a kind of a hard disk.

The FPGA computer with the ESP32-Arduino board is on the images above and below.

Initially, it was just the Arduino:

Since the FPGA computer is designed to boot from the serial port, I have created a kind of a hard disk controller, which consists of an ESP32 and SD card reader. When started, ESP32 lists files in the root folder of the SD card, and if it finds the file "BOOT.BIN", it reads it and sends the content to the FPGA computer over the serial port, using the Raspbootin protocol (as described in one of my previous posts).

The video above shows the boot from the powerup. Next video shows boot from the reset.

The code is available at the github.

This is the schematics:

The main idea is that the controller behaves just like the PC from which the FPGA computer initally gets its boot code. During the powerup, the FPGA computer will try to load the boot code from the serial interface, using a modified Raspbootin protocol. On the other side of the serial cable, there can be a PC with the corresponding Raspbootin client, or, just like in this case, the microcontroller, which has the following functionality:

1. wait for the Raspbootin start sequence,
2. look for the BOOT.BIN file in the SD card, and
3. send that file content over serial cable, using the Raspbootin protocol.

The FPGA computer would then boot from the loaded BOOT.BIN file. The BOOT.BIN file is the assembled file obtained using the custom assembler also available on my github page.

Conclusion

With this board, the FPGA-based computer can now boot from the SD card. Next step would be to extend the code so it would be used as a real SD controller, allowing the FPGA computer to open files, read, write, delete, etc.

Odroid XU4 boot from hard disk

I have Odroid XU4 computer. It is a nice piece of machine. It has 8 cores, Gigabit Ethernet, USB3.0. It can boot from uSD card, or eMMC module. However, I have experienced frequent uSD card crashes, so severe, that the Odroid wouldn't boot afterwards. It would happen when Odroid does some intensive write to the file system. It would simply mess up the file system beyond repair.

That is why I have decided to find instructions how to boot this device from a hard disk.

First of all, you cannot make your Odroid XU4 completely boot from the hard disk. It will start the boot process from the uSD card, and then it will mount the root file system on the hard disk, instead on the uSD card.

There is a nice post on the official Odroid forum. It says that you need to write the image on your uSD card and then boot the Odroid. When it boots successfully, you can then connect the external USB hard disk. Then you need to format that external hard disk to ext4 file system:

mkfs.ext4 /dev/sda1

Now you need to copy the content of the uSD root partition to the external hard disk:

mkdir /tmp/sda1
mount /dev/sda1 /tmp/sda1
rsync -avx / /tmp/sda1
umount /dev/sda1

After that, type blkid to see UUIDs of all disks connected to your Odroid. The output would be like this:

/dev/sda1: UUID="86135-2ba3-45cf-bda0-317b" TYPE="ext4" PARTUUID="ab57-01"
/dev/mmcblk0: PTUUID="3ceda53" PTTYPE="dos"
/dev/mmcblk0p1: SEC_TYPE="msdos" LABEL="boot" UUID="5A5A-6868" TYPE="vfat" PARTUUID="3cd53-01"
/dev/mmcblk0p2: LABEL="rootfs" UUID="e139-fe3-99859" TYPE="ext4" PARTUUID="3cd53-02"

Hard disk is /dev/sda1. You need to remember its UUID, since you need to put it in two places: /media/boot/boot.ini file, and /etc/fstab file (before unmounting the temporary mount, it was: /tmp/sda1/etc/fstab).

Make copies of both files, then edit the /media/boot/boot.ini file first. Find the line in which the root file system is mounted:

setenv bootrootfs “console=tty1
console=ttySAC2,115200n8 root=UUID=e139-fe3-99859 rootwait ro”

Substitute the original UUID with the UUID of the hard disk. This way, the Odroid will continue boot from the hard disk instead from the uSD card:

setenv bootrootfs “console=tty1

console=ttySAC2,115200n8 root=UUID=86135-2ba3-45cf-bda0-317b rootwait ro”

Next, open the /etc/fstab file (before unmounting the temporary mount, it was: /tmp/sda1/etc/fstab). Change the original UUID to the UUID of the hard disk:

UUID=86135-2ba3-45cf-bda0-317b / ext4 errors=remount-ro,noatime 0 1
LABEL=boot /media/boot vfat defaults 0 1

With this change, you will have the external hard disk permanently mounted.

I have written couple of instructions about setting up Raspberry Pi here.