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Image Flashing Guide

Milk-V Megrez​

Preparation​

Hardware Requirements​

  • Milk-V Megrez
  • USB A to C / USB C to C Cable
  • DC 12V / ATX PSU
  • eMMC module / M.2 SATA SSD / PCI-E SSD (adapter card required for M.2 NVMe SSD) / microSD card
    • You can choose any of the storage devices as boot media, but you can only use one at a time.
  • (Optional) Keyboard, mouse, monitor, ethernet cable
  • (Optional) M.2 SDIO Wi-Fi Module
  • (Optional) A USB drive formatted in FAT32 or EXT4 to upgrade firmware
    • Or you may use dhcp or tftpboot instead, which requires ethernet connection and a TFTP server setup on your computer
  • (Optional) A M.2 SATA or M.2 NVMe / PCI-E SSD to USB enclosure
    • For flashing the image to SSD
  • (Optional) microSD card reader
    • For flashing the image to microSD card

Image Downloads​

For bootloader, boot and root images, download from here.

  • BootFS: boot-rockos-*.ext4.zst
  • RootFS: root-rockos-*.ext4.zst
  • For SD Card and SSD: sdcard-rockos-*.img.zst
  • Bootloader: bootloader_secboot_ddr5_milkv-megrez.bin

After downloading, please extract the boot and rootfs files.

If you want to upgrade bootchain via a USB drive, copy the bootloader_secboot_ddr5_milkv-megrez.bin file into the drive's first FAT32/EXT4 partition.

On Linux, install zstd and decompress the iamge.

On Windows, you can use tools like 7-zip or Nanazip.

Flashing Image​

First of all we should upgrade the firmware, a.k.a. bootchain for EIC7700X boards.

In short, you need to load the firmware into RAM, then run es_burn to write the firmware to onboard SPI Flash.

To load the bootchain file, you have a few options:

  • From an internal or external storage device
    • ext4load
    • fatload
  • From network / LAN
    • tftpboot
    • dhcp
  1. Connect the onboard USB Type-C "Debug" port to your computer.

You will see a CH340 USB to UART serial device showing up.

  1. Open the UART serial terminal.

On Linux you can use tools like tio, minicom and more.

On Windows there are PuTTY, SimplySerial and more.

The default baud rate is 115200.

  1. Now plug in the power. Megrez should automatically power on.

Make sure your boot device is properly installed before powering on.

If you want to upgrade via a USB drive, plug it in before powering on. Make sure you plugged into the two ports near the 3.5mm ports, otherwise it might not be picked up in U-Boot.

  1. While the console prompts Autoboot in 5 seconds, press s to stop the autoboot.
Upgrade via USB drive​
  1. Check if the USB Drive is detected: usb info

If you plugged the USB drive after boot, you need usb reset to rescan USB devices.

2.1. If your drive is FAT32: fatload usb 0 0x90000000 bootloader_secboot_ddr5_milkv-megrez.bin

2.2. If your drive is EXT4: ext4load usb 0 0x9000000 0bootloader_secboot_ddr5_milkv-megrez.bin

  1. Flash the firmware and reboot: es_burn write 0x90000000 flash; reset

  2. After rebooting, it is recommended to reset U-Boot env vars to default and save:

env default -a -f; env save; reset

Other wise you might see your MAC address is regenerated on every boot.

Upgrade via TFTP​

Set up a TFTP Server.

For Windows you may use TFTPd64, for Linux you may use tftp-hpa, atftp, or even dnsmasq has a TFTP server built in.

Please check your distros' documations for usage.

Or you may want to check out Arch Wiki here.

Make sure the TFTP server is serving the bootloader_secboot_ddr5_milkv-megrez.bin file at the root directory.

Then check your computer's LAN IP.

Make sure the board is plugged in to ethernet.

After interrupting the autoboot, type:

dhcp 0x90000000 $hostIPaddr:bootloader_secboot_ddr5_milkv-megrez.bin
es_burn write 0x90000000 flash; reset

As said above, it is recommended to reset U-Boot env vars to default and save after upgrading:

env default -a -f; env save; reset

Other wise you might see your MAC address is regenerated on every boot.

Flash to eMMC via fastboot​

After upgrading the bootchain, power on the board, type s to interrupt autoboot, then following these steps:

  1. In U-Boot console: fastboot usb 0

  2. Find the RECOVERY switch beside the DC barrel jack. Flip it to RECOVERY mode. Your computer should pick up a USB download gadget / Android Bootloader Interface.

  3. Use fastboot to flash the firmware.

(On Linux, you'll need sudo, or add VID:PID 3452:7700 to your udev rules.)

fastboot flash boot boot-rockos-20250423-145338.ext4
fastboot flash root root-rockos-20250423-145338.ext4

  1. Wait for the flashing process to complete. After that, press Ctrl+C in U-Boot console, then type reset to reboot.

  2. You're good to go.

note

Although U-Boot also supports fastboot udp to flash via network, but this would be much slower.

Flashing via network is generally not recommended, unless you're doing it remotely and cannot flip the switch.

Flash to SSD or microSD​

Just use etcher or dd to write the sdcard image into SSD or microSD.

For Windows users, Rufus is also okay.

sudo dd if=sdcard-rockos-20250423-145338.img of=/dev/sdX bs=1M status=progress; sync
tip

Since the bootloader is inside the onboard SPI Flash, if you have any troubles booting from microSD or SSD, update the bootloader first and then retry.

Other Notes​

It is recommended to do a system upgrade after booting into the system.

sudo apt update; sudo apt upgrade -y; sudo reboot

Default username and password are both: debian

SiFive HiFive Premier P550​

Hardware requirements​

  • HiFive Premier P550
  • DC 12V / ATX PSU
  • SATA SSD / PCI-E SSD (adapter card required for M.2 NVMe SSD) / microSD card
    • You can choose any of the storage devices as boot media, but you can only use one at a time.
  • (Optional) Keyboard, mouse, monitor, ethernet cable
  • (Optional) M.2 SDIO Wi-Fi Module
  • (Optional) A USB drive formatted in FAT32 or EXT4 to upgrade firmware
    • Or you may use dhcp or tftpboot instead, which requires ethernet connection and a TFTP server setup on your computer
  • (Optional) A M.2 SATA or M.2 NVMe / PCI-E SSD to USB enclosure
    • For flashing the image to SSD
  • (Optional) microSD card reader
    • For flashing the image to microSD card

Bootloader​

First, establish a serial connection to the board. Once the cables are correctly connected, the board will be listed as four UARTs.

tip

This chart below is for SiFive HiFive Premier P550 only, while other boards might have different.

Following Section 2.1.1.1 of the MCU User Manual, set the ttyUSB2 as the connection path in minicom, and set the baud rate to 115200.

No.Device
00SOC JTAG (eic7700x mcpu)
01MCU JTAG (stm32)
02SOC UART (eic7700x uart0)
03MCU UART (stm32 uart3)
sudo minicom -D /dev/ttyUSB2 -b 115200

Insert the prepared USB drive containing the bootloader file.

After pressing the power button to boot, observe the minicom window and interrupt the U-Boot booting by pressing Ctrl+C or enter.

Execute the following commands to check the files on the USB drive:

usb start

fatls usb 0 / # If multiple files are present on the USB drive, please confirm the storage path of the bootloader file.

After verifying the correct files on the USB drive, execute the following commands:

fatload usb 0 0x90000000 bootloader_secboot_ddr5_hifive-p550.bin

es_burn write 0x90000000 flash

After rebooting, interrupt the U-Boot booting again and execute the partitioning command (required for the first flash to allocate sufficient space for the boot/root images).

reset
# Interrupt U-Boot startup
run gpt_partition

Flashing the Image to eMMC​

Connect the board to the host system using both the USB Type A to USB Type C and USB Type A to USB Type A cables.

According to Section 3.1.6 of the official user manual:

  • Insert the USB Type A to USB Type A cable into the upper port of the dual USB Type-A connector labeled as #10.
  • Insert the USB Type A to USB Type C cable into the Type-C USB connector labeled as #15.

Boot & Rootfs​

After starting and interrupting the machine, enter the following command to enter fastboot mode. (Make sure to disconnect the USB Type A to USB Type A cable beforehand to avoid circuit or communication conflicts.)

fastboot usb 0

Open another terminal on the host and execute the following flashing commands:

sudo fastboot flash boot boot-eswin_evb-20241024-145708.ext4   # Flash boot
sudo fastboot flash root root-eswin_evb-20241024-145708.ext4   # Flash rootfs
# Ensure the file paths are correct; flashing time may take 10 minutes

Return to the minicom terminal, press Ctrl+C or enter to exit fastboot mode, and execute reset to reboot the machine.

At this point, the RockOS image flashing is complete.