~~tag>VIM4 boot-sequence MCU~~

====== VIM4 OS Boot Priority ======

VIM4 have possibility boot-up from : ''eMMC'', ''TF Card'', ''SPI-Flash''

<WRAP info >
We talking there only about 1st stage SoC boot, 
next second stage OS loading possible for any other devices like USB storage's,
NVMe etc ... and depends from ''u-boot'' configurations
</WRAP>

===== Default boot priority =====

  - TF-Card <wrap important>always highest priority</wrap>
  - eMMC
  - SPI-Flash

===== U-Boot shell usage =====
You can change the boot priority of the ''eMMC'' and ''SPI-Flash'' via the [[products:sbc:vim4:development:kbi|KBI(Khadas Boot Instructions)]] from u-boot shell

Change boot priority to: ''TF-Card'' => ''eMMC'' => ''SPI-Flash''

```shell
kvim4# kbi bootmode w emmc
```

Change boot priority to: ''TF-Card'' => ''SPI-Flash'' => ''eMMC''

```shell
kvim4# kbi bootmode w spi
```

<WRAP important >
for apply setting for next boot, need reboot device by ''RESET'' button or re-plug power cable or power-off device or [[#hot-apply-setting-changes-via-mcu-reboot|reboot via mcu]]
</WRAP>


===== Linux command-line usage =====

```sh
i2cset -f -y 6 0x18 0x20 1 # setup default eMMC boot-mode
```

```sh
i2cset -f -y 6 0x18 0x20 0 # setup SPI-flash boot-mode
```

==== Hot apply setting changes via mcu reboot ====

```sh
i2cset -f -y 6 0x18 0x91 1
```


===== OOWOW boot special shortcut =====

Hold ''FUNCTION'' and short press ''RESET'' to force boot [[:OOWOW]] service from SPI-flash, and skip other boot sources

<WRAP important>TF-card slot must be empty.</WRAP>