# Raspberry Pi 4 Model B - Yocto 4.0 "kirkstone" and earlier

**URL:** <https://hub.mender.io/t/raspberry-pi-4-model-b-yocto-4-0-kirkstone-and-earlier/889>\
**Category:** Yocto Project\
**Tags:** yocto, raspberry, warrior, raspberry-pi-4, zeus, dunfell, kirkstone\
**Created:** [August 6, 2019, 6:53pm UTC](https://hub.mender.io/t/raspberry-pi-4-model-b-yocto-4-0-kirkstone-and-earlier/889 "2019-08-06T18:53:21Z")\
**Posts on this page:** 1\
**Showing post:** 6

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**Author:** ![mikhailtchernychev](https://yyz2.discourse-cdn.com/flex036/user_avatar/hub.mender.io/mikhailtchernychev/32/1023_2.png) [@mikhailtchernychev](https://hub.mender.io/u/mikhailtchernychev)\
**Post date:** [September 14, 2020, 4:02pm UTC](https://hub.mender.io/t/raspberry-pi-4-model-b-yocto-4-0-kirkstone-and-earlier/889/6 "2020-09-14T16:02:45Z")

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This is Raspberry Pi 4 model B 8GB.

I think the issue is the boot script. It might be trying to load wrong or non-existing kernel.

After I re-named this file (boot.scr) I was able to get into U-boot interactive prompt via UART  
and the attached monitor.

Enabling UART kernel output for model 4 B is different from previous models,  
it is not sufficient to change config.txt The full procedure is here

> **[Teach, Learn, and Make with Raspberry Pi – Raspberry Pi](https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2711_bootloader_config.md)**

I also found that sometimes I have to send few chars from host computer at the moment when  
board is powered up. It is weird.

All stock images boot, minimal buildroot image boots, yocto example without mender does.  
Mender downloadable image boots.

Mender compiled image (mender-convert, mender with buildroot, mender with yocto) do not.

Mender-convert image allows serial interactive u-boot if boot.scr is renamed.

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