# Uart stopped working after update from Thud to Warrior
**URL:** https://hub.mender.io/t/uart-stopped-working-after-update-from-thud-to-warrior/1201
**Category:** General Discussions
**Tags:** yocto, raspberry-pi-3
**Created:** [October 30, 2019, 12:00am UTC](https://hub.mender.io/t/uart-stopped-working-after-update-from-thud-to-warrior/1201 "2019-10-30T00:00:51Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@TimFroehlich](https://hub.mender.io/u/TimFroehlich)
#### Post date: [October 30, 2019, 12:00am UTC](https://hub.mender.io/t/uart-stopped-working-after-update-from-thud-to-warrior/1201/1 "2019-10-30T00:00:51Z")
So I was excited to upgrade my build to Warrior, and it’s gone mostly well, but I’m having one problem that’s worrying me a bit. I have a serial port attached to the Uart for debugging and after the mender update from Thud to Warrior it stops working. It’ll show the U-boot startup, but the last thing it’ll show before booting is “Launching Kernel”. I know the board is booting properly because I can still log in via alternate means. This only happen after a mender update from my old image to my new one. If I flash a new image to the SD card from scratch, the serial port works fine. Also, if I copy the boot partition from my a working Warrior image to the mender-updated broken one, the serial port works fine too.
So that makes me think there’s something that was changed in the dtb or firmware that the new Warrior builds are expecting. My other tests have been going well, but I’m still worried that there might be some other hardware failure caused by this. Is this a valid worry? Is there a method of updating the boot partition that I missed?
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### Author:  [@kacf](https://hub.mender.io/u/kacf)
#### Post date: [October 30, 2019, 6:47am UTC](https://hub.mender.io/t/uart-stopped-working-after-update-from-thud-to-warrior/1201/2 "2019-10-30T06:47:17Z")
A comparison of `fw_printenv` from a working device and a non-working one would be useful. Could be that some arguments have changed that affect both boot loader and kernel, and when upgrading with Mender, only the kernel is touched.
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### Author:  [@mirzak](https://hub.mender.io/u/mirzak)
#### Post date: [October 30, 2019, 8:43am UTC](https://hub.mender.io/t/uart-stopped-working-after-update-from-thud-to-warrior/1201/3 "2019-10-30T08:43:21Z")
Also checkout the known issues section in this thread, [Raspberry Pi 3 Model B/B+](https://hub.mender.io/t/raspberry-pi-3-model-b-b/57).
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### Author:  [@TimFroehlich](https://hub.mender.io/u/TimFroehlich)
#### Post date: [October 30, 2019, 6:46pm UTC](https://hub.mender.io/t/uart-stopped-working-after-update-from-thud-to-warrior/1201/4 "2019-10-30T18:46:11Z")
@mirzak Ok, yeah, that’ll explain it. Will need to decide what the best course of action will be.
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### Author:  [@TimFroehlich](https://hub.mender.io/u/TimFroehlich)
#### Post date: [October 30, 2019, 6:59pm UTC](https://hub.mender.io/t/uart-stopped-working-after-update-from-thud-to-warrior/1201/5 "2019-10-30T18:59:23Z")
Also, I did confirm that the mender update itself didn’t cause any problems. For myself I’m going to set the Linux version back to the version that the Raspberry Pi used in Thud and see if I get the old dtb and the serial port survives the update
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### Author:  [@TimFroehlich](https://hub.mender.io/u/TimFroehlich)
#### Post date: [October 30, 2019, 11:38pm UTC](https://hub.mender.io/t/uart-stopped-working-after-update-from-thud-to-warrior/1201/6 "2019-10-30T23:38:50Z")
Ok, looks like setting my Linux version back to 4.14 solved the uart issue and will likely have fixed any other dtb-related issues I might have run into later.
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### Author:  [@mirzak](https://hub.mender.io/u/mirzak)
#### Post date: [October 31, 2019, 4:56pm UTC](https://hub.mender.io/t/uart-stopped-working-after-update-from-thud-to-warrior/1201/7 "2019-10-31T16:56:11Z")
Thanks for reporting back.