[Bug] Booting SD-Card on EV3 if detected does not work

[cvoinf]

Describe the bug
What is the problem?
If a sd-card is mounted on an EV3, neither pybricks nor the image on the sd-card is booting. The EV3 just starts booting repeatedly without Error-Message.

To reproduce
Steps to reproduce the behavior:

1. Insert a sd-card with a bootable image, e.g. ev3dev
2. Start the EV3 with pybricks previously flashed

Expected behavior
If the original fimware from Lego is flashed on the EV3, the sd-card is booting if inserted, as expected. If pybricks is flashed on the EV3, it should behave similarly, but the EV3 is stuck in a boot-loop

Screenshots
Only the start-screen reappears endlessly.

[BertLindeman]

Hello,

Have inserted my EV3 sd card into the EV3 that has the Pybricks V4 beta firmware and reboots like ev3dev:

Some thoughts:

• sd-card inserted completely
• sd-card correct data (must be if it does boot on a LEGO firmware)
• not a defect sd-card?

According to me the firmware installed has nothing to do with the program running from the sd-card.
It is a completely different boot system.

Makes me very happy again to see how fast pybricks V4 boots on an EV3.

[cvoinf]

Mh, I checked it again and I still have the same behaviour. The SD-Card is inserted completely, it boots if the original firmware is on the EV3, but doesn't if pybricks 4.0.0b8 is installed.

It is not a problem for me now, but when I installed pybricks the first time I unintentionally left the SD-Card inside, which resulted in the described boot loop. I first thought, pybricks was corrupt, until I recognized the SD-Card.

I don't know if it is important, but on my SD-Card a special version of ev3dev is installed: Yocto ev3dev with ROS support:
https://hacks4ros.github.io/h4r_ev3_ctrl/index.html

I haven't tried other images yet.

[dlech]

It looks like the hacks4ros image uses a boot.src instead of uEnv.txt like the current ev3dev releases. So that might have something to do with it.

It looks like the current boot command should still load it though since it runs loadbootscr.

https://github.com/pybricks/u-boot/blob/76ac2d9bff2ad90aa0e86d4750f0459ca9dd7e47/configs/legoev3_defconfig#L25

I don't suppose you have a way to look at the serial output on sensor port 1 to debug it?

[BertLindeman]

I don't suppose you have a way to look at the serial output on sensor port 1 to debug it?

Yes I can 😃 David.

All I did was unpack the two tar files to fat16 and ext4 partitions.
(Unpack instructions for the FAT16 partition is incorrect. File is no bz2 but gz.)
SD-card in EV3
Thighy in port 1

Terminal log, many times of this:

ÿEV3 initialization passed!
Booting EV3 EEprom Boot Loader

        EEprom Version:   0.60
        EV3 Flashtype:    N25Q128A13B

EV3 Booting system

Jumping to entry point at: 0xC1080000


U-Boot 2025.07-rc5-pybricks-2.0.1+ (Jul 06 2025 - 18:42:58 +0000)

DRAM:  64 MiB
Core:  10 devices, 10 uclasses, devicetree: separate
MMC:   da830-mmc: 0
Loading Environment from nowhere... OK
In:    serial@10c000
Out:   serial@10c000
Err:   serial@10c000
Autoboot in 0 seconds - press 'l' to stop...
194 bytes read in 3 ms (62.5 KiB/s)
## Executing script at c0600000
2753504 bytes read in 439 ms (6 MiB/s)
## Booting kernel from Legacy Image at c0007fc0 ...
   Image Name:   Linux-3.16.7-ckt14-7-rc1-ev3dev-
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    2753440 Bytes = 2.6 MiB
   Load Address: c0008000
   Entry Point:  c0008000
Working FDT set to 0
   XIP Kernel Image to c0008000
FDT and ATAGS support not compiled in

EV3 initialization passed!
Booting EV3 EEprom Boot Loader

        EEprom Version:   0.60
        EV3 Flashtype:    N25Q128A13B

EV3 Booting system

Jumping to entry point at: 0xC1080000


U-Boot 2025.07-rc5-pybricks-2.0.1+ (Jul 06 2025 - 18:42:58 +0000)

DRAM:  64 MiB
Core:  10 devices, 10 uclasses, devicetree: separate
MMC:   da830-mmc: 0
Loading Environment from nowhere... OK
In:    serial@10c000
Out:   serial@10c000
Err:   serial@10c000
Autoboot in 0 seconds - press 'l' to stop...
194 bytes read in 4 ms (46.9 KiB/s)
## Executing script at c0600000
2753504 bytes read in 439 ms (6 MiB/s)
## Booting kernel from Legacy Image at c0007fc0 ...
   Image Name:   Linux-3.16.7-ckt14-7-rc1-ev3dev-
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    2753440 Bytes = 2.6 MiB
   Load Address: c0008000
   Entry Point:  c0008000
Working FDT set to 0
   XIP Kernel Image to c0008000
FDT and ATAGS support not compiled in

[dlech]

Thanks Bert!

It looks like it is reading the boot.scr and the uImage correctly. But then U-Boot panics and reboots because we don't have devicetree or ATAG support enabled.

I'm guessing that this kernel image has the devicetree embedded, so we probably just need to enable ATAGs.

That's a super-old kernel though! It's from 2014, which was the very early days of ev3dev!

[BertLindeman]

My latest /etc/motd of ev3dev:

Generated by /home/bert/bin/update-motd.sh
            _____     _
  _____   _|___ /  __| | _____   __
 / _ \ \ / / |_ \ / _` |/ _ \ \ / /
|  __/\ V / ___) | (_| |  __/\ V /
 \___| \_/ |____/ \__,_|\___| \_/


Welcome to ev3-micropython-v2.0.0-sd-card-image
        Kernel:         4.14.117-ev3dev-2.3.5-ev3 armv5tejl (GNU/Linux)
        Debian version: 9.13 - Debian 9 Stretch
        EV3DEV image:   ev3-micropython-v2.0.0-sd-card-image