IOT2050 only boots with the UART cable enable.

[makaronke]

Hello,

I have an IOT2050 Advanced 6ES7647-0BA00-1YA2 FS9 with the V1.3.1 FW. I have an image of the OS on the SD card and I set it as number one in the boot_targets, but the booting sequence is only completing itself when I'm connected to the device with the UART cable. The same thing happens when the eMMC is the number one priority in the boot targets. When the cable is off, the device is starting ok, but after 6-7 seconds the STAT led is RED and when connecting myself to the device with UART cable again, I have IOT2050 blinking in the putty window. After simply typing “boot” command, the device is a booting and running normally afterwards.

So basically, when the UART cable is not connected, the boot sequence for some reason is stopping/not completing itself. I can't track down the logs of the unsuccessful bootings, because when the cable is connected, I don't have any issues. There is no visual representation when connected to the display port as well.

Any ideas what can be wrong with the Uboot/Kernel settings? Could the update to the FW V1.4.1 solve the issue?

Attaching a log file of the successful boot.

Thank you in advance.

IOT2050_boot_log_succeseful.txt

[jan-kiszka]

You seem to pick up noise on the unconnected UART that is interpreted by U-Boot as a key input, terminating the auto-boot. Recent firmware requires to hit "space" for that which is most likely resolving this issue. So, try a firmware update.

[makaronke]

Hello!
Thanks for the quick reply!

Following your suggestion, first I updated the FW to the V 1.4.1, tried to boot without UART cable and the result was the same. I've updated to the V 1.5.1, the latest available on the web-site, but still no result - the boot sequence just stops for some reason when UART cable is not connected.

Do you have any other suggestion?

[jan-kiszka]

Can you confirm that the latest firmware asks you for pressing space to enter the U-Boot console and that, if you your are stuck with that version and you plug the UART afterwards, you are inside the console already (hit enter, and you should get the prompt again)?

[makaronke]

Hi!
I can confirm both. When plugged with the UART cable, during boot sequence I'm asked to press SPACE to stop the autoboot (on the pic, I did press the space, but it'll go on with the booting without any issue)

When there is no UART connection, it fails to boot and when I'm connecting myself again via serial, after pressing enter, Isee promt again.

[makaronke]

Do you think that eliminating the boot delay (from 2s to 0s) can somehow solve the issue? The application I'll be using the IOT2050 for, will be a fully autonomous installation with possible power shortages, so the autobooting is required.

[jan-kiszka]

Very strange result. Ok, what happens if you do not connect the RX line of the UART, only Ground and TX? Do you get an output from a failing boot? Or does it work then?

Another hardware experiment: If you bridge RX and Ground, does it work then?

Yes, a custom-built firmware can likely mitigate the issue, but as that takes you off the supported path and it would be good to understand more about the root cause, I would suggest trying to above first.

[makaronke]

Taking out the the RX pin from the connection leads to the regular bootup of the PC, no issues.
Shorting GND and RX pins leads to the regular boot, no issues.

[jan-kiszka]

So we most likely have an EMC issue here. Would that RX shorting by a viable workaround for you?

@huaqianli, @BaochengSu, seems that SPACE is not enough in some cases...

[makaronke]

I believe this shorting will be a comfortable solution, thanks a lot for the support!
I had another IOT2050 for the same project, but no such issue was detected, the unit works just fine.

Cheers!

[BaochengSu]

So we most likely have an EMC issue here. Would that RX shorting by a viable workaround for you?

@huaqianli, @BaochengSu, seems that SPACE is not enough in some cases...

Maybe modeling the autoboot stop to configurable via something such as CONFIG_AUTOBOOT_STOPPER:

• "" stands for any
• "[[:ascii:]]" stands for an ascii string. For example, SPACE == " ", IOT2050 == "IOT2050" , etc.