Weird output from serial port

[Ivan Popov]

Hello,

In short, my use case is that I'm trying to onboard a Thingy:91 to AWS IoT Core through the available code sample following this tutorial (and the related library description linked in it).

What I did successfully was: 

1. I managed to provision the certificates to the device (I can see them listed along with the default ones with the AT%CMNG=1 command).
2. I created a project from the sample (aws_iot), edited the required properties (AWS MQTT endpoint, device_id, topics, ...) and managed to build it in VSCode for the thingy91_nrf9160_ns target.
3. I flashed the resulting app_signed.hex file on the device with the Programmer application (it took ~50 seconds).

However, on rebooting the device in regular mode I get nothing in AWS IoT Core - nothing in the topics, nothing for the shadow.

I tried to get some clues from the serial terminal but all I get is a blank, black terminal. (Interestingly executing commands in the LTE Link Monitor is successful ...)

I tried to play a bit with the ports and their options but the only visible result was on the second (not the default for any of the previously (successfully) executed operations) port and it looked like the wrong Baud Rats was given:

Any ideas on how to proceed and how to determine what might be wrong? I've followed the tutorials as closely as possible, yet we're here.

Best regards,

Ivan Popov

[Håkon Alseth]

Hi Ivan,

 

Ivan Popov said:

... and since the problem is already different from the one in the title of the ticket, I'm not very sure if I have to close this and open another one, or we just can finish this here?

No worries, let's continue here.

Ivan Popov said:

As for the brltty problem - I've had it before with another device (as you can see from my answer here), and I've removed it some time ago.

Glad to hear that you got that one sorted out.

This was something I had completely forgotten about myself, until I recently got a new computer at work; and then ran into it again.

 

Ivan Popov said:

And here is output in the Serial Terminal (from the file) (the aws_iot sample is flashed on the device):

Still no visible output on ttyACM0? Same thing with other serial consoles, like putty/minicom etc? Could you uncheck the hardware flow control, to ensure it is off?

Ivan Popov said:

device is visible in AWS, so I assume the sample works and the communication can be maintained through MQTT;

This is good.

 

Ivan Popov said:

the build for the sample fails with the only change to it being the addition of the AWS properties in the respective overlay file (overlay-aws.conf) and the error is addressed in this ticket too:

This has references to subimage "b0" - do you have CONFIG_SECURE_BOOT=y set in your current configuration? Thingy91 is applying a pm_static.yml file, as it expects a certain layout in order for the bootloader over serial to work, which does not include the b0 immutable bootloader, which is automatically attached as a sub-image when setting CONFIG_SECURE_BOOT=y.

Here's the default pm_static it applies for each project:

https://github.com/nrfconnect/sdk-nrf/blob/main/boards/arm/thingy91_nrf9160/thingy91_pm_static.yml

 

When b0 is added, which is a first-stage bootloader for mcuboot, you will not be able to fit the image onto the flash, as it conflicts with what is statically defined in the above file.

 

Kind regards,

Håkon