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Serial Output for the Thingy:91 With Custom Firmware

Hello,

I am currently tweaking the Thingy:91 to run a stripped down version of my custom application. I have been able to flash the device with the Thingy:91's sample at_client and asset_tracker applications that are floating about the DevZone. They both flash and I can see the output of the asset_tracker application on the Link Monitor program.

The board version is PCA20035 v1.0.0 with the dts set to nrf9160_pca20035_v0_3_0 (as it's the latest revision available in SDK v1.0.0).

When I flash the custom firmware, the device seems to run as expected. I can see the RGB LED change colour during the different states of the application but the serial output is blank. Is there something else that is needed in the set-up for the pca20035 that allows the serial port to work for the Link Monitor? Possibly something similar to how the nRF52840 on the PCA10090 can be set with CONFIG_BOARD_PCA10090_UART0_ARDUINO=y to run the messages over UART pins instead of the USB?

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  • No, I would like it to function as a UART-USB bridge. The issue is that for my custom firmware, the device doesn't print to the link monitor. The device does print to the link monitor when it uses the pre-compiled Thingy:91 asset_tracker.

    There must be something different between the custom firmware and the pre-compiled asset_tracker that allows the UART-USB output to show in the Link Monitor but not in the custom firmware.

  • Does any of the other samples, like mqtt_simple, output anything on the UART when configured with BOARD=nrf9160_pca20035?

    Can you share more info about your custom firmware, like the prj.conf and possible .overlay's that are applied?

     

    Kind regards,

    Håkon

  • Hi Håkon,

    Unfortunately none of the sample applications built for the nrf9160_pca20035_v0_3_0ns device print information to the Link Monitor. When I run the Thingy:91 pre-compiled Asset Tracker application, I can see this from the Link Monitor:

    The application is pretty simple and is a stripped down version of the main application I am building. Effectively this version will just alternate between GPS and NB-IoT every 2 minutes. It will launch into GPS when booted, acquire a fix, store it and after 2 minutes switch to LTE and send that fix by UDP.

    I can tell that the application is working as I set the Blue LED to flash during GPS and then Green when in LTE. The device is clearly swapping between the two happily. The only issue is that the 'prink()'s are not displaying down the COM port.

    The prj.conf:

    The last two blocks of config options are taken from the pca20035_v0_3_0 asset tracker prj.conf

    The overlay (nrf9160_pca20035_v0_3_0ns.overlay):

    This is copied into SPM as a non-secured overlay version as well.

  • Looking more closely at each DTS file, it would appear that the basic pca20035.dts uses the v0.3.0 board layout anyway (#including them). I reconfigured the overlay for pca20035 for both secure and non-secure and the COM port is not spitting out my application printk()s.