usbd_cdc_acm examples bricks nrf52840 PDK

[Mike]

I've got a new nrf52840 PDK. I got Eclipse, JLink, and the nrf command line tools to work today. I've been able to run the precompiled examples (blinky, led_softblink), compile and run both of them, and step thru blinky using Eclipse a source line at a time. All good!

Then I tried the usbd_cdc_acm example by copying the copying the _pca10056.hex file to the JLink mount point. The eval board reset and then nothing! It no longer shows up as a MSD drive nor as a USB device at all! Power cycling and resetting the board does nothing.

If I hold down the IF BOOT/RESET button and then apply power, the board appears to go into "bootloader" mode. The IF LED is blinking, Windows thinks it's a MBED USB drive, there's an empty bootloader.htm file on it. But the bootloader quickly (30 seconds) gets some kind of error and Windows unmounts the drive, and complains about an unknown error.

I've seen in other postings on the DevZone that when it's in "bootloader" mode, I should drag and drop the offical Nordic firmware image for my board. Unfortunately, I can't find any such firmware image. I can find the nrf52832's MBED and JLink images, but I'm not brave enough (yet!) to try it on the nrf52840.

Any ideas on what I did wrong with the usbd_cdc_acm example? And more importantly, how I might rescue my board?

Thanks,

Mike

[Sigurd]

Hi,

First make sure that all board switches are in the correct position. I.e. the nRF power source is set to VDD, and that the nRF only switch is set to “default”. Then plug the USB cable into the USB IF MCU connector, as shown in this picture.

You need to reprogram the JLINK firmware to the Segger J-Link chip, only if the J-Link drive does not appear as a mounting point. You can download the latest On-Board J-Link firmware here. The latest firmware right now is version 170724. Simply drag and drop the file J-Link OB-SAM3U128-V2-NordicSemi 170724.bin into the bootloader mounting point.

[Mike]

That works if I mount the PDK on a Linux machine. Windows 10 gets a USB error too quickly so I wasn't able to copy the bin file to the bootloader before the mount point would go away.

Thanks for the link. I would have sworn I looked there for the firmware but it must have been staring me in the face.

Now to try the usbd_cdc_acm example again to see if it happens again.

[Sigurd]

Great, let me know how it goes. What revision of the nRF52840-PDK are you using? V0.9.1?

[Mike]

It's a v0.9.2!

As far as I can determine, the usbd_cdc_acm demo doesn't do anything. Although I can reflash it now! :-)

For the USB demo, I would expect the "nRF USB" connector to be used. But nothing shows up on that USB connector (using 'lsusb' to check). So I must be doing something wrong.

Are there any instructions for running the USB examples?

[Sigurd]

You can find the instructions on how to run the example here.

Does the device show up in your computer's device manager ? Do you have issues with the other USB examples also? Could you try e.g. the usbd_hid_generic example?