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

[Mike]

Duh! I think it's being caused by "power only" USB cables! I was using two, one for each USB port. Tried the one from the "nRF USB" port on a ESP32 board and it wouldn't show up on the USB bus. While trying to fix the CP2104 driver, I ran across someone mentioning these "power only" USB cables. Tried a different USB cable and my ESP32 shows up. Used that cable on the nRF52840 PDK with the usbd_cdc_acm example and I get "Hello USB CDC FA demo: 658"!!

I'll verify the other two boards in the morning. But I'm pretty sure they're having the same issue.

Then after trying the USB enumeration calibration app on the PDK, I'll clean up and close the MyPage support ticket.

Sorry for all of the extra trouble!