usbd_cdc_acm example recognized by PC but cdc_acm_user_ev_handler never called

[GJSea]

From the latest Nordic SDK 15.2, I'm running the usbd_cdc_acm example on an NRF52840 connected to a PC using USB. The firmware correctly executes the USBD_POWER_DETECTION code path, usbd_user_ev_handler events notify correctly and the PC lists the device's COM port in device manager. Nice!

My simple PC program that opens a serial port and writes characters down the wire works fine over any Arduino device, is able to connect to the 52840 COM port listed in device manager, even the writes are successful, however the firmware never receives events of any kind in the cdc_acm_user_ev_handler callback, no connection event, not RX events, nothing.

Any ideas? Thanks!

[Jørgen Holmefjord]

Hi,

Are you testing this with the example from the SDK, or did you modify it in any way? 

Did you test it on nRF52840 DK, or on a custom board?

Best regards,
Jørgen

[Jørgen Holmefjord]

Have you tested this on a nRF52840 DK? I'm getting events in cdc_acm_user_ev_handler with Windows and Putty. 

[GJSea]

Hi... 

I eventually figured it out, the NRF52840 USB implementation requires DTR to be set in order to work, many terminal programs don't set this. I found the answer in this posting:

https://devzone.nordicsemi.com/f/nordic-q-a/28107/nrf52-dk---usb-cdc-acm-example-not-working-with-hterm-qt