Checking USB connection state using cdc_acm with nRF52840 outside of the USB library

[andrewhamill]

Hi guys,

I'm writing firmware for the nRF52840 using Zephyr, based on the cdc_acm example, using zephyr,cdc-acm-uart. I'm trying to blast out a ton of data, and need to capture elsewhere in the application when the USB connection goes to the "Device suspended" or "Device disconnected" states, to cancel the data transfer. Does anybody know how to check for the USB connection state from outside of the USB driver, specifically to see if it is still connected please?

Using nrfconnect v2.1.0

Thanks!

Andrew

[Håkon Alseth]

Hi,

 

These are local to the CDC_ACM implementation:

https://github.com/nrfconnect/sdk-zephyr/blob/v3.1.99-ncs1-1/subsys/usb/device/class/cdc_acm.c#L119-L123

And the "USB state" is handled in this callback:

https://github.com/nrfconnect/sdk-zephyr/blob/v3.1.99-ncs1-1/subsys/usb/device/class/cdc_acm.c#L341

 

If you also want the main application to get notified with the usb state (ie. configured, reset, suspend, etc), you can provide a callback to the usb_enable() function:

https://github.com/nrfconnect/sdk-zephyr/blob/v3.1.99-ncs1-1/samples/subsys/usb/cdc_acm/src/main.c#L92

Here's an implementation of the status_cb:

https://github.com/nrfconnect/sdk-zephyr/blob/v3.1.99-ncs1-1/samples/subsys/usb/hid/src/main.c#L117-L135

 

Kind regards,

Håkon