https://devzone.nordicsemi.com/f/nordic-q-a/29930/usb-cdc-acm-flushing-write-dataHi! I have tried to use USB CDC ACM in my project but after running the USB CDC ACM example in the SDK, I found out that the example have the issue of not sending the data out completely. It requires multiple calls to the app_usbd_cdc_acm_write functionen-USTelligent Community 13Mon, 29 Jan 2018 11:57:48 GMThttps://devzone.nordicsemi.com/thread/119034?ContentTypeID=1Mon, 29 Jan 2018 11:57:48 GMT137ad170-7792-4731-bb38-c0d22fbe4515:07de64e9-e7f0-4662-9256-49ca6fb0a656J&#248;rgen Holmefjord<p>Which SDK version are you using? Could you post the code you used after you changed the buffer size?</p><div style="clear:both;"></div>