https://devzone.nordicsemi.com/f/nordic-q-a/98117/ncs-2-3-0-usb-cdc-acm-uart-is-there-a-way-to-get-a-callback-on-dtr-changesThe samples/subsys/usb/cdc_acm sample polls for DTR to be set then sets DCD and DSR before data can be received. On macOS sending data to the CDC ACM tty will block until this sequence is completed. In an application where the device may be pluggeden-USTelligent Community 13Mon, 27 Mar 2023 13:40:24 GMThttps://devzone.nordicsemi.com/thread/417700?ContentTypeID=1Mon, 27 Mar 2023 13:40:24 GMT137ad170-7792-4731-bb38-c0d22fbe4515:2b22efcc-36bc-45c6-a14d-5b1d92a28b71Kenneth<p>Hi,</p> <p>I can only find (as you) that you need to manually call for intance the status by&nbsp;<span>uart_line_ctrl_get</span><span>(</span><span>dev</span><span>, </span><span>UART_LINE_CTRL_DTR</span><span>, &amp;</span><span>dtr</span><span>). </span></p> <p><span>I can see that there is a callbak in cdc_acm.c where the&nbsp;</span>cdc_acm_class_handle_req() handle the&nbsp;SET_CONTROL_LINE_STATE, but unfortunately I can&#39;t find any way to forward that other than to modify the cdc_acm class.</p> <p>Kenneth</p><div style="clear:both;"></div>