https://devzone.nordicsemi.com/f/nordic-q-a/68154/usb-cdc-acm-flow-controlIn our current implementation of the CDC ACM output, we use a blocking wait for the APP_USBD_CDC_ACM_USER_EVT_TX_DONE after writing to the cdc acm stack. We are using Teraterm to receive and print the data on the PC. We noticed that in particular whenen-USTelligent Community 13Tue, 10 Nov 2020 10:35:17 GMThttps://devzone.nordicsemi.com/thread/279183?ContentTypeID=1Tue, 10 Nov 2020 10:35:17 GMT137ad170-7792-4731-bb38-c0d22fbe4515:9eae716e-2d37-4363-95ce-165170998f07Kenneth<p>In principle this should work, you could query&nbsp;app_usbd_cdc_acm_line_state_get for RTS signal, however I have not tested if this actually will work as expected, but I guess you could try. Alternatively you could just use some handshaking on the application layer, e.g.&nbsp;send for instance 1kB and then wait for a command before sending the next 1kB. The command can also contain information about how much data have been received (e.g. and offset) in case data is lost/missed etc.</p> <p>Best regards,<br />Kenneth</p><div style="clear:both;"></div>