https://devzone.nordicsemi.com/f/nordic-q-a/61253/how-to-emulate-synchronize-uart-communication-with-libuarteI&#39;m working on a simple project based on the USB CDC ACM and libuarte example, the chip is nrf52840. A function is redirect the USB VCP data to another MCU via UART, just like what FTDI&#39;s FT232RL do. When a large packet (6k bytes+) comes from USBen-USTelligent Community 13Tue, 12 May 2020 13:54:30 GMThttps://devzone.nordicsemi.com/thread/249509?ContentTypeID=1Tue, 12 May 2020 13:54:30 GMT137ad170-7792-4731-bb38-c0d22fbe4515:6334f949-3378-4eeb-8fa4-1fbb09da74bfesonhon<p>Thanks.&nbsp;</p> <p>Actually, I blocked the&nbsp;APP_USBD_CDC_ACM_USER_EVT_RX_DONE event handler by hard delay, it works but looks not so good. Want to find a way to wait UARTE dealing with all bytes smoothly, such as SYNC uart transfer.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/249508?ContentTypeID=1Tue, 12 May 2020 13:47:45 GMT137ad170-7792-4731-bb38-c0d22fbe4515:feb4ada8-1ac1-4c0b-a25c-23cf82e726c7Kenneth<p>I think you should look into change the implementation such that you don&#39;t call&nbsp;app_usbd_cdc_acm_read() unless you know that the&nbsp;queue can handle the size (e.g. use nrf_queue_available_get()) of the data received by&nbsp;<span>app_usbd_cdc_acm_read(). I believe not calling&nbsp;app_usbd_cdc_acm_read() will stall the communication on USB, which should not be a problem, it should just cause a delay until queue is ready to receive more data. So the do{}while() should not run more times than&nbsp;</span>nrf_queue_available_get() says it can handle.</p> <p><span>Kenneth</span></p><div style="clear:both;"></div>