https://devzone.nordicsemi.com/f/nordic-q-a/83762/uart-api-types-and-useI had a look on APIs to use UART in Zephyr in the link https://docs.zephyrproject.org/latest/reference/peripherals/uart.html#uart-interrupt-api . There are three types: Poll, Interrupt and Asynchronous using DMA. 1. In what situation which mode is prefrerden-USTelligent Community 13Tue, 18 Jan 2022 14:25:20 GMThttps://devzone.nordicsemi.com/thread/348319?ContentTypeID=1Tue, 18 Jan 2022 14:25:20 GMT137ad170-7792-4731-bb38-c0d22fbe4515:741035a4-a901-41df-8af4-9a8855b4cd24Amanda Hsieh<p>Hi,&nbsp;</p> [quote user=""]1. In what situation which mode is prefrerd.[/quote] <p>It depends on what benefit you want. See the explanation in this <a href="https://devzone.nordicsemi.com/f/nordic-q-a/78244/uart-i2c-twi-communication-with-polling-interrupt-dma-method-different-brief-explained-guide">post</a>.&nbsp;</p> <p></p> [quote user=""]2. May, some one give an example of each?[/quote] <p><span>&nbsp;Poll (default):&nbsp;</span><a href="http://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.8.0/nrf/samples/peripheral/lpuart/README.html">Low Power UART</a>&nbsp;</p> <p><span>Interrupt-based UART: <a href="https://devzone.nordicsemi.com/guides/nrf-connect-sdk-guides/b/getting-started/posts/nus-on-ncs-the-nordic-uart-service-with-the-nrf-connect-sdk">NUS on NCS: The Nordic UART Service with the nRF Connect SDK</a>&nbsp;and&nbsp;<a href="http://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.8.0/nrf/samples/bluetooth/hci_lpuart/README.html">HCI low power UART</a></span></p> <p><span>Asynchronous using DMA:&nbsp;</span><a href="http://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.8.0/nrf/samples/bluetooth/peripheral_uart/README.html">Bluetooth: Peripheral UART</a></p> <p></p> [quote user=""]3. Is it mondatory to use Semphore in Asynchronous mode ?&nbsp;[/quote] <p><span>No, Semaphore is not used in&nbsp;<a href="http://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.8.0/nrf/samples/bluetooth/peripheral_uart/README.html">Bluetooth: Peripheral UART</a>&nbsp;sample.&nbsp;&nbsp;</span></p> <p><span></span></p> <p><span>Regards,<br />Amanda</span></p><div style="clear:both;"></div>