https://devzone.nordicsemi.com/f/nordic-q-a/128957/uart-hardware-flow-controlHello Nordic community, using nrf5-sdk for nrf52840 SoC, I followed the uart example as below. The uart tx and rx works fine BUT NOT THE HWFC eg. When the CTS is set HIGH, the transmitter (nRF52840) doesn&#39;t stop sending. (I tried setting theen-USTelligent Community 13Fri, 14 Aug 2026 11:19:40 GMThttps://devzone.nordicsemi.com/thread/570261?ContentTypeID=1Fri, 14 Aug 2026 11:19:40 GMT137ad170-7792-4731-bb38-c0d22fbe4515:4bae307f-fca7-4147-a252-5cf0df66dea2Ressa<p>Hi,<br /><br />Are testing it on nRF52840 DK or custom board? If this is on nRF52840 DK using the default VCOM0 pins (P0.05 RTS / P0.06 TXD / P0.07 CTS / P0.08 RXD), the interface MCU on the DK actively drives CTS as part of its &quot;Dynamic HWFC&quot; auto-detection, and only releases the pin if it detects HWFC is not in use (or if SW11 is switched off). If you&#39;re trying to force CTS externally on those specific pins, you may be fighting the interface MCU rather than actually controlling the nRF52840 CTS input. Worth checking with a scope or logic analyzer what is really on that pin — not just what you are asserting.<br /><a href="https://docs.nordicsemi.com/r/bundle/ug_nrf52840_dk/page/ug/dk/dyn_hw_flow_control.html">Dynamic hardware flow control • nRF52840 DK Hardware • Technical Documentation<br /><br /></a>Also feel free to switch to nRF Connect SDK instead of nRF5 SDK. You can find a lot of guidance for new developments on nRF Connect SDK.<br /><br /><br />Best regards,<br />Ressa</p><div style="clear:both;"></div>