1. First, open the Xiaomi sports client corresponding to mi band, and click the connected mi band 4. As shown in the figure.
2. Slide the page, find "Heart Rate Detection" at the bottom, and then click Open.
3. You can see that the current status is displayed as closed. Click the first item, Select Mode.
4. Select the automatic heart rate+assisted sleep detection mode here, and then click Select.
5. Finally, select OK in the pop-up dialog box to complete the setting of heart rate detection.