Hello: ①, to this problem, first check the 3.3V voltage formation circuit components, such as: To the 3.3V LM1117 low-voltage difference three-terminal voltage regulator chip input voltage is normal and stable, after checking the input is normal, then check whether the several filter capacitors of the LM1117 are normal, if normal, it may be the internal circuit of the chip is abnormal or damaged, and so on.