Arduino for STM32

Dear All, plz guide me. i am using stm32f401cc black pill, but adc ouput is noisy it fluctuate a lot even on dc input in serial plotter, my entire project is based on ADC OUTPUT ,so plz guide me how i can remove noise ...Thanks

place an RC filter before the pin and preferably use an op amp as a buffer before the pin.
otherwise you can try average the readings

hiii sir thanks for reply.. my adc input signal is in millivolts if i put any filter then input signal will also get suppressed, by project is to sense overcurrent , so i used current sensor CT(current transformer) & output of ct are in millivolt. i cannot average the sample because my processing is of real time signal.. plz guide if u have any idea ..thanks

for small signals, use an op amp to amplify it. the noise is most likely radio waves, so check if you have long wires (e.g. > 10 cm) to your sensor etc.
those works as antennas and stm32 adc is sensitive to pick up radio waves from the air with an antenna.
you would need to reduce that radio waves being picked up, e.g. use short wires and shielding (e.g. place in a metal box) if possible, that may help.
In addition, pace a large capacitor between VDD (3.3v) to GND or use batteries - using batteries prevent ac signal noise.