code:
void setup()
{
pinMode(10, OUTPUT);
}
void loop()
{
analogWrite(10, 16);
}
I can't figure out why the LED flickering when I try to run this code. I am new to Arduino
Well, you haven't posted the code according to the instructions but it is so trivial in this case it probably does not matter.
You haven't specified what sort of LED it is, but R2 is clearly the wrong value - it should be 330 Ohms, not 32.
what type of board?
what voltage are you running at?
how fast is the flicker?
If you're using a board with a low clock speed, then give it a low voltage which will cause the clock to run even slower, then you can start to see flickering from PWM since the frequency drops so low, especially when you're using such a low PWM value to begin with.
If you increase the PWM value to say 200, does the problem persist?
Try this code
void setup()
{
pinMode(10, OUTPUT);
analogWrite(10, 16);
}
void loop()
{
}
You are writing the same value too often, the reset when doing a new write might cause flickering.
And fix that resistor.
silly_cone:
what type of board?
what voltage are you running at?
how fast is the flicker?If you're using a board with a low clock speed, then give it a low voltage which will cause the clock to run even slower, then you can start to see flickering from PWM since the frequency drops so low, especially when you're using such a low PWM value to begin with.
If you increase the PWM value to say 200, does the problem persist?
I change resistor to 250 and change PWN value to 200 still flicker.
I am sorry, but "silly_cone"s suggestion was essentially nonsense. You are not going to cause the clock speed to be so slow as to see flicker, assuming you can even change the clock speed, and it is not (significantly) voltage dependent.
Grumpy_Mike has given you the correct answer (silly me - I missed it!) Use the corrected code he posted.
The flickering you are seeing is because the PWM is being unnecessarily rewritten very fast - as fast as it can be done in fact - as it is doing nothing else. A proper program only ever writes a new analog value when you need it to change.
Paul, try using PWM at low values on an Attiny85 at 128 kHz clock speed running at 2.8 - 3.0V. YES, you will see visible flicker, depending on how one defines "flicker." The way I define it, under the conditions I described, you absolutely will see it. The OP didn't tell us squat about their setup, so these aren't totally outlandish questions.
Well I agree it is the case that he hasn't deigned to actually answer our questions and reveal what he is doing and has only offered a diagram from a simulator which is clearly useless other than to describe his circuit. 
I should be surprised if a simulator detected overloading of the power supply and it would be unbelievably foolish to complain that a simulator was "flickering", so I think I am reasonably confident that he is actually using a UNO or fake UNO and not an Attiny85.
In any case, an Attiny85 is no place for "I am new to Arduino".
(I do hope the simulator junky here does not chime in now!)
I try ro change R2 to 330Ohm, and change PWM value to 127. But I still see LED (D2) flicker.
One thing I notice that when I am using Proteus that the when animating, the clock (Next to the label Animating in Proteus) seem to run slower the real time. So I guess the flicker only occur when using a simulator
P/s: I using step debug (I don't know what it's call but there is a ||> Icon) and I realize that the interval of the flicker is 50ms
Oh, you are using a simulator. So this whole "problem" is entirely meaningless. 
Perhaps we should have a separate forum for problems that are not real. 
Paul__B:
(I do hope the simulator junky here does not chime in now!)
Well given that I hope he does. 
@MinhQuan - simulators do not work very well, this is what you are seeing.
Paul, I completely missed those simulator diagrams. My bad. You're correct, in light of that, my suggestions were quite irrelevant.
Grumpy_Mike:
Well given that I hope he does.
He is lying low.