10 replies to this topic

[andrewq2]

I just got my netduino and I'm starting to try to get analog input and I always get 0 when I read my pin(A0). Do you see anything I did wrong?

My setup looks like this

3.3->AREF

A0->Photo Resistor->GND

public class Program
    {
        public static void Main()
        {
            // write your code here
            InterruptPort tester = new InterruptPort(Pins.GPIO_PIN_A0, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeBoth);
            tester.Dispose();

            AnalogInput apin0 = new AnalogInput(Pins.GPIO_PIN_A0);
            apin0.SetRange(0, 100);

            int test = 0;
            while (true)
            {
                Thread.Sleep(250);
                test = apin0.Read();
                Debug.Print("Test: " + test);
            }

        }

    }

[klotz]

I just got my netduino and I'm starting to try to get analog input and I always get 0 when I read my pin(A0). Do you see anything I did wrong?

My setup looks like this

3.3->AREF

A0->Photo Resistor->GND

public class Program
    {
        public static void Main()
        {
            // write your code here
            InterruptPort tester = new InterruptPort(Pins.GPIO_PIN_A0, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeBoth);
            tester.Dispose();

            AnalogInput apin0 = new AnalogInput(Pins.GPIO_PIN_A0);
            apin0.SetRange(0, 100);

            int test = 0;
            while (true)
            {
                Thread.Sleep(250);
                test = apin0.Read();
                Debug.Print("Test: " + test);
            }

        }

    }

You would need another resister to 3.3Vdc to develop a voltage divider. There is no pull-up in the An-in.

[andrewq2]

You would need another resister to 3.3Vdc to develop a voltage divider. There is no pull-up in the An-in.

I'm confused would it look like
AREF+3.3v->resistor(what resistance?)->ground?->photo resistor->A0?

[klotz]

I'm confused would it look like
AREF+3.3v->resistor(what resistance?)->ground?->photo resistor->A0?

First you need to know what the resistance of the photo resister is. Mine was 25k full dark.
Second you need to decide if you want it to pull-up or pull-down. I used mine in a pull-up.
Then choose a resitance to give you some kind of reasonable current limit, I chose 10K since I just wanted to play.
So using the attached schematic, I put the photoresister in a R1, a 10k in R2, you can try it either way and pick the one you like.

Attached Files

•  voltage divider.png   1.62KB   61 downloads

[andrewq2]

Thank you for explaining now i understand. Time to play with my netduino!

[klotz]

Thank you for explaining now i understand. Time to play with my netduino!

The fun is just begining
The next thing you want to do is check out the projects page.

[ajcg1973]

So using the attached schematic...

klotz, what software are you using to generate the schematic? Thanks.---AJB

[CW2]

klotz, what software are you using to generate the schematic?

My guess: CadSoft Eagle (?)

[klotz]

My guess: CadSoft Eagle (?)

Yep, I use Cadsoft Eagle. But don't ask me for help with it. I am just returning to doing hardware after 40 years and am trying to catch up.I just kindof hack away with Eagle until something works.

[EC_dude]

Hi I might sound very dumb here but how do you people come to know of those commands ? I found this thread when i searched for analog input syntax. Is there some documentation or anything which can help me getting familiar with such commands ? PS: I'm a beginner at Visual C# and micro framework.

[Chris Walker]

Hi EC_Dude, For everything other than AnalogInput and PWM, the online Microsoft .NET MF reference is probably the best resource. For AnalogInput and PWM, the forums are the best resource for now...but we're also working on adding them to the "getting started" guide and adding "how-to's" to the projects page. Chris