6 replies to this topic

[Jason Smith]

All,

I successfully got the Memsic 2125 Accelerometer to work on my Netduino, so I decided to take a crack at controlling a servo by measuring Tilt. I'm sure I could do a lot to make this more efficient but I just wanted to get this working first:

Below is the code I used (I plan on doing a lot more work to get this going right. Once I do, I will properly comment my code and clean things up to make it more user friendly.):

using System;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;

namespace Memsic
{
    public class Program
    {
        static int count = 0;
        static uint _lastposition = 0;
        static InputPort Xin = new InputPort(Pins.GPIO_PIN_D2, false, Port.ResistorMode.Disabled);
        static InputPort Yin = new InputPort(Pins.GPIO_PIN_D3, false, Port.ResistorMode.Disabled);
        static PWM ServoY = new PWM(Pins.GPIO_PIN_D9);
        public static void Main()
        {
            while (true)
            {
                int X = TiltToServoPulse(GhettoTilt(Xin));
                int Y = TiltToServoPulse(GhettoTilt(Yin));
                MoveServo(ServoY, (uint)Y);
                //Debug.Print("X:" + X + "," + "Y: " +  Y);
             }
        }

       //Read the specified port and grab some values to calculate Ghetto Tilt.
        static int GhettoTilt(InputPort axe)
        {
            count = 0;
            // Loop until pin reads a low 
            while (axe.Read() == true) { }
            // Loop until pin reads a high 
            while (axe.Read() == false) { }
            // Loop until pin reads a low and count
            while (axe.Read() == true)
            {
                if (axe.Read() == false) { break; }
                count += 1;
            }
            count = count - 21;
            return count;
        }

        static void MoveServo(PWM whatservo, uint whereto, int sleep = 0)
        {
            if (_lastposition == whereto) { return; }
            uint HowLong = 0;
            if (whereto > 2000 || whereto < 1000) { return; }
            whatservo.SetPulse(20000, whereto);
            if (_lastposition == 0) { HowLong = 300; }
            else { HowLong = _lastposition > whereto ? (_lastposition - whereto) / 3 : (whereto - _lastposition) / 3; }
            Debug.Print("" + HowLong);
            Thread.Sleep((int)HowLong);
            whatservo.SetPulse(0, whereto);
            _lastposition = whereto;
            if (sleep != 0) { Thread.Sleep(sleep); }
        }

        static int TiltToServoPulse(double Tilt)
        {
            double pulse = 0;
            Tilt = Tilt - 1;
            double calc1 = Tilt / 18;
            pulse = (calc1 * 1000) + 1000;
            return (int)pulse;
        }
    }
}

..and a video of the results:
http://www.youtube.com/watch?v=xTijhSgqMfM

Jason

[greg]

All,

I successfully got the Memsic 2125 Accelerometer to work on my Netduino, so I decided to take a crack at controlling a servo by measuring Tilt. I'm sure I could do a lot to make this more efficient but I just wanted to get this working first:

Below is the code I used (I plan on doing a lot more work to get this going right. Once I do, I will properly comment my code and clean things up to make it more user friendly.):

using System;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;

namespace Memsic
{
    public class Program
    {
        static int count = 0;
        static uint _lastposition = 0;
        static InputPort Xin = new InputPort(Pins.GPIO_PIN_D2, false, Port.ResistorMode.Disabled);
        static InputPort Yin = new InputPort(Pins.GPIO_PIN_D3, false, Port.ResistorMode.Disabled);
        static PWM ServoY = new PWM(Pins.GPIO_PIN_D9);
        public static void Main()
        {
            while (true)
            {
                int X = TiltToServoPulse(GhettoTilt(Xin));
                int Y = TiltToServoPulse(GhettoTilt(Yin));
                MoveServo(ServoY, (uint)Y);
                //Debug.Print("X:" + X + "," + "Y: " +  Y);
             }
        }

       //Read the specified port and grab some values to calculate Ghetto Tilt.
        static int GhettoTilt(InputPort axe)
        {
            count = 0;
            // Loop until pin reads a low 
            while (axe.Read() == true) { }
            // Loop until pin reads a high 
            while (axe.Read() == false) { }
            // Loop until pin reads a low and count
            while (axe.Read() == true)
            {
                if (axe.Read() == false) { break; }
                count += 1;
            }
            count = count - 21;
            return count;
        }

        static void MoveServo(PWM whatservo, uint whereto, int sleep = 0)
        {
            if (_lastposition == whereto) { return; }
            uint HowLong = 0;
            if (whereto > 2000 || whereto < 1000) { return; }
            whatservo.SetPulse(20000, whereto);
            if (_lastposition == 0) { HowLong = 300; }
            else { HowLong = _lastposition > whereto ? (_lastposition - whereto) / 3 : (whereto - _lastposition) / 3; }
            Debug.Print("" + HowLong);
            Thread.Sleep((int)HowLong);
            whatservo.SetPulse(0, whereto);
            _lastposition = whereto;
            if (sleep != 0) { Thread.Sleep(sleep); }
        }

        static int TiltToServoPulse(double Tilt)
        {
            double pulse = 0;
            Tilt = Tilt - 1;
            double calc1 = Tilt / 18;
            pulse = (calc1 * 1000) + 1000;
            return (int)pulse;
        }
    }
}

..and a video of the results:
http://www.youtube.com/watch?v=xTijhSgqMfM

Jason

Very nice! Good work!

I can't wait for my netduino to show up sometime next week!

[Chris Walker]

Jason, That's pretty awesome. Once you get it cleaned up, we'd love to showcase this for a while on the Projects page... If you'd be interested in that... We love showing off the cool things that community members build. Chris

[Chris Seto]

Very nice! Now, just get another servo, a sheet of plywood and make yourself a tilt maze. You could use light sensors to detect where the ball is and include random events to make the game harder, like maybe the axises would swap in the middle of a game.

[Jason Smith]

Jason,

That's pretty awesome. Once you get it cleaned up, we'd love to showcase this for a while on the Projects page... If you'd be interested in that... We love showing off the cool things that community members build.

Chris

Thanks Chris! That sounds great! I will work on getting everything working a bit better this weekend and post my results here in the forum.

Jason.

[Jason Smith]

Very nice!

Now, just get another servo, a sheet of plywood and make yourself a tilt maze. You could use light sensors to detect where the ball is and include random events to make the game harder, like maybe the axises would swap in the middle of a game.

Very true! I think it would actually be pretty simple to do something like this. Would probably be a fun little game.

Jason.

[Jim B]

Thanks! I was able to get readings quickly using the snippet you provided. One thing, though... I had to change 21 to 31 in the computation method. This changed my 'at rest' readings to all 0's, and gave pos/neg values when I tilted the accelerometer. Thanks again! Jim B