sdk scan speed of HC-SR04

MikeC531

USA

Asked Apr 2011 — Edited Apr 2011

Is there a way of adusting the speed of the scan of the HC-SR04 using the SDK or do you have to do your own timing ?
I noticed in the ARC the interval changes the speed of the sweep, but i can't seem to find any interval in the SDK anywhere for interval, am I missing it somewhere ?

Thanks
Mike

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DJ Sures

PRO

Synthiam

#1 Apr 2011

Would you be able to post your code as an example for me to get an idea of where you're at?

MikeC531

USA

#2 Apr 2011

Here is the part of the code i'm working on.

private void getDistances()
{
//Start on the right side
ezb.EZB.Servo.SetServoPosition(_SCAN_SERVO_PIN, _SCAN_RIGHT_MIN);

for (int x = _SCAN_RIGHT_MIN; x <= _SCAN_LEFT_MAX; x += 2)
{

ezb.EZB.HC_SR04.MinPoolTimeMS = 1; //Doesn't seem to see all objects at times above 3

//Set the servo position to x
ezb.EZB.Servo.SetServoPosition(_SCAN_SERVO_PIN, x);

//Get the distance of the object
int distance = ezb.EZB.HC_SR04.GetDistance(_PING_TRIGGER_PIN, _PING_ECHO_PIN);

//Save the distance in an array indexed by the servo position
_markDirArray[ezb.EZB.Servo.GetServoPosition(_SCAN_SERVO_PIN)] = distance;

//Show distance and direction on screen
log("Distance: {0}, Dir: {1}", distance, ezb.EZB.Servo.GetServoPosition(_SCAN_SERVO_PIN));
}

}

private void findShortestPath()
{

log("Started");

//Set _minDist to a large number
_minDist = 100;
zz = false;
do
{
// Find all objects
getDistances();

// Get the shortest path
// getShortestDist();

// turnTowardShortest();

Application.DoEvents();
System.Threading.Thread.Sleep(1150);
} while (zz == false);
}

private void timer1_Tick(object sender, EventArgs e)
{
if (_inProgress)
return;
if (!ezb.EZB.IsConnected)
{
return;
}

_inProgress = true;

findShortestPath();

Application.DoEvents();

_inProgress = false;

}

}

DJ Sures

PRO

Synthiam

#3 Apr 2011

Here, try this. I use the timer to control the speed of the sweep. A timer is a good idea because it also allows the UI to respond. If you put the sweep in a FOR loop, then you lock up the UI thread.

Code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Tutorial_20___Find_Shortest_Path {

  public partial class Form1 : Form {

    // Used in timer to avoid double entry
    bool         _inProgress     = false; 

    // servo port of scanner
    readonly EZ_B.Servo.ServoPortEnum _SCAN_SERVO_PIN = EZ_B.Servo.ServoPortEnum.RB5;

    // HC-SR04 Sensor Pins
    readonly EZ_B.Digital.DigitalPortEnum _PING_TRIGGER_PIN = EZ_B.Digital.DigitalPortEnum.RC0;
    readonly EZ_B.Digital.DigitalPortEnum _PING_ECHO_PIN = EZ_B.Digital.DigitalPortEnum.RC1;

    // False scans right, True scans left
    bool         _scanDir        = false;

    // Array of distance values
    int [] _markDirArray = new int[EZ_B.Servo.SERVO_MAX + 1];

    public Form1() {

      InitializeComponent();

      timer1.Interval = 200;
      timer1.Start();
    }

    delegate void SetLogCallback(string text, params object[] vals);
    private void Log(string text, params object[] vals) {

      if (this.tbLog.InvokeRequired) {

        SetLogCallback d = new SetLogCallback(Log);
        this.Invoke(d, new object[] { text, vals });
      } else {

        this.tbLog.AppendText(string.Format(text, vals));
        this.tbLog.AppendText(Environment.NewLine);
      }
    }

    private void doSweepServo() {

      int currentPosition = ezb.EZB.Servo.GetServoPosition(_SCAN_SERVO_PIN);

      _markDirArray[currentPosition] = ezb.EZB.HC_SR04.GetDistance(_PING_TRIGGER_PIN, _PING_ECHO_PIN);

      Log("Position: {0}, Distance: {1}", currentPosition, _markDirArray[currentPosition]);

      if (_scanDir)
        currentPosition++;
      else
        currentPosition--;

      ezb.EZB.Servo.SetServoPosition(_SCAN_SERVO_PIN, currentPosition);

      if (currentPosition == EZ_B.Servo.SERVO_MAX)
        _scanDir = false;
      else if (currentPosition == EZ_B.Servo.SERVO_MIN)
        _scanDir = true;
    }

    private void timer1_Tick(object sender, EventArgs e) {

      if (!ezb.EZB.IsConnected)
        return;

      if (_inProgress)
        return;

      _inProgress = true;

      doSweepServo();

      _inProgress = false;
    }
  }
}