Played around with the Ping))) sensor, came up with the following code. It uses a timer to initiate the sensor reads, and an event to report to the main application. Period and Enable / Disable are supported. I attached a zip with the project.
using System;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;
namespace ParallaxSensors
{
/*******************************************************************
* Reference the following DLLs
* - Microsoft.SPOT.Hardware
* - Microsoft.SPOT.Native
* - SecretLabs.NETMF.Hardware
* - SecretLabs.NETMF.Hardware.Netduino
******************************************************************/
/// <summary>
/// Holds the distance information for the event
/// </summary>
public class PingEventArgs
{
public PingEventArgs(int distance)
{
Distance = distance;
}
public int Distance { get; set; }
}
/// <summary>
/// Implements a timer based distance measurement of distance (in cm) using the
/// parallax Ping sensor
///
/// Example usage:
/// public static void Main()
/// {
/// Ping ping = new Ping(Pins.GPIO_PIN_D2, 1000, true);
/// ping.RangeEvent += new Ping.RangeTakenDelegate(ping_RangeEvent);
///
/// // Sleep forever!
/// Thread.Sleep(Timeout.Infinite);
/// }
///
/// static void ping_RangeEvent(object sender, PingEventArgs e)
/// {
/// Debug.Print("Range: " + e.Distance + " cm");
/// }
/// </summary>
public class Ping
{
public delegate void RangeTakenDelegate(object sender, PingEventArgs e);
public event RangeTakenDelegate RangeEvent;
private TristatePort _port;
private ExtendedTimer _timer;
private int _period;
private bool _enabled;
/// <summary>
/// Constructor: initializes the Ping class
/// </summary>
/// <param name="pin">which pin the sensor is connected to</param>
/// <param name="period">time between pulses in millisec, minimum of 1000</param>
/// <param name="enabled">if true, start pinging immediately, otherwise wait for enable</param>
public Ping(Cpu.Pin pin, int period, bool enabled)
{
_port = new TristatePort(pin, false, false, ResistorModes.Disabled);
// Initially set as disabled.
_timer = new ExtendedTimer(TakeMeasurement, null, Timeout.Infinite, period);
// Store the current period
Period = period;
// Set the enabled state
Enabled = enabled;
}
/// <summary>
/// Enable or disable the timer that triggers the read.
/// </summary>
public bool Enabled
{
get { return _enabled; }
set
{
_enabled = value;
_timer.Change((_enabled) ? 0 : Timeout.Infinite, Period);
}
}
/// <summary>
/// Set the period of pings, min is 1000ms
/// </summary>
public int Period
{
get { return _period; }
set
{
_period = value;
if (_period < 1000)
_period = 1000;
// Set enabled to the current value to force update
Enabled = _enabled;
}
}
/// <summary>
/// Get distance in cm
/// </summary>
/// <returns>distance in cm, based on wikipedia for dry air at 20C</returns>
private int GetDistance()
{
// First we need to pulse the port from high to low.
_port.Active = true; // Put port in write mode
_port.Write(true); // Pulse pin
_port.Write(false);
_port.Active = false;// Put port in read mode;
bool lineState = false;
// Wait for the line to go high, for start of pulse.
while (lineState == false)
lineState = _port.Read();
long startOfPulseAt = System.DateTime.Now.Ticks; // Save start ticks.
// Wait for line to go low.
while (lineState)
lineState = _port.Read();
long endOfPulse = System.DateTime.Now.Ticks; // Save end ticks.
int ticks = (int)(endOfPulse - startOfPulseAt);
return ticks / 580;
}
/// <summary>
/// Initiates the pulse, and triggers the event
/// </summary>
/// <param name="stateInfo"></param>
private void TakeMeasurement(Object stateInfo)
{
int distance = GetDistance();
if (RangeEvent != null)
{
RangeEvent(this, new PingEventArgs(distance));
}
}
}
}
Ping.zip 3.02KB
127 downloads
Thanks..
