using System;
using System.Threading;
using System.IO.Ports;
using System.Text;

using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;

namespace MFConsoleApplication1
{
    public static class DGHPressure
    {
        private static char DGHTerminatingChar = '\r';
        private static string DGHRxString = "";

        private static SerialPort DGHPort = new SerialPort("COM3", 38400, Parity.None, 8, StopBits.One);
        private static AutoResetEvent DGHReadEvent = new AutoResetEvent(false);

        public static int init(String PortName)
        {
            
            DGHPort.ReadTimeout = 1000;

            DGHPort.Open();
            DGHPort.DiscardInBuffer();
            DGHPort.DiscardOutBuffer();

            DGHPort.DataReceived += new SerialDataReceivedEventHandler(DGHPort_DataReceived);
            DGHPort.ErrorReceived += new SerialErrorReceivedEventHandler(DGHPort_ErrorReceived);

            return (0);
        }

        public static double readPressure()
        {
            byte[] DGHTxBytes;
            string DGHReadCmd = "$1RD\r";       //$1RD terminated with CR is the command to read data from the DGH

            double pressureDBar = Double.NaN;
            const double ma2bar = (15.0 / 1.45038) / 16.0;     //4-20 ma transducer; 15 psig full scale; 1 dBar = 1.45038 psi
            const double maOffset = 4.0;

            EngrLog.writeEvent(Program.DateTimeNowMilliSec() + " ,Sending RD to DGH");
            DGHTxBytes = Encoding.UTF8.GetBytes(DGHReadCmd);
            DGHPort.Write(DGHTxBytes, 0, DGHTxBytes.Length);

            EngrLog.writeEvent(Program.DateTimeNowMilliSec() + " ,Waiting for DGH RD");
            if (DGHReadEvent.WaitOne(1000, false)) //waiting for notification, 1000 mSec timeout
            {
                DGHRxString = DGHRxString.Substring(2, 11);
                pressureDBar = Convert.ToDouble(DGHRxString);
                pressureDBar = (pressureDBar - maOffset) * ma2bar;
                EngrLog.writeEvent(Program.DateTimeNowMilliSec() + " ,DGH readPressure got pressure from DGH: " + pressureDBar.ToString());
            }
            else
            {
                pressureDBar = Double.NaN;
                EngrLog.writeEvent(Program.DateTimeNowMilliSec() + " ,DGH RD timed out");
            }
            
            return (pressureDBar);
        }

        static void DGHPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            char rxChar;

            while (DGHPort.BytesToRead > 0)
            {
                rxChar = (char)DGHPort.ReadByte();
                Debug.Print(rxChar.ToString());
                DGHRxString = DGHRxString + rxChar.ToString();
                if (rxChar == DGHTerminatingChar)
                    DGHReadEvent.Set();
            }
        }

        static void DGHPort_ErrorReceived(object sender, SerialErrorReceivedEventArgs e)
        {
            //Eventually
        }

    }
}