Although not shown below, a few convenience functions were added such as IsError, GetBoardNum, DisplayData, CreateFileHeader and WaitForKey. To view all the functions download the complete Visual Studio 2008 project by extracting the zip file at the bottom. 

The IsError function checks the error number in the ErrorInfo object and if not zero displays the error message.  The GetBoardNum function searches for a device matching the identifying string and when found exits returning the board number assigned by InstaCal. The board number is used to get the controlling device object that has AInScan function. The CreateFileHeader writes acquisition information to the beginning of the output file. The Display data writes the data to the file and console screen. And WaitForKey does just that - waits for someone to press the spacebar.

using System;

using MccDaq;

using System.IO;

namespace AnalogInDigitalTrigger

{

    class Program

    {

        public const int BLOCKSIZE = 50;

        public const int CHANCOUNT = 4;

        public const int FIRSTCHANNEL = 0;

        public const int LASTCHANNEL = 3;

        public const int FREQ = 100;

        public const int BUFFERSIZE = BLOCKSIZE * CHANCOUNT;

        public const int HALFBUFFSIZE = BUFFERSIZE / 2;

        public const string DEVICE = "1608G";

        public static StreamWriter fStream;

        static void Main(string[] args)

        {

            MccDaq.ErrorInfo RetVal;

            int BoardNum = 0;

            int DeviceChannels = 0;

            int Rate = FREQ;

            BoardNum = GetBoardNum(DEVICE);

            if (BoardNum == -1)

                Console.WriteLine("No USB-{0} detected!", DEVICE);

            else

            {

                MccBoard daq = new MccDaq.MccBoard(BoardNum);

                daq.BoardConfig.GetNumAdChans(out DeviceChannels);

                if (DeviceChannels > 8)

                    Console.WriteLine("Single-Ended Channels");

                else

                    Console.WriteLine("Differentially-Ended Channels");

                IntPtr buffer = MccService.ScaledWinBufAllocEx(BUFFERSIZE);

                if (buffer == IntPtr.Zero)

                {

                    Console.WriteLine("Bad Handle");

                    return;

                }

                short[] chArray = new short[CHANCOUNT];

                Range[] chRange = new Range[CHANCOUNT];

                chArray[0] = 0;

                chArray[1] = 1;

                chArray[2] = 2;

                chArray[3] = 3;

                chRange[0] = Range.Bip10Volts;

                chRange[1] = Range.Bip10Volts;

                chRange[2] = Range.Bip10Volts;

                chRange[3] = Range.Bip10Volts;

                RetVal = daq.ALoadQueue(chArray, chRange, CHANCOUNT);

                IsError(RetVal);

                //specify ScanOptions.ExtTrigger to use the TRIG input 

                ScanOptions MyScanOptions = ScanOptions.Background  |

                                            ScanOptions.ScaleData   |

                                            ScanOptions.ExtTrigger  |

                                            ScanOptions.Continuous;

                //setup the acquisiton

                RetVal = daq.AInScan(   FIRSTCHANNEL,

                                        LASTCHANNEL,

                                        BUFFERSIZE,

                                        ref Rate,

                                        Range.Bip10Volts,

                                        buffer,

                                        MyScanOptions

                                    );

                IsError(RetVal);

                int Count = 0;

                int Index = 0;

                short daqStatus;

                bool ReadLower = true;

                double[] theArray = new double[BUFFERSIZE];

                fStream = new StreamWriter(@"C:\Users\Public\Documents\DataFile1608G.asc");

                CreateFileHeaders(chArray); //writes basic info to the beginning of the file

                Console.WriteLine("Waiting for External TTL trigger...Press any key to exit loop.");

                //Loop until key press

                do

                {

                    RetVal = daq.GetStatus(out daqStatus, out Count, out Index, FunctionType.AiFunction);

                    if ((Index >= HALFBUFFSIZE) & ReadLower) //check for 50% more data

                    {

                        //get lower half of buffer - ScaledWinBufToArray returns engineering units

                        RetVal = MccService.ScaledWinBufToArray(buffer, theArray, 0, HALFBUFFSIZE);

                        IsError(RetVal);

                        DisplayData(theArray, HALFBUFFSIZE / CHANCOUNT);

                        ReadLower = false; //flag that controls the next read

                    }

                    else if ((Index < HALFBUFFSIZE) & !ReadLower)

                    {

                        //get the upper half  - ScaledWinBufToArray returns engineering units

                        RetVal = MccService.ScaledWinBufToArray(buffer, theArray, HALFBUFFSIZE, HALFBUFFSIZE);

                        IsError(RetVal);

                        DisplayData(theArray, HALFBUFFSIZE / CHANCOUNT);

                        ReadLower = true;//flag that controls the next read

                    }

                } while (!Console.KeyAvailable);

                RetVal = daq.StopBackground(FunctionType.AiFunction);

                IsError(RetVal);

                MccService.WinBufFreeEx(buffer);

                WaitForKey();

            }

        }