First try on working with Saitek X52Pro MFD

Saitek_X52Pro_DirectOutput.ps1

[string]$dll = (gi HKLM:\SOFTWARE\Saitek\DirectOutput).GetValue('DirectOutput_Saitek').Replace('\', '\\')
Add-Type -Namespace Saitek -Name "DirectOutput" -UsingNamespace "System.Collections.Generic" -MemberDefinition @"
[UnmanagedFunctionPointer(CallingConvention.StdCall)] private delegate void Pfn_DirectOutput_EnumerateCallback(IntPtr hDevice, IntPtr pCtxt);
[UnmanagedFunctionPointer(CallingConvention.StdCall)] private delegate void Pfn_DirectOutput_DeviceChange(IntPtr hDevice, bool bAdded, IntPtr pCtxt);
[UnmanagedFunctionPointer(CallingConvention.StdCall)] private delegate void Pfn_DirectOutput_PageChange(IntPtr hDevice, uint dwPage, bool bSetActive, IntPtr pCtxt);
[UnmanagedFunctionPointer(CallingConvention.StdCall)] private delegate void Pfn_DirectOutput_SoftButtonChange(IntPtr hDevice, uint dwButtons, IntPtr pCtxt);

[DllImport("$dll", SetLastError = true, CharSet = CharSet.Ansi)] public static extern IntPtr DirectOutput_Initialize([MarshalAs(UnmanagedType.LPWStr)]System.Text.StringBuilder wszPluginName);
[DllImport("$dll", SetLastError = true)] public static extern IntPtr DirectOutput_Deinitialize();
[DllImport("$dll", SetLastError = true)] private static extern IntPtr DirectOutput_RegisterDeviceCallback(Pfn_DirectOutput_DeviceChange pfnCb, IntPtr pCtxt);
[DllImport("$dll", SetLastError = true)] private static extern IntPtr DirectOutput_Enumerate(Pfn_DirectOutput_EnumerateCallback pfnCb, IntPtr pCtxt);
[DllImport("$dll", SetLastError = true)] private static extern IntPtr DirectOutput_RegisterPageCallback(IntPtr hDevice, Pfn_DirectOutput_PageChange pfnCb, IntPtr pCtxt);
[DllImport("$dll", SetLastError = true)] private static extern IntPtr DirectOutput_RegisterSoftButtonCallback(IntPtr hDevice, Pfn_DirectOutput_SoftButtonChange pfnCb, IntPtr pCtxt);
//[DllImport("$dll", SetLastError = true)] private static extern IntPtr DirectOutput_GetDeviceType(IntPtr hDevice, LPGUID pGuid);
//[DllImport("$dll", SetLastError = true)] private static extern IntPtr DirectOutput_GetDeviceInstance(IntPtr hDevice, LPGUID pGuid);
[DllImport("$dll", SetLastError = true, CharSet = CharSet.Ansi)] private static extern IntPtr DirectOutput_SetProfile(IntPtr hDevice, uint cchProfile, [MarshalAs(UnmanagedType.LPWStr)]System.Text.StringBuilder wszProfile);
[DllImport("$dll", SetLastError = true)] private static extern IntPtr DirectOutput_AddPage(IntPtr hDevice, uint dwPage, uint dwFlags);
[DllImport("$dll", SetLastError = true)] private static extern IntPtr DirectOutput_RemovePage(IntPtr hDevice, uint dwPage);
[DllImport("$dll", SetLastError = true)] private static extern IntPtr DirectOutput_SetLed(IntPtr hDevice, uint dwPage, uint dwIndex, uint dwValue);
[DllImport("$dll", SetLastError = true, CharSet = CharSet.Ansi)] private static extern IntPtr DirectOutput_SetString(IntPtr hDevice, uint dwPage, uint dwIndex, uint cchValue, [MarshalAs(UnmanagedType.LPWStr)]System.Text.StringBuilder wszValue);
[DllImport("$dll", SetLastError = true)] private static extern IntPtr DirectOutput_SetImage(IntPtr hDevice, uint dwPage, uint dwIndex, uint cbValue, IntPtr pvValue);
[DllImport("$dll", SetLastError = true, CharSet = CharSet.Ansi)] private static extern IntPtr DirectOutput_SetImageFromFile(IntPtr hDevice, uint dwPage, uint dwIndex, uint cchFilename, [MarshalAs(UnmanagedType.LPWStr)]System.Text.StringBuilder wszFilename);

private static bool _test(IntPtr a) {
    if (a == IntPtr.Zero)
        return true;
    System.Runtime.InteropServices.Marshal.ThrowExceptionForHR(a.ToInt32());
    return false;
}

public class Device {
    public class Page {
        public Device Owner;
        public uint Id;
        private string _Line0;
        private string _Line1;
        private string _Line2;
        public string Line0 {
            get { return _Line0; }
            set { if (_set_string(0, value)) _Line0 = value; }
        }
        public string Line1 {
            get { return _Line1; }
            set { if (_set_string(1, value)) _Line1 = value; }
        }
        public string Line2 {
            get { return _Line2; }
            set { if (_set_string(2, value)) _Line2 = value; }
        }

        public Page(Device owner, uint id, bool Active = false) {
            Owner = owner;
            Id = id;
            _Line0 = "";
            _Line1 = "";
            _Line2 = "";

            _test(DirectOutput_AddPage(Owner.hDevice, Id, Convert.ToUInt32(Active ? 1 : 0)));
        }
        private bool _set_string(uint Line, string Value) {
            System.Text.StringBuilder sb = new System.Text.StringBuilder(Value);
            return _test(DirectOutput_SetString(Owner.hDevice, Id, Line, Convert.ToUInt32(Value.Length), sb));            
        }
    };

    public class PageChangeEventArgs : EventArgs {
        public Device Device;
        public Page Page;
        public bool SetActive;
        public PageChangeEventArgs(Device device, Page page, bool setActive) {
            Device = device;
            Page = page;
            SetActive = setActive;
        }
    };
    public class ButtonEventArgs : EventArgs {
        public Device Device;
        public uint Button;
        public long Duration;
        public ButtonEventArgs(Device device, uint button, long duration) {
            Device = device;
            Button = button;
            Duration = duration;
        }
    };


    public IntPtr hDevice;
    public List<Page> Pages;
    public Page ActivePage;
    
    public event EventHandler<PageChangeEventArgs> PageChange;
    public event EventHandler<ButtonEventArgs> ButtonDown;
    public event EventHandler<ButtonEventArgs> ButtonPress;
    public event EventHandler<ButtonEventArgs> ButtonLongPress;
    public event EventHandler<ButtonEventArgs> ButtonUp;

    private Pfn_DirectOutput_PageChange _PageChangeCallback;
    private Pfn_DirectOutput_SoftButtonChange _SoftButtonChangeCallback;

    private System.Timers.Timer ButtonUpTimer;
    private System.Diagnostics.Stopwatch ButtonDownStopWatch;
    private uint ActiveButton; // currently pressed button id; 0 if no key is pressed

    public Device(IntPtr Device) {
        hDevice = Device;
        Pages = new List<Page>();
        ActivePage = new Page(this, 0, true);
        Pages.Add(ActivePage);

        ButtonUpTimer = new System.Timers.Timer(100);
        ButtonUpTimer.Elapsed += (sender, e) => {
            ButtonDownStopWatch.Stop();
            ButtonUpTimer.Enabled = false;
            var button = ActiveButton;
            ActiveButton = 0;
            OnButtonUp(this, new ButtonEventArgs(this, button, ButtonDownStopWatch.ElapsedMilliseconds));
        };

        ButtonDownStopWatch = new System.Diagnostics.Stopwatch();

        _PageChangeCallback = new Pfn_DirectOutput_PageChange(_onPageChange);
        _test(DirectOutput_RegisterPageCallback(hDevice, _PageChangeCallback, IntPtr.Zero));

        _SoftButtonChangeCallback = new Pfn_DirectOutput_SoftButtonChange(_onButtonDown);
        _test(DirectOutput_RegisterSoftButtonCallback(hDevice, _SoftButtonChangeCallback, IntPtr.Zero));
    }

    private void _onPageChange(IntPtr hDevice, uint dwPage, bool bSetActive, IntPtr pCtxt) {
        var Page = Pages.Find(page => page.Id == dwPage);
        
        if (bSetActive)
            ActivePage = Page;

        EventHandler<PageChangeEventArgs> handler = PageChange;
        if (handler != null)
            handler(this, new PageChangeEventArgs(this, Page, bSetActive));
    }
    private void _onButtonDown(IntPtr hDevice, uint dwButton, IntPtr pCtxt) {
        if ((dwButton & 1) == 1) // every button that is sended simultaneously with ok/select
            dwButton = 1; // is only passed as ok/select

        long duration = ButtonDownStopWatch.ElapsedMilliseconds;
        if (dwButton == 0) { // holding buttons 1,2,4 and page-buttons are sending 0
            if (ActiveButton > 0) {
                ButtonUpTimer.Stop();
                ButtonUpTimer.Start(); // reset Timer
            }
        } else {
            ButtonUpTimer.Stop();
            ActiveButton = dwButton;
            ButtonUpTimer.Enabled = true;
            ButtonUpTimer.Start();
            ButtonDownStopWatch.Restart();
            duration = 0;

            OnButtonDown(this, new ButtonEventArgs(this, dwButton, duration));
        }

        if (ActiveButton > 0)
            OnButtonPress(this, new ButtonEventArgs(this, ActiveButton, duration));

        if (duration > 750) {// long click ms
            ButtonDownStopWatch.Restart();
            OnButtonLongPress(this, new ButtonEventArgs(this, ActiveButton, duration));
        }
    }
    protected void OnButtonDown(object sender, ButtonEventArgs args) {
        EventHandler<ButtonEventArgs> handler = ButtonDown;
        if (handler != null)
            handler(this, args);
    }
    protected void OnButtonPress(object sender, ButtonEventArgs args) {
        EventHandler<ButtonEventArgs> handler = ButtonPress;
        if (handler != null)
            handler(this, args);
    }
    protected void OnButtonLongPress(object sender, ButtonEventArgs args) {
        EventHandler<ButtonEventArgs> handler = ButtonLongPress;
        if (handler != null)
            handler(this, args);
    }
    protected void OnButtonUp(object sender, ButtonEventArgs args) {
        EventHandler<ButtonEventArgs> handler = ButtonUp;
        if (handler != null)
            handler(this, args);
    }
};

public static bool Init(String Name) {
    System.Text.StringBuilder sb = new System.Text.StringBuilder(Name);
    if (_test(DirectOutput_Initialize(sb))) {

        _DeviceChangeCallback = new Pfn_DirectOutput_DeviceChange(_onDeviceChange);
        _EnumerateCallback = new Pfn_DirectOutput_EnumerateCallback(_onEnumerate);    
        return _test(DirectOutput_RegisterDeviceCallback(_DeviceChangeCallback, IntPtr.Zero)) && _test(DirectOutput_Enumerate(_EnumerateCallback, IntPtr.Zero));
    }
    return false;
}

public static bool Reset() {
    return _test(DirectOutput_Deinitialize());
}

public class DeviceChangeEventArgs : EventArgs {
    public bool Added;
};
public static event EventHandler<DeviceChangeEventArgs> DeviceChange;
private static Pfn_DirectOutput_DeviceChange _DeviceChangeCallback;
private static Pfn_DirectOutput_EnumerateCallback _EnumerateCallback;

public static List<Device> Devices = new List<Device>();

private static void _onDeviceChange(IntPtr hDevice, bool bAdded, IntPtr pCtxt) {
    Device dev = Devices.Find(device => device.hDevice == hDevice);

    if (dev == null) {
        if (bAdded) {
            dev = new Device(hDevice);
            Devices.Add(dev);
        }
    } else {
        if (!bAdded)
            Devices.Remove(dev);
    }
    
    EventHandler<DeviceChangeEventArgs> handler = DeviceChange;
    if (handler != null) {
        DeviceChangeEventArgs args = new DeviceChangeEventArgs();
        args.Added = bAdded;
        handler(dev, args);
    }
}
private static void _onEnumerate(IntPtr hDevice, IntPtr pCtxt) {
    if (Devices.Find(device => device.hDevice == hDevice) == null)
        Devices.Add(new Device(hDevice));
}
"@

$DirectOutput = [Saitek.DirectOutput]

function Initialize-DirectOutput ([string]$PluginName)
{
    $DirectOutput::Init($PluginName)
}
function Deinitialize-DirectOutput
{
    $DirectOutput::Reset()
}
function Get-DirectOutputDevices
{
    $DirectOutput::Devices
}
function Write-MFD ([string] $Line0="", [string] $Line1="", [string] $Line2="", $Device=(Get-DirectOutputDevices|select -f 1))
{
    $Device.ActivePage.Line0 = $Line0
    $Device.ActivePage.Line1 = $Line1
    $Device.ActivePage.Line2 = $Line2
}

# examples:
Deinitialize-DirectOutput | Out-Null
Initialize-DirectOutput "app" | Out-Null

Register-ObjectEvent -InputObject $DirectOutput::Devices[0] -EventName PageChange -Action {
    Param([Saitek.DirectOutput+Device]$Device, [Saitek.DirectOutput+Device+PageChangeEventArgs]$EventArgs)
    Write-Host "Page: $($EventArgs.Page.Id) Active: $($EventArgs.SetActive)"
} | Out-Null
Register-ObjectEvent -InputObject $DirectOutput::Devices[0] -EventName ButtonDown -Action {
    Param([Saitek.DirectOutput+Device]$Device, [Saitek.DirectOutput+Device+ButtonEventArgs]$EventArgs)
    Write-Host "Button $($EventArgs.Button) pressed down"
} | Out-Null
<#Register-ObjectEvent -InputObject $DirectOutput::Devices[0] -EventName ButtonPress -Action {
    Param([Saitek.DirectOutput+Device]$Device, [Saitek.DirectOutput+Device+ButtonEventArgs]$EventArgs)
    Write-Host "Button $($EventArgs.Button) pressed"
} | Out-Null#>
Register-ObjectEvent -InputObject $DirectOutput::Devices[0] -EventName ButtonLongPress -Action {
    Param([Saitek.DirectOutput+Device]$Device, [Saitek.DirectOutput+Device+ButtonEventArgs]$EventArgs)
    Write-Host "Button $($EventArgs.Button) pressed long"
} | Out-Null
Register-ObjectEvent -InputObject $DirectOutput::Devices[0] -EventName ButtonUp -Action {
    Param([Saitek.DirectOutput+Device]$Device, [Saitek.DirectOutput+Device+ButtonEventArgs]$EventArgs)
    Write-Host "Button $($EventArgs.Button) released"
} | Out-Null

<#Register-ObjectEvent -InputObject $DirectOutput -EventName DeviceChange -Action {
    Param([Saitek.DirectOutput+Device]$Device, [Saitek.DirectOutput+DeviceChangeEventArgs]$EventArgs)
    Write-Host "Device changed: $($EventArgs.Added)"
} | Out-Null#>