Chapter 31 · Keyboard and Mouse Internals

Practical Lab: Input Exploration

7 min read

Objective

Find your own keyboard and mouse in Windows, see how they are connected, watch how Windows treats the keys, and look at the pointer and key-repeat settings. This lab only looks. The one optional step that changes something (pointer speed) is harmless and has undo steps.

Time: 25–30 minutes
You need: A Windows PC with a keyboard and mouse. No extra software. (Third-party "polling rate test" tools are not used.)

What to Open

ToolHow to open it
Device ManagerPress Win + X, then choose Device Manager
PowerShellPress Win, type PowerShell, press Enter (normal, not admin)
NotepadPress Win, type Notepad, press Enter
On-Screen KeyboardPress Win + R, type osk, press Enter
SettingsPress Win + I

Part 1: Find Your Devices (Device Manager)

Open Device Manager and expand these three branches:

  • Keyboards
  • Mice and other pointing devices
  • Human Interface Devices
  1. How many entries are under Keyboards? ________________
  2. Name the entries under Mice and other pointing devices: ________________
  3. Under Human Interface Devices, you will probably see lines like USB Input Device and HID-compliant mouse or HID Keyboard Device. How many lines are there? ________________

A laptop usually shows a Standard PS/2 Keyboard for its built-in keyboard. That is normal: laptops often connect the keyboard internally in the old PS/2 style. It does not mean the keyboard has a round plug.

Part 2: Ask PowerShell (Same Facts, Another Way)

Type each line and press Enter:

Get-PnpDevice -Class Keyboard
Get-PnpDevice -Class Mouse
Get-PnpDevice -Class HIDClass | Select-Object -First 15 Status, FriendlyName
Get-CimInstance Win32_Keyboard | Select-Object Name, Description, DeviceID
Get-CimInstance Win32_PointingDevice | Select-Object Name, Manufacturer, DeviceID

Look at the DeviceID text of your keyboard and mouse.

  1. Does a DeviceID start with HID, USB, ACPI, or ROOT? ________________
  2. If one starts with ACPI (laptop keyboard) or has "PS2" in it, what old connection style is in use? ________________
  3. Do the Get-PnpDevice lines show Status OK? ________________

Status OK only means the driver loaded. Devices that are listed but not currently plugged in may show other states.

Part 3: See the USB Path (Device Manager)

  1. In Device Manager choose View → Devices by connection.
  2. Expand ACPI x64-based PC → Microsoft ACPI-Compliant System → PCI Express Root Complex and keep opening the branches until you find an item named USB xHCI Compliant Host Controller (or USB Root Hub).
  3. Open it. You should find a USB Root Hub, and below it USB Composite Device or USB Input Device, and below those your keyboard or mouse (HID Keyboard Device, HID-compliant mouse).
USB xHCI Compliant Host Controller      ← Section 2.1: the polling chip
 └─ USB Root Hub (USB 3.0)
     └─ USB Input Device                ← the HID class device
         └─ HID Keyboard Device         ← kbdhid sees this one
  1. How many levels are there between the host controller and your keyboard? ________________
  2. A wireless dongle keyboard or mouse appears like a normal USB item here. Is any of yours wireless? ________________
  3. Return to View → Devices by type when finished.

Part 4: Watch the Layers Work (Notepad)

Open Notepad and try each of these. Write what happens.

Try thisWhat you should seeWhich Section it proves
Type a, then hold Shift and type aa then A3.5: the same key gives two characters
Press Caps Lock and look at the keyboard lamp (or the on-screen Caps indicator)Lamp lights, letters become capital2.1: the PC sends the lamp state back to the keyboard
Hold down a letter key for a secondA pause, then repeated letters2.1: the repeat is created by Windows
Hold Ctrl and press AAll text selected3.6: combos are keys that the program interprets
Hold two letter keys togetherBoth letters appear1.5: rollover (try 4 to 6 keys: most keyboards cope)
Press Win + Space (if you have 2 or more layouts)The layout name changes in the taskbar3.5: Windows swaps the translation table

Part 5: Software Can Inject Keys (On-Screen Keyboard)

  1. Start osk.exe as in the table above.

  2. Click in Notepad, then click letters on the on-screen keyboard with the mouse.

  3. Letters appear in Notepad exactly as if typed.

  4. Why does Notepad not care whether the key came from a real keyboard or from the on-screen one? (Hint: Section 3, step 5 to 7.)

The on-screen keyboard works because Windows has a documented way for programs to send key events into the input system. Everything after that point (layout, messages, drawing) is identical to a real key press.

Close the on-screen keyboard when done.

Part 6: Key Repeat and Layout Settings (Read-Only Look)

  1. Press Win + R, type control keyboard, press Enter. The classic Keyboard Properties window opens. Look at Repeat delay and Repeat rate. Do not change them. Close the window.
  2. In PowerShell:
Get-WinUserLanguageList
Get-ItemProperty 'HKCU:\Control Panel\Keyboard' | Select-Object KeyboardDelay, KeyboardSpeed
  1. Which languages are listed, and what is the InputMethodTips number for your layout? ________________
  2. What are your KeyboardDelay and KeyboardSpeed values? ________________ (Values are small whole numbers. Exact meaning may differ by version, but a bigger speed number means faster repeat.)

Part 7: Pointer Settings (Read-Only, Plus One Optional Reversible Test)

  1. Open Settings → Bluetooth & devices → Mouse. Note your Mouse pointer speed value (a slider; the default is usually near the middle).
  2. Press Win + R, type control mouse, press Enter. On the Pointer Options tab, find Enhance pointer precision. Note whether it is ticked.
  3. In PowerShell:
Get-ItemProperty 'HKCU:\Control Panel\Mouse' | Select-Object MouseSpeed, MouseSensitivity, MouseThreshold1, MouseThreshold2
  1. Pointer speed (Settings): ________________ Enhance pointer precision: On / Off
  2. Registry values: MouseSensitivity ________________ (this is the slider, on a scale of 1 to 20, where 10 is the usual default).

Optional reversible test (changes a setting, harmless):

  1. Write down your current pointer speed from step 1.
  2. Move the slider one notch lower, then wave the mouse across your desk. Note the change.
  3. Return the slider to the exact value you wrote down.
  4. If you try the Enhance pointer precision checkbox, put it back as it was.

Undo: set the slider and the checkbox back to the original values noted above. Nothing else changes.

What Should Happen

  • Part 1 and 2 show the same devices from two angles.
  • Part 3 shows the real USB path: controller, hub, device, HID entry.
  • Part 4 and 5 show that the layout, repeat and key messages are done by Windows, not by the keyboard.
  • Part 6 and 7 show the settings that Windows applies to keys and mouse counts.

Interpretation Guide

What you seeWhat it means
Keyboard DeviceID starts with HID\The keyboard uses the HID class (USB or Bluetooth)
DeviceID has ACPI\ or PS2 textA built-in laptop keyboard or older PS/2 style
"HID-compliant mouse" under Human Interface DevicesStandard HID class driver in use, no maker driver needed
Maker's name in the entry (a gaming brand, for example)Extra maker software or a maker driver is present on top
Device listed with a yellow warning markDriver problem; see Chapter 14
MouseSpeed = 1 (or 2) with thresholdsEnhance pointer precision is on (values may differ)
MouseSpeed = 0Acceleration is off
Letters wrong on a keyA different layout is active (Win + Space)

Follow-Up Questions

  1. Why does a wireless 2.4 GHz mouse appear as an ordinary USB HID mouse?
  2. Your laptop keyboard shows "Standard PS/2 Keyboard", yet there is no PS/2 socket. How can that be?
  3. What does it prove that the on-screen keyboard can type into Notepad?
  4. If you swapped to a French layout, which parts of the chain from Section 3 would change, and which would stay the same?
  5. Why does the pointer speed slider change cursor movement even though the mouse's CPI is fixed?