15. Human Interface Devices

Question 1

Cos’è una Human Device Interface?

Answer 1

A human interface device or HID is a type of computer device usually used by humans.
HID takes input from humans and gives output to humans.
The term “HID” is used to indicate the physical devices and also the USB-HID specification.

Question 2

Perchè usare HDI?

Answer 2

The HID protocol makes implementation of devices very simple.
Devices define their data packets and then present a “HID descriptor” to the host.

Question 3

Cosa deve fare l’host?

Answer 3

The host is expected to be a more complex entity than the device. The host needs to retrieve the HID descriptor from the device and parse it before it can fully communicate with the device.

Question 4

descrivi HID report protocol

Answer 4

Devices define their data packets and then present a “HID descriptor” to the host.
The HID descriptor is a hard coded array of bytes that describes the device’s
data packets.
This includes:
● how many packets the device supports,
● the size of the packets,
● the purpose of each byte and bit in the packet.
For example, a keyboard with a calculator program button can tell the host that the
button’s pressed/released state is stored as the 2nd bit in the 6th byte in data

Question 5

descrivi HID boot protocol

Answer 5

In boot protocol, only specific
devices are supported with only specific features because fixed data packet
formats are used.
The HID descriptor is not used in this mode so innovation is limited.
However, the benefit is that minimal functionality is still possible on hosts that
otherwise would be unable to support HID.
The only devices supported in boot protocol are: Keyboard and Mouse

Question 6

In quante categorie puoi dividere i dispositivi HID?

Answer 6

input devices,
output devices

Question 7

Descrivi gli input devices

Answer 7

Input devices are based on sensors (a device, module, or subsystem whose
purpose is to detect events or changes in the physical world its environment and
convert it in analog or digital electronic information)

Question 8

Descrivi gli output devices

Answer 8

Output devices are based on actuators (a device, module, or subsystem whose
purpose is to convert analog or digital electronic signals in physical events aimed
at changing the physical)

Question 9

layout : fisico vs visivo vs funzionale

Answer 9

Physical layout is the actual positioning of keys on a keyboard.
Visual layout the arrangement of the legends (labels, markings, engravings) that appear on those keys.
Functional layout is the arrangement of the key-meaning association or keyboard
mapping, determined in software, of all the keys of a keyboard: this (rather than
the legends) determines the actual response to a key press.

Question 10

Can keyboard be dynamically mapped?

Answer 10

keyboards are designed to send a scancode to the operating
system (OS) when a key is pressed or released: this code reports only the key’s
row and column, not the specific character engraved on that key.

Question 11

RFID

Answer 11

Il sistema RFID è composto principalmente da due componenti: un tag (o etichetta) RFID e un lettore RFID.
Unlike a barcode, the tag doesn’t need to be within the line of sight of the reader, so it may be embedded in the tracked object.

Question 12

NFC

Answer 12

Near field communication
NFC offers a low-speed connection with simple setup that can be used to
bootstrap more-capable wireless connections.

Question 13

Cos’è un pointing device?

Answer 13

A pointing device is an input interface that allows a user to input spatial (i.e., continuous and multi-dimensional) data to a computer.
Movements of the pointing device are echoed on the screen by movements
of the pointer (or cursor) and other visual changes.

Question 14

Cosa dice la Fitts’s law

Answer 14

This scientific law predicts that the time required
to rapidly move to a target area is a function
of the ratio between the distance (D) to the
target and the width of the target (W).

Question 15

Classificazione dei pointing devices

Answer 15

direct,indirect, absolute, relative, isotonic, elastic, isometric, position controll vs rate controll

Question 16

Spiega direct input

Answer 16

In case of a direct-input pointing device, the on-screen pointer is at the same
physical position as the pointing device (e.g., finger on a touch screen, stylus
on a tablet computer).

Question 17

Spiega indirect input

Answer 17

An indirect-input pointing device is not at the same physical position as the
pointer but translates its movement onto the screen (e.g., computer mouse,
joystick, stylus on a graphics tablet).

Question 18

Spiega absolute movement

Answer 18

An absolute-movement input device (e.g., stylus, finger on touch screen) provides
a consistent mapping between a point in the input space (location/state of the
input device) and a point in the output space (position of pointer on screen).

Question 19

Spiega relative movement

Answer 19

A relative-movement input device (e.g., mouse, joystick) maps displacement in the
input space to displacement in the output state. It therefore controls the relative
position of the cursor compared to its initial position.

Question 20

speiga isotonic pointing devices

Answer 20

An isotonic pointing device is movable and measures its displacement

Question 21

Spiega isometric pointing devices

Answer 21

isometric device is fixed and measures the force
which acts on

Question 22

Spiega elastic pointing devices

Answer 22

An elastic device
increases its force resistance with displacement (joystick).

Question 23

Spiega position control

Answer 23

A position-control input device (e.g., mouse, finger on touch screen) directly
changes the absolute or relative position of the on-screen pointer.

Question 24

Spiega rate control

Answer 24

A rate-control input device (e.g., trackpoint, joystick) changes the speed and direction of the movement of the on-screen pointer.

Question 25

Spiega eye tracking

Answer 25

An eye tracker is a device for measuring eye positions and eye movement.

Question 26

Come funziona un eye tracking device?

Answer 26

The most widely used current designs are video-based eye-trackers.
A camera focuses on one or both eyes and records eye movement. Most
modern eye-trackers use the center of the pupil and infrared/near-infrared
non-collimated light to create corneal reflections (CR).

Question 27

Bright-pupil (top) and dark-pupil (center)

Answer 27

Their difference is based on the location of the illumination source with respect to the optics.
in più c’è passive light (bottom). It uses visible
light to illuminate.
Bright : If the illumination is coaxial with the optical path, then the eye acts as a
retroreflector as the light reflects off the retina creating a bright pupil effect similar
to red eye. Bright-pupil tracking creates greater iris/pupil contrast, allowing more robust
eye-tracking with all iris pigmentation, and greatly reduces interference caused by
eyelashes and other obscuring features. It also allows tracking in lighting
conditions ranging from total darkness to very bright.
Bright-pupil tracking is more reliable but require more complex hardware
setup
Dark: If the illumination source is offset from the optical path, then the pupil
appears dark because the retroreflection from the retina is directed away from the
camera.

Question 28

Data Glove

Answer 28

Un guanto cablato (o “dataglove”) è un dispositivo di input indossabile per l’interazione uomo-computer. Utilizza diverse tecnologie di sensori per rilevare dati fisici, come il piegamento delle dita. Spesso è dotato di un tracker di movimento per catturare la posizione/rotazione globale del guanto. I movimenti rilevati vengono interpretati dal software del guanto, trasformando ogni gesto in informazioni utili, come riconoscere la lingua dei segni o altre funzioni simboliche.

Question 29

Haptic devices

Answer 29

I dispositivi aptici (o interfacce aptiche) sono dispositivi meccanici che facilitano la comunicazione tra l’utente e il computer. Consentono agli utenti di toccare, sentire e manipolare oggetti tridimensionali in ambienti virtuali e sistemi tele-operati. A differenza dei comuni dispositivi di interfaccia come mouse e joystick, che sono solo dispositivi di input, i dispositivi aptici sono dispositivi di input-output: registrano le manipolazioni fisiche dell’utente (input) e forniscono sensazioni tattili realistiche coordinate con eventi visualizzati sullo schermo (output).

Question 30

Smart Paper, Whiteboards and similars

Answer 30

Negli ultimi anni sono stati sviluppati nuovi dispositivi con l’obiettivo di digitalizzare l’interazione dell’utente con carta e lavagna. Questi dispositivi digitalizzano la scrittura dell’utente tramite penne intelligenti tracciate e/o superfici sensorizzate. Si tratta di un’interfaccia che incrocia diverse categorie, dove il puntamento e le immagini vengono utilizzati come input combinati.

Question 31

Cos’è un image sensor?

Answer 31

An image sensor is a sensor that detects and conveys information used to make an image.

Question 32

3d image capture device

Answer 32

3D scanning is the process of analyzing a real-world object or environment
to collect data on its shape and possibly its appearance (e.g. colour).

Question 33

In quante e quali categorie puoi dividere la 3d scanning technology?

Answer 33

Passive and
Active

Question 34

Descrivi il passive scanning

Answer 34

Passive 3D imaging solutions do not emit any kind of radiation
themselves, but instead rely on detecting reflected ambient radiation.
Most solutions of this type detect visible light because it is a readily available
ambient radiation.
Other types of radiation, such as infrared could also be used. Passive methods
can be very cheap, because in most cases they do not need particular hardware
but simple digital cameras.
Stereoscopic cameras are the most common passive 3D scanning systems

Question 35

Descrivi un sistema stereoscopico

Answer 35

usually employ two video cameras, slightly apart, looking
at the same scene. By analysing the slight differences between the images seen
by each camera, it is possible to determine the distance at each point in the
images. This method is based on the same principles driving human stereoscopic
vision.

Question 36

Descrivi il sistema Photometric

Answer 36

usually use a single
camera, but take multiple
images under varying
lighting conditions. These
techniques attempt to
invert the image formation
model in order to recover
the surface orientation at
each pixel.

Question 37

Descrivi la Silhouette technique

Answer 37

use outlines
created from a sequence of photographs
around a three-dimensional object
against a well contrasted background.
These silhouettes are extruded and
intersected to form the visual hull
approximation of the object. With these
approaches some concavities of an
object (like the interior of a bowl) cannot
be detected.

Question 38

Descrivi l’active scanning

Answer 38

Active scanners emit some kind of radiation or light and detect its reflection or
radiation passing through object in order to probe an object or environment.
Possible types of emissions used include light, ultrasound or x-ray.
Various typologies: Time-of-flight, Triangulation, Structured light, Modulated Light

Question 39

Desctrivi The time-of-flight

Answer 39

Uno scanner laser 3D è uno scanner attivo che utilizza la luce laser per esaminare un oggetto. Al centro di questo tipo di scanner c’è un telemetro laser basato sul tempo di volo. Il telemetro misura la distanza di una superficie calcolando il tempo che la luce impiega per fare il viaggio di andata e ritorno. Viene emesso un impulso di luce laser e viene misurato il tempo che impiega la luce riflessa per essere rilevata dal dispositivo. Circa 3,3 picosecondi è il tempo che la luce impiega per viaggiare 1 millimetro. Lo scanner laser rileva la distanza di un solo punto per volta nel suo campo visivo, cambiando la direzione del telemetro per scansionare l’intero campo.

Question 40

Descrivi Triangulation

Answer 40

Gli scanner laser 3D basati sulla triangolazione sono anch’essi scanner attivi che usano la luce laser per esplorare l’ambiente. A differenza degli scanner laser 3D a tempo di volo, lo scanner laser di triangolazione illumina l’oggetto con un laser e utilizza una telecamera per individuare la posizione del punto laser. A seconda di quanto lontano il laser colpisce una superficie, il punto laser appare in posizioni diverse nel campo visivo della telecamera. Questa tecnica è chiamata triangolazione perché il punto laser, la telecamera e l’emettitore laser formano un triangolo.

Question 41

Modulated light 3D scanners

Answer 41

Gli scanner 3D a luce modulata proiettano sulla superficie oggetto una luce continuamente variante, generalmente modulando la sua ampiezza secondo un modello sinusoidale. Una telecamera rileva la luce riflessa e la quantità di spostamento del modello determina la distanza percorsa dalla luce. La luce modulata consente inoltre allo scanner di ignorare la luce proveniente da fonti diverse dal laser, eliminando così ogni interferenza.

Question 42

What is a IMU Inertial Measurement Unit

Answer 42

is an electronic device that measures and
reports a body’s specific force, angular rate, and sometimes the orientation of
the body, using a combination of accelerometers, gyroscopes, and sometimes
magnetometers.
9-Axis devices combine a 3-axis
gyroscope, 3-axis accelerometer and
3-axis compass (magnetometer) in the
same chip together with an onboard
Digital Motion Processor capable of
processing the complex MotionFusion
algorithms