USB ➝ HDMI | Technical features |

Mounting a smartphone to a TV with a converter
Mounting a smartphone to a TV with a converter


This type of device allows you to view the screen of a computer, tablet or smartphone via their USB port on a high-definition TV.

The HDMI connector is a connector with 19 pins, USB has only 4.
The data formats for both are very different, so even with the right conductors connected to each other, the information transferred by the computer is not recognized directly by television.
Except for MHL-enabled devices (Mobile High-definition Link)
OR recently USB-C cables (important : see below).

Micro USB cables to passive HDMI
Micro USB cables to passive HDMI

Passive MHL Cable

Indeed, there are Micro USB to HDMI cables called MHL compatible. These are not standard USB micro sockets. This MHL interface performs several simultaneous functions :
- transfer of a 1080p quality image,
- transfer of 8 uncompressed audio tracks,
- charging the phone,
- copy protection (HDCP).

In this case, the TV or HDMI-side projector must also be MHL-compatible.
Not all televisions and smartphones are equipped with these MHL-enabled ports, so check it before choosing your adaptive solution.

Micro USB cables 2.0 to HDMI active
Micro USB cables 2.0 to HDMI active

Active MHL Cable

With this type of connection, you can then look at the screen of an MHL-enabled smartphone or tablet on a non-MHL screen or projector.
This device, Plug-and-Play, is used to receive the computer's audio and video signal, via the USB port and to convert the HDMI signal.

A standard male USB cable is used to connect the converter to the computer's USB port and a standard male-male HDMI cable to connect the converter to the TV.
These converters operate with a USB port version 2.0 at least.
Power can be made by this USB port, thus avoiding any other connection or by a dedicated USB port.

The computer should be located near the television, whenever possible.
Category 1 HDMI cables can only be used up to 5 metres (15 feet) and HDMI 2 cables can only be used up to 15 metres (49 feet).

Schematic of pins connecting Micro-USB to HDMI and supporting MHL
Schematic of pins connecting Micro-USB to HDMI and supporting MHL

Micro-USB wiring to HDMI

The MHL TMDS (purple and green) data lines use differential pairs in both USB 2.0 (Data and Data) and HDMI (TMDS Data 0) and Data 0.
TMDS : Transition Minimized Differential Signaling
MHL control bus reuses identification USB On-The-Go (pin 4), and detection of hot branchING HDMI (pin 19), but respects the connection of the feed pins.

Super MHL uses a Type C USB port
Super MHL uses a Type C USB port

The Super MHL

Another type of active converter exists that uses a USB-C port.
You should know that the USB-C interface allows the transport of video and audio, it meets the Super MHL standard that comes to compete with the HDMI.

The super MHL can transmit with an image definition of 7,680 × 4,320 pixels (8K), in 120 Hz ensuring total compatibility with the USB-C interface.
The super MHL adds the ability to switch a current to charge a tablet or smartphone connected to the screen, with a maximum power of 40 W (up to 20V and 2A).

You can also connect a device with a super MHL USB-C port to an HDMI TV with an active super MHL cable.

The return of passive cable

With the arrival of the USB-C connector, there has been a renewed interest in simple and passive cables. Indeed, USB-IF has done the right thing to make and use USB-C cable to HDMI, DisplayPort and MHL.
In addition, the next screens will also be USB-C compatible, so there will not even be a conversion to do : the cable to be used will be USB-C to USB-C.

Dongles New Technologies
Dongles New Technologies


New technologies are also geared towards dongles : more universal, they work at the software level rather than at the hardware level. The best known and most widely used Dongle is Google's Chromecast.
This type of equipment contains a powerful micro-controller that, in addition to the software protection aspect, provides encryption, data security and network-sharing features.

These devices work with virtually all versions of Android and all screens, TVs or video projectors with an HDMI socket.
Indeed, rather than requiring manufacturers of televisions or video projectors to be compatible with a technology like MHL, some have developed this small equipment that already works with the existing fleet.

High-resolution or very high-resolution TV
High-resolution or very high-resolution TV

Recall on televisions HD

HDTV (high-definition television) derives from computer technologies. LCD screens or LED computer monitors are produced with 1080p, 4K or even 8K resolutions.

These high-resolution or very high-resolution screens were designed for computers, and then an interface was added to make them living room televisions.

- 1080p or 720p refer to the resolution of the screen. This number refers to the number of vertical pixels.
- 4K refers to a resolution 4096×2160 pixels i.e. 2160 vertical pixels.

Today's TVs use the following formats :

- 720p 1280 pixels wide by 720 pixels high.
- 1080p 1920 pixels wide by 1080 pixels high.
- 4K 4096 pixels wide by 2160 pixels high.
- 4K Ultra wide TV 5120 pixels wide by 2160 pixels high.
- 8K 7680 pixels wide by 4320 pixels high.

Before HDTV, TV broadcasting had only 480 vertical lines. What is called today 480p. In addition, we have gone from a 4 : 3 image format to a 16 : 9 format. This was done because of the film industry, which has long used a format Widescreen 16:9 for his creations.

Computer screens have grown and have smaller pixels. An original VGA monitor had only 640 x 480 pixels.
Today the video is watched on computer as well as on living room television.
These screens are compatible, only formats and resolution differentiate them.