The main task of the USB interface on the mobile phone is to charge and connect the PC to transmit data. Can you think of other functions? Yes, it can also connect USB small fans, small lamps and other peripherals. However, do you think all mobile phones have the same experience and effect when implementing these functions?

Boy, you are naive!

Charging speed has little to do with the interface

Mobile phone charging relies on USB interface, but at this stage, Android mobile phone USB is nothing more than micro USB and type-c. why are the charging speeds of different brands of mobile phones very different?

In fact, in general, the USB interface of mobile phones has little to do with the charging speed. For example, the current popular fast charging technologies such as Qualcomm QC and MediaTek PEP rely on the power management chip integrated with the processor SOC, which can charge normally at 5V or quickly at 9V or 12V. These chips the final say, and then judge the amount of current to be supplied by judging the resistance between the two wires.

Of course, there are also unusual cases. For example, the vooc flash charging of oppo adopts the fast charging strategy of low voltage and high current, while the micro USB used in oppo mobile phones is inherently unable to carry too much current. Therefore, oppo had to adopt an improved micro USB interface, adding two pins on the basis of the standard micro USB to identify and transmit greater current.

We all know that the dash of Yijia mobile phone 3 comes from vooc. However, since Yijia mobile phone 3 uses USB type-C interface, and type-C can naturally carry greater current and voltage, there is no need to physically transform the interface.

In the future when type-C will unify the mobile interface Jianghu, do you want to judge the type and speed of fast charging technology through the interface? The answer can only be: no!

Why type-C failed to bring USB3.0

The question is, USB type-C has been under the banner of “usb3.1” since its birth. Why is the USB transmission speed of mobile phones equipped with this interface still dominated by USB2.0?

Before answering this question, let’s talk about USB type-C briefly. USB type-C is only a form of physical interface, and its special functions such as USB3.0, usb3.1 or lightning 3 are “optional”. In the Android mobile phone field, 99% of mobile phones have chosen the default USB2.0, and only a few models have adopted USB3.0.

The reason is very helpless. During data transmission, USB3.0 will interfere with mobile phone signals (including 4G network and Wi Fi) and wireless keyboard and mouse (including 2.4G, 5g and Bluetooth). However, there is no effective solution to this problem for many years. This can be seen from Samsung’s attitude towards USB3.0:

Galaxy note 3 used to focus on USB3.0, but many users reported that when connecting to the computer to transfer files, the 4G signal of the mobile phone would suddenly be interrupted and automatically switch to 3g/2g mode. As a result, the problem of signal interference caused by USB3.0 has attracted the attention of the industry, and Samsung has also given up its support for USB3.0 in subsequent new products.

By the way, Android phones that currently support USB3.0 also shield this function by default, but transmit data at the speed of USB2.0. If you want to switch to USB3.0, a prompt that may affect the signal quality will pop up. So, don’t get too tangled about why Android phones use type-C but don’t provide USB3.0 speed.

Why can type-C be used as a headphone hole?

Nowadays, many Android phones represented by LETV and moto have canceled the 3.5mm earphone hole, and listening to songs and charging all rely on the new type-c. Is this a very high-end technology?

Boy, don’t be surprised! As the ancestor of mobile phone USB interface, it is not new to use it to connect headphones as early as the Mini USB interface era. For example, Motorola L7 and HTC Touch Diamond used Mini USB as the representative of headphone interface more than ten years ago.

The reason is very simple. Including USB type-C, type-A (standard USB interface) and type-B (Mini USB, micro USB) USB interfaces all support the transmission of audio signals. Since Android 5.0, Google has integrated a standard USB audio driver library into the system, which can transmit audio signals through USB. Therefore, theoretically, as long as the system version is above Android 5.0 and the mobile phone is equipped with a type-C interface, the headset with a type-C interface can be directly used.

Is reverse charging really high-end?

Nowadays, many mobile phones equipped with large batteries are mainly supporting the function of reverse charging, that is, they claim to play the role of a power bank to charge other mobile phones. Is this feature very high-end?

In fact, for all mobile phones that support OTG, the biggest feature is that you can charge another mobile phone when you connect it with an OTG cable. Therefore, this reverse charging capability is supported by almost all mobile phones. It’s just that many mobile phones don’t have enough batteries. It’s just that they can’t play the role of a power bank.

So why can all mobile phones that support OTG be recharged in reverse?

OTG should be a feature of Android phones. It can be used to connect external keyboard, mouse, U disk, and peripheral devices such as USB Fan and USB small desk lamp.

For OTG function, it is very important whether the mobile phone USB interface is equipped with a 5V boost module. In the early stage, many middle – and low-end mobile phones will castrate the boost module, so it is physically impossible to support OTG.

OTG cable with bifurcated head, one end can be connected to mobile phone, and the other end can be connected to charger

In addition, although some products are equipped with boost modules, the codes related to OTG are deleted at the system level, which belongs to software shielding OTG. If your mobile phone unfortunately belongs to the above type, you can use the OTG cable of the DC5V power supply (to obtain additional power while connecting to the mobile phone and simulate the 5V boost module) and modify the system/etc/vold The mode curve of fstab code obtains OTG function.

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