Problems when charging various devices via USB often arise when non-standard chargers are used. At the same time, charging occurs rather slowly and incompletely or completely absent.

It should also be said that charging via USB is not possible with all mobile devices. They have this port only for data transfer, and a separate round socket is used for charging.

The output current in computer USB is no more than half an ampere for USB 2.0, and for USB 3.0 – 0.9 A. For a number of devices, this may not be enough for a normal charge.

It happens that you have a charger at your disposal, but it does not charge your gadget (this may be indicated by a message on the display or there will be no charge indication). Such a charger is not supported by your device, and this may be due to the fact that a number of gadgets scan for the presence of a certain voltage on pins 2 and 3 before starting the charging process. For other devices, the presence of a jumper between these pins, as well as their potential, may be important.

Thus, if the device does not support the proposed type of charger, then the charging process will never begin.

In order for the device to start charging from the charger provided to it, it is necessary to provide the necessary voltages on the 2nd and 3rd USB pins. These voltages may also differ for different devices.

Many devices require that pins 2 and 3 have a jumper or resistance element whose value is no more than 200 ohms. Such changes can be made in the USB_AF socket, which is located in your memory. Then it will be possible to charge using a standard Data cable.

The Freelander Typhoon PD10 gadget requires the same connection circuit, but the charge voltage must be at 5.3 V.

If the charger does not have a USB_AF socket, and the cord comes out directly from the charger case, you can solder mini-USB or micro-USB plugs to the cable. Connections must be made as shown in the following picture:

Various Apple products have this connection option:

In the absence of a 200 kOhm resistance element on pins 4 and 5, Motorola devices cannot carry out a full charge.

To charge the Samsung Galaxy, you need a jumper on pins 2 and 3, as well as a 200 kOhm resistor element on pins 4 and 5.

It is recommended to fully charge the Samsung Galaxy Tab in gentle mode using two resistors with a nominal value of 33 kOhm and 10 kOhm, as shown in the picture below:

A device such as E-ten can be charged by any charger, but only on the condition that pins 4 and 5 are connected by a jumper.

This scheme is implemented in the USB-OTG cable. But in this case, you need to use an additional male-to-male USB adapter.

The Ginzzu GR-4415U universal charger and other similar devices have sockets with different resistor connections for charging iPhone/Apple and Samsung/HTC devices. The pinout of these ports looks like this:

To charge your Garmin navigator, you need the same cable with a jumper on pins 4 and 5. But in this case, the device cannot charge while in use. In order for the navigator to be recharged, it is necessary to replace the jumper with a resistor rated 18 kOhm.

Tablets usually require 1-1.5A to charge, but as mentioned earlier, USB ports will not be able to charge them properly as USB 3.0 will only output 900mA maximum.

Some tablet models have a round coaxial socket for charging. In this case, the positive pin of the mini-USB/micro-USB socket does not have a connection to the battery charge controller. According to some users of such tablets, if you connect the plus from the USB socket to the plus of the coaxial socket with a jumper, charging can be carried out via USB.

You can also make an adapter for connecting to a coaxial socket, as shown in the figure below:

Here are the jumper diagrams indicating the voltage and resistor values:

As a result, in order to charge various gadgets from non-native chargers, you need to make sure that the charging produces a voltage of 5 V and a current of at least 500 mA, and make changes to the USB socket or plug according to the requirements of your device.

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Universal Serial Bus or USB for short

Universal Serial Bus, or USB for short, is actively used in modern digital computer technology. Currently, USB 1.1 and USB 2.0 versions are used. USB 2.0 version is forward and backward compatible with USB 1.1. In other words, devices with USB 2.0 work successfully with computers equipped with USB 1.1 and vice versa. All USB 1.1 and USB 2.0 cables and connectors are the same.

USB

USB(short for the English term Universal Serial Bus - "universal serial bus", pronounced "u-es-bee") - a serial data transfer interface for low- and medium-speed peripheral devices in digital computer technology.

Universal Serial Bus (USB) - “universal serial bus” has its own special designation, i.e. its own special graphic symbol.

USB symbol

The USB symbol is represented by four geometric shapes: a large circle, a small circle, a triangle and a square, located at the ends of a tree-like block diagram. The USB symbol can be applied to equipment housings, connectors and devices.

USB 2.0 differs from USB 1.1 by introducing the Hi-speed mode. USB 2.0 High Speed ​​has its own logo.

USB 2.0 High Speed ​​logo printed on the Card Reader

Fig.1. Example of a USB cable. USB symbols on the connectors are clearly visible

To connect peripheral devices to the USB bus, a special four-core cable is used, with two wires (twisted pair) in the differential connection used for data exchange, and the other two for powering the peripheral device, see Fig. 2.

Fig.2. USB cable with main parameters marked

USB allows you to connect peripheral devices without its own power source (the maximum current consumed by the device via the USB bus power lines should not exceed 500 mA) see Fig. 3.

Fig.3. USB has its own power lines, this allows you to connect peripheral
devices without their own source, for example, an external hard drive

One USB bus controller allows you to connect up to 127 devices in a star topology, including hubs. On one USB bus there can be up to 127 devices and up to 5 levels of cascading hubs, not counting the root one.

Thanks to its versatility, USB is gradually replacing ports such as COM and LPT. Fortunately, manufacturers of printers and scanners provide for the operation of their devices with USB and provide the appropriate connectors. In addition, new non-traditional USB devices are emerging, such as compact MP3 players. Connecting to USB allows you not only to copy music files to such players, but also charges the built-in battery, which ensures autonomous operation of the player.

USB cable

The USB cable is four-core braided, it consists of 4 copper conductors - 2 power conductors and 2 conductors for data transmission in the form of a twisted pair, plus a grounded braid (screen) see Fig. 4.

Fig.4. USB cable. The different connectors at the ends of the cable are clearly visible.
This is because USB cables are oriented

USB cables are oriented; for this purpose, USB cables are equipped with different connectors for connecting “to the device” and “to the host”. It is possible to implement a USB device without a cable, with a “to-host” tip built into the housing. An example of such a device is a flash memory card or USB modem. It is also possible to permanently integrate the cable into the device; an example would be a computer mouse, see Fig. 5. (the standard prohibits this for full and high speed devices, but manufacturers violate it). There are (although prohibited by the standard) passive USB extenders that have connectors “from the host” and “to the host”.

Fig.5. One-piece integration of the USB cable into the device.
Example, a computer mouse has a built-in USB cable

USB 1.1 and USB 2.0. Connectors, cables and wiring

USB connector wiring diagram (cable and device)

USB connector wiring diagram (cable and device)

USB signals are transmitted over two wires (twisted pair) of a shielded four-core cable.

VBUS – voltage +5 Volts of the power circuit, GND – contact for connecting the “housing” of the power circuit. The maximum current consumed by the device through the USB bus power lines should not exceed 500 mA. Data is transmitted through the D- and D+ pins of the USB connector. Differential data transfer method is the main one for USB.

The USB 2.0 cable is shielded to ensure higher data transfer speeds. It is also four-core, but braided and consists of 4 copper conductors in colored insulation. Two power conductors and 2 data conductors in the form of twisted pair. The wires are placed in a grounded braid (screen).

USB cable connectors

For the USB cable, special USB connectors are used. The USB cable is directional, therefore, for proper connection, the USB connectors have different configurations. There are two types of USB connectors: Type A (see Fig. 7. and Fig. 8.) and Type B (see Fig. 9., Fig. 10. and Fig. 11).

Fig.7. Regular USB cable connector Type A

In accordance with the 1.0 specification, USB Type A connectors are used for connection “to the host”, i.e. installed on the controller or USB hub side.

Fig.8. “Branded” USB cable connector Type A (with the name of the manufacturer)

In accordance with the 1.0 specification, USB Type B connectors are used for connection “to the device”, i.e. for connecting peripheral devices.

Fig.9. Regular USB cable connector Type B. This connector is suitable for, for example,
to connect a printer

Fig. 10. Regular USB mini cable connector Type B

Fig. 11. Micro USB cable connector Type B.
In the figure below the USB symbol you can clearly see the designation Type B

In Fig.12. and Fig.13. USB cables shown. These USB cables are equipped with a regular Type A USB cable connector and a Type B USB mini cable connector.

Fig. 12. USB cables are equipped with a regular USB cable connector

B

Fig. 13. USB cables are equipped with a regular USB cable connector
Type A (in the picture on the left) and a USB mini cable connector
Type B (shown on the right). Type B is designated as b

Fig. 14. USB cable equipped with a miniature connector called micro USB

USB supports hot (power on) plugging and unplugging of devices. This is achieved by increasing the length of the grounding contact of the connector in relation to the signal contacts, see Fig. 15. When a USB connector is connected, the grounding contacts are closed first, the potentials of the bodies of the two devices are equalized, and further connection of the signal conductors does not lead to overvoltages, even if the devices are powered from different phases of a three-phase power network.

Fig. 15. Ground Pin Length

The length of the grounding contact (in the figure, pin 4 GND at the top) of the connector is increased in relation to the signal (in the figure, pin 3 D+ at the bottom) contacts. The upper contact is longer than the lower one. This allows you to connect and disconnect devices without turning off the power (so-called “hot plugging and unplugging”)

The mating parts of the USB connectors are located on peripheral devices connected via USB, see Fig. 16. and Fig.17.

Fig. 16. USB cable connector. The USB symbol is clearly visible

Fig. 17. USB mini Type B cable connector

Fig. 18. Comparison of USB connector sizes.

A regular USB cable connector Type A (in the picture on the left), a USB mini cable connector Type B (in the picture in the center) and a USB micro cable connector Type B (in the picture on the right). Type B is designated as B

It has been developed since 1994, and the development team consisted of engineers from leading companies in the field of IT technologies - Microsoft, Apple, Intel and others. During the research process, one goal was pursued - to find a universal port that could be used for most devices.

Thus, users were provided with a USB connector, which was almost immediately supported by various developers and began to be actively used in a variety of devices, from personal computers to mobile gadgets. However, it so happened that cables with such connectors could not be used everywhere, and they themselves were different, and therefore some require unsoldering a mini-USB connector in order to make the appropriate adapter.

However, few people know how this procedure should be carried out correctly.

Concepts you need to know

Wiring a USB connector begins with learning the basic concepts:

• VCC - positive potential contact For modern USB cables, the indicator of this contact is +5 Volts, it is worth noting that in radioelectric circuits this abbreviation fully corresponds to the supply voltage of PNP, as well as NPN transistors.
• GND - negative potential contact of the power supply. In modern equipment, including various models of motherboards, this device is connected by a housing in order to provide effective protection from static electricity or any external sources of electromagnetic interference.
• D- - information contact having zero potential, regarding which information is broadcast.
• D+ is an information contact that has a logical unit. This contact is used to broadcast information from the host to the device or vice versa. At the physical level, this process represents the transmission of rectangular pulses with a positive charge, while the pulses have different amplitudes and duty cycles.
• Male is the plug of this connector, which is often called “male” among modern users who wire the USB connector for a mouse and other devices.
• Female - the socket into which the plug is inserted. Users are called "mother".
• RX - receiving information.
• TX - information transfer.

USB-OTG

OTG is a method of connecting two peripheral devices via a USB cable without the need for a computer. Also, such a pinout of a micro-USB connector is often called a USB host in professional circles. In other words, a flash drive or some kind of hard drive can thus be directly connected to a tablet or mobile phone in the same way as to a full-fledged personal computer.

In addition, you can connect mice or keyboards to gadgets, if they support the ability to use them. Cameras and other gadgets are often connected to printers in this way.

What limitations does it have?

The limitations that this type of micro-USB connector has are the following:

For example, if we are talking about connecting some kind of USB flash drive to the phone, then in this case the “USB_AF-USB_AM_micro” adapter is most often used. In this case, a flash drive is inserted into the connector, while the plug is connected to the mobile phone.

Cable Feature

The main feature that distinguishes the wiring of a USB connector in the OTG format is that in the plug, pin 4 must be connected to pin 5. In a standard data cable, nothing is soldered to this pin at all, but this plug is called USB-BM micro. It is for this reason that you need to get to the fourth contact, and then use a jumper to connect it to the GND wire. After this procedure, the plug will be renamed USB-AM micro. It is the presence of a jumper between these contacts in the plug that allows the device to determine that some kind of peripheral device is about to be connected to it. If the device does not see this jumper, it will act as a passive device, and any flash drives connected to it will simply be completely ignored.

How are devices identified?

Many people believe that when connecting in OTG mode, both devices fully automatically determine which of them will be the host and which will be the slave. In fact, in this case, only the user determines who exactly in this case will be the master, since in which device the plug equipped with a jumper between 4 and 5 contacts will be inserted, then of them will be the host.

How to make it?

Through the translucent insulation you can see several multi-colored wires. You will need to melt the insulation near the black wire, then solder one end of the jumper to the GND pin. On the opposite side you can see a white wire, as well as an unused pin. In this case, we need to melt the insulation near the unused contact, and then solder the second end of the jumper to it.

It is worth noting that the wiring diagram for a micro USB connector is much simpler.

The unraveled plug, which you equipped with a jumper, will need to be insulated, for which a specialized heat-shrinkable tube is used. After this, you will just need to take the “mother” from the extension cord and solder it to our color-matched plug. If the cables are shielded, then you will also need to connect the shields, among other things.

Can it be charged?

If peripherals are connected to the device via OTG, then it will have to power it, which can significantly reduce the overall operating time of the device from the built-in battery. In this regard, many people wonder whether it is possible to recharge such a device through an external source. This is possible, but this requires support for a special mode in the device, as well as a separate wiring of the USB connector for charging.

In fact, the charging mode is most often provided by modern gadget developers, but not everyone allows such a procedure. It should be noted that to switch to this charging mode, a separate USB connector wiring diagram must be used, in which the contacts are closed through a separate resistor.

The USB connector appeared twenty years ago and was originally intended for use in household appliances. Currently, it has become quite popular also in professional equipment. However, its “household” roots are clearly evident in the fact that all popular gadgets without exception are equipped with this type of detachable connector.

The original version of the connector had dimensions that were not quite suitable for installing its sockets in portable pocket-sized devices. To eliminate this drawback, miniUSB and microUSB variants were created, which made it possible to implement the basic functions of the connector and at the same time differed favorably from the prototype with noticeably better weight and size characteristics.

Characteristics of the microUSB connector

The microUSB connector contains five contacts, each of which has an insulated wire soldered to it. The correct orientation of the plug when connected to an outlet is determined by the use of characteristic smoothed bevels on one of the upper edges of the shielding skirt. The pins of the connector plug are designated by numbers from 1 to 5 with natural numbering from right to left as shown in the figure. Wiring micro usb connector and the purpose of its individual contacts are given in the table.

Micro USB pinout by color

The braided shielding of a cable is also considered a wire. It is not output to a separate contact.

Wiring out the micro usb charging connector

Connector repair and cable manufacturing

The good performance properties of the cable and instrument part of the micro USB connector, combined with the low cost of the connecting cable and its wide distribution, lead to the fact that repairs to this accessory are carried out relatively rarely. However, if it is installed, a new nest, due to its well-thought-out design, is not a big problem, even despite its rather miniature size. Among the features, you should pay attention to the accuracy and feasibility of additional protection of the soldering area, for example, with non-conductive varnish.

USB (Universal Serial Bus- “universal serial bus”) - a serial data transfer interface for medium-speed and low-speed peripheral devices. A 4-wire cable is used for connection, with two wires used to receive and transmit data, and 2 wires to power the peripheral device. Thanks to the built-in USB power lines allows you to connect peripheral devices without its own power supply.

USB Basics

USB cable consists of 4 copper conductors - 2 power conductors and 2 data conductors in twisted pair, and a grounded braid (screen).USB cables have physically different tips “to the device” and “to the host”. It is possible to implement a USB device without a cable, with a “to-host” tip built into the housing. It is also possible to permanently integrate the cable into the device(for example, USB keyboard, Web camera, USB mouse), although the standard prohibits this for full and high speed devices.

USB bus strictly oriented, i.e. it has the concept of “main device” (host, also known as a USB controller, usually built into the south bridge chip on the motherboard) and “peripheral devices”.

Devices can receive +5 V power from the bus, but may also require an external power supply. A standby mode is also supported for devices and splitters upon command from the bus, removing the main power while maintaining standby power and turning it on upon command from the bus.

USB supportsHot plugging and unplugging of devices. This is possible due to the increase in the length of the grounding contact conductor in relation to the signal ones. When connected USB connector are the first to close grounding contacts, the potentials of the housings of the two devices become equal and further connection of the signal conductors does not lead to overvoltages, even if the devices are powered from different phases of a three-phase power network.

At the logical level, a USB device supports data transfer and reception transactions. Each packet of each transaction contains a number endpoint on the device. When a device is connected, drivers in the OS kernel read a list of endpoints from the device and create control data structures to communicate with each endpoint on the device. The collection of endpoints and data structures in the OS kernel is called pipe.

Endpoints, and therefore channels, belong to one of 4 classes:

• continuous (bulk),
• manager (control),
• isochronous (isoch),
• interrupt.

Low speed devices such as a mouse cannot have isochronous and flow channels.

Control channel designed for exchanging short question-answer packets with the device. Any device has control channel 0, which allows the OS software to read brief information about the device, including manufacturer and model codes used to select a driver, and a list of other endpoints.

Interrupt channel allows you to deliver short packets in both directions, without receiving a response/confirmation, but with a guarantee of delivery time - the packet will be delivered no later than in N milliseconds. For example, used in input devices (keyboards, mice or joysticks).

Isochronous channel allows you to deliver packets without a guarantee of delivery and without replies/confirmations, but with a guaranteed delivery speed of N packets per bus period (1 KHz for low and full speed, 8 KHz for high speed). Used to transmit audio and video information.

Flow channel provides a guarantee of delivery of each packet, supports automatic suspension of data transmission due to device reluctance (buffer overflow or underrun), but does not guarantee delivery speed and delay. Used, for example, in printers and scanners.

Bus time is divided into periods, at the beginning of the period the controller transmits the “beginning of period” packet to the entire bus. Then, during the period, interrupt packets are transmitted, then isochronous ones in the required quantity; for the remaining time in the period, control packets are transmitted, and lastly, stream packets.

Active side of the bus is always the controller, the transfer of a data packet from the device to the controller is implemented as a short question from the controller and a long response from the device containing data. The packet movement schedule for each bus period is created jointly by the controller hardware and driver software; for this, many controllers use Direct Memory Access DMA (Direct Memory Access) - mode of data exchange between devices or between the device and the main memory, without the participation of the Central Processor (CPU). As a result, the transfer speed is increased since data is not sent back and forth to the CPU.

The packet size for an endpoint is a constant built into the device's endpoint table and cannot be changed. It is selected by the device developer from among those supported by the USB standard.

USB Specifications

Features, advantages and disadvantages of USB:

• High transfer speed (full-speed signaling bit rate) - 12 Mb/s;
• The maximum cable length for high transfer speed is 5 m;
• Low-speed signaling bit rate - 1.5 Mb/s;
• The maximum cable length for low communication speed is 3 m;
• Maximum connected devices (including multipliers) - 127;
• It is possible to connect devices with different baud rates;
• There is no need to install additional elements such as terminators;
• Supply voltage for peripheral devices - 5 V;
• The maximum current consumption per device is 500 mA.

USB signals are transmitted over two wires of a shielded 4-wire cable.

USB 1.0 and USB 2.0 connector pinout

Type A		Type B
Fork (on cable)	Socket (on the computer)	Fork (on cable)	Socket (on peripheral device)

Names and functional assignments of USB 1.0 and USB 2.0 pins

Data 4 GND Ground (body)

Disadvantages of USB 2.0

At least the maximum USB 2.0 data transfer rate is 480 Mbit/s (60 MB/s), in real life it is unrealistic to achieve such speeds (~33.5 MB/s in practice). This is due to the large delays on the USB bus between the request for data transfer and the actual start of the transfer. For example, FireWire, although it has a lower peak throughput of 400 Mbps, which is 80 Mbps (10 MB/s) less than USB 2.0, actually allows for greater data transfer throughput to hard drives and other storage devices. In this regard, various mobile drives have long been limited by the insufficient practical bandwidth of USB 2.0.