Select a flash drive. Key Features of USB Flash Drives

Hello my friends. Today we will not consider any schemes of certain designs, the topic for today is the so-called homemade flash drive. Some, of course, may not believe that this is possible at home, and they do it right, since it is quite difficult and it is almost impossible to do it at home without special equipment. But smart people have long come up with a memory card for mobile phones. In stores, you can easily find an adapter with which you can connect a memory card to a computer via a usb port. This adapter only costs $2.

The device works very simply - you just need to put the memory card in a certain place on the adapter, and the adapter itself is made in the form of a USB plug that only needs to be connected to the PC's USB port. For our homemade flash drive, you need to have just such an adapter with a memory card from a mobile phone and one more plug or an appropriate plastic case for USB.

Then we place the adapter in the plug casing and close the cover and see what we got.

Now it looks like a cut off USB plug, but no one will even suspect that there is a memory drive there! Now it's time for the schematics. There are 4 wires, we remove a small part of the insulation from the wires in advance and tin them. Next, we take a couple of brand new parts (it is better to take damaged ones, but so that they look like new ones) and share them with each other. There is no specific circuit here, solder whatever you want, the design should just look like a circuit, of course it will not work! You can use capacitors, resistors, polar and non-polar capacitors and a couple of transistors, as you know, some flash drives have a built-in LED indicator on the back, you can get a simulator of such an indicator so that our homemade flash drive looks believable and does not raise doubts.

To do this, the unpacking of the USB socket and plug is attached to the article, power is supplied through the side channels, which must be connected to our wires, then assemble the simplest flasher circuit for one LED, in which case we have two more free wires to which we can attach a pre-made<блеф>memory storage diagram. So, let's summarize - we got a rather interesting design, when connected to the computer's usb port, the LED will start blinking and it will give outsiders the feeling that a flash drive is connected, but they will be more surprised when the computer notifies that a memory drive is connected to it! Yes, everyone will begin to believe that you are a genius and ask for a diagram of such a simple miracle flash drive. Try to make the details connection scheme as confusing as possible, so that even the master does not suspect what the deception is. Well, that's all, you can see such interesting gizmos in further articles, goodbye friends - Arthur Kasyan (AKA).

Today, flash drives are the most popular external storage media. Unlike optical and magnetic disks (CD / DVD and hard drives, respectively), flash drives are more compact and resistant to mechanical damage. And due to what compactness and stability were achieved? Let's find out!

The first thing to note is that there are no moving mechanical parts inside the flash drive that can be damaged by drops or shocks. This is achieved due to the design - without a protective case, a flash drive is a printed circuit board, to which a USB connector is soldered. Let's look at its components.

Main Components

The components of most flash drives can be divided into basic and additional.

The main ones include:

1. NAND memory chips;
2. controller;
3. quartz resonator.
4. USB connector

NAND memory
The drive works thanks to NAND-memory: semiconductor microcircuits. The chips of such memory, firstly, are very compact, and secondly, they are very capacious: if at first flash drives lost in volume to optical discs familiar at that time, now even Blu-Ray discs exceed in capacity. Such memory, among other things, is also non-volatile, that is, it does not require a power source to store information, unlike RAM chips created using a similar technology.


However, NAND memory has one disadvantage compared to other types of storage devices. The fact is that the service life of these chips is limited by a certain number of rewriting cycles (steps of reading / writing information in cells). On average, the number of read-write cycles is 30,000 (depending on the type of memory chip). It seems like an incredible amount, but it actually equates to about 5 years of heavy use. However, even if the limit is reached, the flash drive can continue to be used, but only for reading data. Also, due to its nature, NAND memory is very vulnerable to electrical surges and electrostatic discharges, so keep it away from sources of such hazards.

Controller
Number 2 in the figure at the beginning of the article is a tiny microcircuit - a controller, a communication tool between flash memory and connected devices (PCs, TVs, car radios, etc.).


A controller (otherwise called a microcontroller) is a miniature primitive computer with its own processor and some amount of RAM used for data caching and service purposes. The procedure for updating the firmware or BIOS means just updating the microcontroller software. As practice shows, the most common failure of flash drives is the failure of the controller.

Quartz resonator
This component is a tiny quartz crystal, which, like in an electronic watch, produces harmonic vibrations of a certain frequency. In flash drives, the resonator is used to communicate between the controller, NAND memory, and additional components.

This part of the flash drive is also at risk of damage, and, unlike problems with the microcontroller, it is almost impossible to solve them on your own. Fortunately, in modern drives, resonators fail relatively rarely.

USB connector
In the vast majority of cases, modern flash drives have a USB 2.0 type A connector, which is focused on receiving and transmitting. The newest drives use USB 3.0 Type A and Type C.

Additional components

In addition to the main components of a flash storage device mentioned above, manufacturers often supply them with optional elements, such as an LED indicator, a write protection switch, and some specific features for certain models.

Led indicator
Many flash drives have a small but fairly bright LED. It is designed to visually display the activity of a flash drive (writing or reading information) or is simply a design element.


This indicator most often does not carry any functional load for the flash drive itself, and is needed, in fact, only for user convenience or for beauty.

Write protect switch
This element is more typical for SD cards, although it is sometimes found on USB storage devices. The latter are often used in a corporate environment as carriers of a variety of information, including important and confidential. To avoid incidents with accidental deletion of such data, manufacturers of flash drives in some models use a protection switch: a resistor that, when connected to the power supply circuit of a storage device, prevents electric current from reaching the memory cells.


When you try to write or delete information from a drive that has protection enabled, the OS will display the following message.

In a similar way, protection is implemented in the so-called USB keys: flash drives that contain security certificates necessary for the correct operation of some specific software.

This element can also break, resulting in an unfortunate situation - the device seems to be operational, but it is impossible to use it. We have material on our site that can help solve this problem.

Unique Components

These include, for example, the presence of Lightning, microUSB or Type-C connectors: flash drives with these are designed for use, including on smartphones and tablets.

How to recover deleted files from flash drive? What is the difference between flash drives and external hard drives? How to recover data?

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Recently, information carriers based on flash memory chips have gained wide popularity. In popularity in our time, they have no equal: memory cards in cameras, cell phones, players, USB flash key fobs, and more recently, SSD drives. Many devices are equipped with memory card slots, such as printers, stationary DVD players, car radios, and many other multimedia devices.

And such popularity is not accidental: in terms of practicality, “flash drives” also have no equal. A large, constantly growing volume, which is already calculated in gigabytes and tens of gigabytes, a fairly high speed, as well as the declared reliability and durability (we will dwell on this issue in more detail within the framework of this article).

First, consider the flash drive device.

Flash memory gets its name from the way it is written and erased.

A typical USB flash drive, as well as most types of memory cards and SSD drives, are arranged as follows:

• the board has microcontroller, which provides a flash drive interface, processes commands and performs memory operations;
• one or more memory chips;
• and their electronic "strapping" of passive elements.

Some memory cards do not have a built-in controller, and are essentially a memory chip packaged in a case.

Let's look at the main components of a flash drive in a little more detail.

flash drive memory chips

All modern flash drives are based on non-volatile NAND memory chips. The abbreviation NAND comes from the phrase NOT-AND (logical function AND-NOT), which underlies the organization of an elementary logical cell on which this memory is built. Elementary memory cells in these microcircuits are combined into pages, and pages into blocks.

With such an organization, access to a separate memory cell is impossible, you can only read the entire page, and erase and rewrite only the whole block. Of the features of such an organization, one can note high speed and high density of placement on a chip.

But there are also disadvantages.

For example, if the power of the device is suddenly turned off while making changes to a certain data block, there is a possibility of data loss in this block, since it could be read into the buffer, erased in the main memory matrix, and the changed block has not yet been written to the memory. This is a common cause of so-called “logical” drive corruption.

It is known that operating systems of the Windows family have a “write-back” mode. This is when data is written to the drive directly without delay, and the file allocation table is stored in RAM, and is updated on the media after a while or when certain events occur.

As a result, quite often there is a situation when, having written data to a USB flash drive, the user immediately removes it from the connector without using the safe shutdown function, which just updates the file allocation tables on the media and “correctly” unmounts it from the system.

As a result, in the best case, the data will be physically present on the drive, but will not be displayed in the file tree, and in the worst case, the logical structure of the drive will be damaged, and the drive may no longer be correctly “detected”. As they say in such cases, "the computer does not see the USB flash drive."

In all such cases, data can be quickly restored by contacting our information recovery center.

The main problem with flash memory is the wear of memory cells.

The fact is that any flash memory has a limited number of rewriting cycles for each cell (from 100,000 to 1,000,000 cycles).

If in a camera or player where the data is not updated too often, such a limitation is not critical, then, for example, when working with databases on a flash drive, this resource can be used up quite quickly, since changes occur very often, as a result of which one and the same blocks of data.

In this regard, it is not recommended to use flash memory for work, constant access to data, as well as for installing an operating system on it, since the resource of such a flash drive will be exhausted very quickly, and the flash drive will become unusable.

Never use a USB flash drive to work in accounting programs!

Flash drive controller

The most complex and mysterious part of a flash drive is, of course, its controller.

Its main functions are working with memory chips (performing paging operations, data fetching, block writing, placing and addressing data in several memory chips, as well as other special functions) and providing an interface to the host device.

When a command is received to read a certain data cell, the controller must determine in which chip this cell is located, in which block of this chip, in which page of the block, and then the actual address of the cell in the page. Since only the entire page can be read, the controller reads it into its buffer, finds the desired cell in it, and sends its contents to the host device.

When a write command is received, the required block is also found, but this time it is not read page by page, but in its entirety. Then the necessary changes are made in the buffer, the block from the microcircuit is completely erased, and the changed block is written again from the controller buffer.

In addition, to equalize the wear of the blocks, the controller periodically reassigns them (in fact, swaps them). As a result, fairly even wear is achieved over write cycles, and the memory chips thus last longer. The controller monitors the status of each block separately, and if any of the blocks has exceeded the allowable number of rewrite cycles, the controller switches to read-only mode - data can be read from it, but it can no longer be written. Such drives are not suitable for further use.

In this case, you should copy the data from the media and replace it.

The controller has a firmware, configuration tables, and some models store tables of wear of memory blocks, as well as a lot of other service information. The variety of controllers is very large, and their versions are simply countless. Concerning, in case of any damage to the controller, it is pointless to look for a replacement to restore information.

To recover in this case, memory chips are soldered, read on special equipment, and the data is collected manually as a mosaic.

Electronic binding is needed to power the microcircuits and match the logic levels. And although there is nothing complicated here, it is not uncommon for this particular electronic harness to fail, especially the power stabilizer. Data recovery in this case depends on the degree of damage: either the electronics are restored directly on the flash drive, and the data is read out in the normal mode, or, as in the case of a burned-out controller, the data is taken directly from the memory chips and collected manually.

Recently, there are flash drives in which the controller, memory and all electronics are packed into one chip. These are monolith flash drives. This design is much more compact than the classical one, but has many disadvantages: less reliability, poorer cooling, and the inability to access the memory chip bypassing the controller.

In the event of a controller failure, or an electronic harness in a similar flash drive, the complexity of data recovery work increases by an order of magnitude.

A question that often arises among potential buyers is which flash drive to choose, and how to choose a flash drive?

Many are guided by famous brands, in the hope that the products of a well-known company will be better and more reliable, but here things are a little different. As a rule, the trademark under which a particular flash drive is produced has nothing to do with the production of the device at all, but only orders a batch of ready-made flash drives with their own logos and packaging, and the product quality does not depend on the trademark in any way.

As a rule, it is impossible to select a flash drive by a specific controller or memory chips - even in flash drives of the same appearance from different batches, different microcircuits can be used.

Therefore, the criteria for choosing a flash drive is extremely subjective.- solid construction, rigid fastening of the USB connector, no moving parts, preferably a metal case (for better cooling and protection from static) and a classic multi-chip architecture.

The easiest way to distinguish a flash drive of a classic design from a single-chip one is by the USB connector - ordinary flash drives have a metal connector, like on any USB cable, single-chip connectors are usually thin, half the size of a port, without a metal part around the perimeter.

As you can see, despite all the pluses, flash drives have enough disadvantages, in the light of which it is not worth trusting flash drives with valuable information in a single copy.

The essence of the problem

After a power failure, accessing the flash drive becomes impossible because the computer either does not respond at all to its connection, or the message “USB device is not recognized” is displayed. USB flash drives are more susceptible to this type of damage because they are powered directly from the USB port and use their own converters to power internal circuits. SD, microSD, CF cards are usually used in photo and video technology. And when connected to a computer, they do not feed directly from it, because intermediate devices are used to connect them - card readers.

Causes

• Incorrect connection of additional USB connectors to the motherboard
• Malfunction of the motherboard or power supply, which led to an increase in voltage at the USB connectors.
• Defective USB extension cables and USB hubs with low-quality power supplies
• Spontaneous failure of flash drive elements

• Complete lack of system response to connecting a flash drive
• "USB Device Unrecognized" Message Appears
• Message about exceeding the permissible current consumption from the USB connector
• The smell of burning from the flash drive.

The impact of this fault on user information depends on the extent of the damage. If only the power circuits of the flash drive fail, this does not affect the user data in any way and they are completely restored. If the controller burns out, then it is necessary to solder the memory and read it on the NAND reader. In this case, the recovery quality is usually good too. But if it breaks directly into the memory chips of a flash drive, then in this case data recovery is usually impossible.

Diagnostic methods

Electrical damage to flash drives is diagnosed in the same way as any electronic device. Burnt-out elements with traces of thermal damage can be seen immediately. The rest is checked by instruments. Security elements (if any) are checked. The voltages supplied to the circuit are checked. Modern production is moving along the path of increasing integration and minimizing the number of individual elements in devices, as well as improving energy efficiency - linear voltage stabilization circuits are being replaced by pulsed ones with high efficiency. Let's see how the circuitry of flash power circuits has changed over time.
On fig. 2 shows the other two flash drives, on completely different controllers. What they have in common is that they contain a minimum of active components (microcircuits) - only controllers and memory chips, the rest of the elements are passive - resistors, capacitors. Those. at least a little, but the cost of production is reduced. On the top flash drive, the controller is U1, on the bottom - U4. Both have a power regulator built into the controller.

Well, the most modern version.

Recovery technique

In the first version, as in Fig. 1 stabilizer U2 takes the whole blow, the rest, as a rule, remains intact. Therefore, it is enough to supply 3.3V power to the desired point in the circuit, connect the USB flash drive to USB and read the data. The only thing that spoils this idyllic picture is that such flash drives are no longer made. The photo shows a Transcend JetFlash 512MB flash drive.

In the second variant in Fig. 2, where a power stabilizer is built into the controller, this is not possible. Here it would be possible to replace the controller, but it is very difficult to find the same one. Because they, even within the same model, differ in firmware, depending on the time of release and the flash memory chips used, which together gives rise to many combinations. The only way to restore such a flash drive is to solder and read the flash memory chips.