pinout usb to com. Do-it-yourself USB-COM adapter: diagram, device and recommendations. Changing the COM port number

A COM USB adapter is a device that allows a computer to connect to peripheral equipment. Today, modern models of system units sometimes lack very important outputs. As a result, the user is limited in their own capabilities.

Thus, only an adapter (adapter) can help the user. It should be noted that these devices differ in the type of connectors. It should also be noted that making them at home is quite simple. True, it is important to first familiarize yourself with their device.

Scheme of an ordinary adapter The USB-COM scheme consists of the following elements:

- port;
- modulator;
- converter;
- resistor.

Sometimes an amplifier can be additionally placed on the board. Often, wired models are selected in this case. In this case, resistors are used exclusively of an open type. This is necessary to increase the maximum frequency of the equipment. As a result, the signal response time will be approximately 20 ms. In addition, the bandwidth of the device must be taken into account. To increase this parameter, most experts advise using only two-way modulators.

Models type A standard

Creating a USB-COM type A adapter yourself at home is quite simple. It is advisable to select a chip in the PP21 type. To stabilize the process in the device, a converter is used. To ensure the normal operation of the model, a high-quality modulator is also needed. In this case, it should be selected only low-frequency type.

This makes it possible to keep the signal response parameter at 30 ms. To ensure better current conductivity, experts recommend using low power transistors. At the same time, they must withstand the maximum voltage at around 3V. It is worth noting that the presented adapters are perfect for various kinds of receivers. It is possible to additionally connect radio receivers with SR101 connectors to them.

Type A mini models

The presented devices can support most known formats. True, they cannot be folded without converters. As an addition, you should choose a microcircuit of the PP22 series. You only need to place three transistors. Two of them must be placed near the converter. In this case, the modulator should be selected as a pulse type. As for the signal response speed, in this case, its average indicator is at the level of 30 ms. To ensure stable operation of the peripheral device, this value is quite enough.

The cord should be fixed on the back of the chip. The main thing is not to touch the modulator during the soldering process. In addition, transistors must be kept clean. Thanks to the frequency amplification stage, the coupling of the circuits is ensured. As a rule, this parameter varies within 12 Hz. To increase the conductivity of the current, some experts recommend the use of amplifiers. The connector for the device is connected last. The driver for the USB-COM adapter must be selected separately.

Type A micro models

Creating a USB-COM type A micro adapter with your own hands is more difficult than the device described above. As a rule, the reason for this is the presence of a non-standard port. It is worth noting that the throughput for it should be quite high. In this case, the signal response parameter must be at least 20 ms. It is also necessary to pay due attention to the search for a converter.

To increase the clock frequency in the device, most users choose their symmetrical type. Transistors in this case are selected in an open modification store. As a rule, the average voltage that they are able to withstand is 3A. As another option, you can pay attention to the combined subspecies. This makes it possible to eventually make the signal response speed higher.

Type B adapter standard

This USB-COM adapter cable is designed for devices that are equipped with an RSR21 connector. First, it is recommended to purchase a modulator in the store. In this case, you can opt for a stepped analogue. True, it must be borne in mind that its bandwidth is quite low. In addition, there may be some problems with overlapping paths in the future. To solve this problem, it is worth using oscillatory modulators.

It should be noted that they are quite expensive. However, the test results prove that oscillatory modulators justify their cost in terms of the quality of work. Take at least the fact that they have copper contacts, which ensures high current conductivity. In addition, good work with a PP20 chip can be attributed to the number of advantages. The port is set last. It should be noted that the cord for it is purchased separately.

Adapter type B mini

The COM USB adapter is assembled using a PP220 chip. In this case, the converter must be selected with a chromatic resistor. As a supplement, it is worth using a high quality modulator. To increase the signal response speed, most experts recommend using open-type transistors.

True, in this case, the bandwidth of the equipment is significantly reduced. As a result, there may be a problem installing the device driver. A trigger is additionally mounted on the USB-COM adapter. He in the system is responsible for conjugation of contours. This process is carried out in a grid triode. It should be noted that this significantly increases the frequency gain. It is worth noting that the port for the adapter is used without a selector.

Type B micro model

Adapters of this type are assembled quite simply. It should be immediately noted that they are currently very popular. The presented adapters are suitable for all devices where there is an RSR 23 type port. The converters are selected for the chip only of the pulse type. It is worth noting that it is desirable to use standard transistors.

True, some experts prefer open-type analogues. In this case, the bandwidth parameter will depend on the type of amplifier. When using a low-frequency modification, problems with the equipment cannot be avoided. Also, longitudinal modifications can significantly increase the current permeability parameter. The cord in this case is soldered to the convection outlet of the microcircuit.

How to choose a model in the store?

Devices with an RSR21 type port require the selection of an RF adapter. The minimum load that it must withstand is 3 A. It is worth noting that the copper of the conductors must be oxygen-free. Only then can you count on good equipment bandwidth. The adapter must support Dolby and True digital formats.

As for the video system, it needs to work with 720p. In most cases, amplifiers in devices are installed contactless. True, some models are equipped with cheaper analog modifications. The outer shell must be made of PVC. The response speed of the signal reaches an average of about 30 ms. Such an adapter, which is of high quality, can be purchased for approximately 2500 rubles.

Specifications USB mini 4P

The presented USB-COM adapter (adapter) differs from others in that the modulator in it is of a double-sided type. This allows for good throughput. This model is ideal for audio devices. In this case, an intermediate traverse is installed. To stabilize the signal, a high-frequency amplifier is used in the device. The signal response speed is approximately 25 ms. On average, the equipment frequency indicator is at the level of 23 Hz. A small reflector is used to correct the current in the adapter.

Model USB 1394B

Devices of this type have a sufficiently high signal response speed, which is their undeniable advantage. The converter here is used low-frequency. It is worth noting that the modulator in this case is installed with a limiting frequency, which is at the level of 23 Hz. This makes it possible to quickly normalize the input voltage. Major formats are supported by installing the device driver.

This adapter uses a pulse-type amplifier. High throughput is possible by increasing the generation parameter. Among the disadvantages of the presented device is the low overlap range. This causes frequent conflicts with the system in the process of connecting peripherals. It is worth noting that the model has a PP19 series chip. This intermediate frequency parameter does not exceed 30 Hz.

USB device TDK

The USB-COM adapter is ideal for connecting receivers with a RSR30 type port to a computer. In the presented case, a high sensitivity transducer is used. It should be noted that the microcircuit is mounted meridional. The modulator is connected with an operating frequency of about 28 Hz. High-quality transistors make the bandwidth in the equipment high. It should be noted that the deviation of the transducer is observed quite rarely. True, the minuses of this adapter are still present. They consist, first of all, in wave distortion. As a result, device synchronization can take a huge amount of time from the user.

USB-COM RS232

This adapter has found its application when connecting devices with RSR21 type ports. In this case, you should pay attention to the high quality of the modulator. The microcircuit here is used type PP21. Transistors are installed analog type. The device does not have a high throughput. True, the signal response speed parameter of this adapter is at around 30 ms. As a rule, this was achieved by installing a powerful converter.

It is able to maintain the operating frequency in the system at 23 Hz. This adapter requires the use of copper contacts. All major formats are supported. The driver for this adapter can be selected from the manufacturer. The outer shell of the device is completely made of PVC. The limit frequency parameter reaches 30 Hz. Thus, the bandwidth of the device is quite high.

Modification USB MINI8M

The presented adapter is actively used in the operation of devices, the connector of which is the RSR26 series. Also, these models are often used to connect receivers to personal computers. As an additional modification, it is possible to install the device in laptops. The dimensions of the equipment are quite compact. The manufacturer has provided coaxial type outputs on the microcircuit. The sensitivity of the presented model does not differ from other devices.

It should also be noted that the operating frequency parameter is at around 21 Hz. Unlike the previous options, in this case, the conductivity of the resistors is much inferior. She is not very tall. As a result, the response time of the signal is on average 20 ms. The intermediate frequency index of the model reaches 33 Hz. It should be noted that thermo-optical modulators are used here. Due to this, wave distortion occurs quite rarely. The presented adapters are often exposed to high temperatures. Thus, they can only be used up to 40 degrees.

Parameters of USB MINI8P

The presented adapter is often installed under various receivers. The value of the operating frequency is 25 Hz. As for the signal response speed, it is at the level of 40 ms. In this case, a non-chromatic type converter is involved. As provided by the manufacturer. The disadvantage is the poor throughput.

True, it is able to withstand a load of approximately 3 A. This affects the stability of the work, which is at a good level. Thus, the transistors in the device burn out quite rarely. Also among the disadvantages is a sharp increase in the clock frequency. This is due to the modulator being out of sync.

Devices with a connector on the controller USB-COM device equipped with a connector on the controller is now considered fairly well known. For him, completely different microcircuits are selected. Usually in this case, low-frequency converters are installed. This is due to the fact that the signal response speed of the models is quite good. Modulators for adapters of the presented type are used only meridional. This leads to an increase in the limiting frequency up to 30 Hz. Although, it is possible to control the stability of the device if you install an amplifier on the model.

Models with connector for peripheral equipment

Adapters that have ports on a peripheral device are not particularly in demand today. It is worth noting that they are completely unsuitable for laptops. As additions, microcircuits can only be used from the PP13 series. As a result, there is a possibility of various problems. First of all, it is necessary to note the low intermediate frequency parameter, which is at the level of 10 Hz.

This is due to the lack of an input resistor on the board. In addition, problems can arise due to a sharp drop in voltage. This happens at the moment when the load on the converter becomes higher than 3 A. True, despite all the above disadvantages, adapters with a connector on a peripheral device are quite useful, especially when it comes to connecting equipment with an RSR24 output.

The article examined the main types of adapters. This information may be helpful when choosing a COM USB adapter.

You will need

• - computer with internet access
• - browser
• - system administration skills
• - Advanced Virtual COM Port
• - USB Serial Converter or Virtual Null Mode

Instruction

Download and install the Advanced Virtual COM Port program. To do this, open a browser and follow the link http://www.advancedvirtualcomport.com/files/AdvancedVirtualComPort.zip. This program includes network and local functions of the virtual COM port. It can virtual port and join it via virtual modem cable, via network or . These, created in the program, look the same as real ones. They work in a similar way. Run the program, follow the procedure for creating a port: click the "create port" button, select the source of the port being created. Follow the instructions of the program. Next, go to the "Control Panel", select "Device Manager", there follow the appearance of a new port in the list.

Download the virtual port driver to set the virtual com port from the site http://com0com.sourceforge.net/. Unpack the archive with the driver into a folder, connect the USB cable to the computer. The other end of the cable, where there are two DB-9 connectors, do not connect anywhere. Next, the hardware will be installed automatically. Select the option "search for a suitable driver for the device", specifying its location. Next, click the "Browse" button and select the downloaded driver. In the next window, click the "Finish" button. After installing the USB Serial Converter, the Serial Port Setup Wizard will start. Repeat the hardware installation procedure using the Found New Hardware Wizard. Restart your computer to make a virtual com port. Go to "Control Panel", "System", click "Device Manager" and track the appearance of a new port.

Download and install Virtual Null Mode. Creating a virtual com port with this program is a fairly simple procedure. After installing the program, the program will prompt you to create a new device, select "Yes", then select the port numbers, click the "OK" button in the program window and in the dialog box. Next, the program will install virtual ports on the computer. Reboot your PC, go to "Device Manager" and check for new ports.

Sources:

• virtual usb port
• Disabling the use of virtual COM ports in Windows

The virtual port is intended for connection to the same port of several installed applications. To do this, copies of the port are created through which data is sent from applications to the real port and the attached device.

You will need

• - access to the Internet;
• - programming skills.

Instruction

Go to http://www.advancedvirtualcomport.com. Go to the file download section and select the Advanced Virtual COM Por program. This application is designed to configure a virtual port and enable its network and local functions. It creates a virtual port and connects it to the modem via a virtual cable to access the network or the internet.

Download the installation file to your computer anywhere. Launch the Advanced Virtual COM Por program and select the "Create Port" option. Next, follow the application's instructions to set the virtual port.

Download the USB Serial Converter driver from http://comocom.sourceforge.net/ to install the virtual port. Unpack the archive with the utility and connect the USB cable to the computer. Leave the other side of the cable free, i.e. don't connect anywhere. This will then automatically install the hardware.

Click on the "Search for a suitable driver" button and specify the location of the downloaded folder. Click the Done button. The virtual port setup wizard will start. When finished, restart your computer and check for a new port.

Install the Virtual Null Modem program on your personal computer, which will easily help you create a virtual port. You can download the application from http://www.virtual-null-modem.com/. After the installation is complete, a window will appear asking you to create a virtual port. Click the Yes button and enter the port number. Restart your computer after installing the new port.

Check the appearance of the virtual port. To do this, click on the "Start" button and go to the "Control Panel" section. Select the "Device Manager" menu and read the list of ports, one of them will be virtual. You can also access Device Manager by right-clicking on the My Computer shortcut and selecting Manage.

Related videos

When working with a PC, there are times when several applications are installed on your system that require a com port to work. However, the number of these ports is not always equal to the number of such applications. Therefore, if there is a shortage of these devices, the OS provides for the creation of virtual ones, the number of which is unlimited.

A serial or COM port is an RS-232 interface that is used to connect various equipment to a computer. Due to the limitation in the amount of information (1 bit) transmitted at a time, this port received a second name: serial. An interesting fact is that in various interfaces, such as Ethernet or USB, information is also transmitted - sequentially, however, such a name has not been assigned to them.

What to do if the computer does not have a COM port?

Initially, COM ports were used to connect terminals, modems, and mice. In modern times, the main purpose is to connect all kinds of power sources, microcontrollers, computer systems, cash registers and other devices. Also, the COM port was very actively used to synchronize computers: for example, a laptop with a personal computer. Now this approach has been replaced by the use of a USB port.

What is a virtual COM port?

A virtual COM port is imagined by our operating system, while it is not physically present. For "imagination" there are special programs, one of which we will consider later.

What is it used for?

Once you understand what a real COM port is and what it is used for, you can easily imagine the need for a virtual COM port. Imagine: you need to connect a computing device to a computer via a COM port. But you don't have it! Or connect several devices, and there is only one port. How to be in such a situation? It is the creation of a virtual port that saves.

Thus, the virtual port allows you to simulate its presence in the computer in the absence of it. There are quite a few examples of application. However, the most commonly used virtual COM port is:

• If necessary, connect multiple devices at the same time.
• If necessary, debug (test, find errors) a program for a computing device in the absence of a port.

How to create virtual ports?

For their creation, specialized programs are provided. It is worth choosing those that offer us to install the drivers we need for virtual ports, since searching for them is not a very pleasant experience.

Download and install the Advanced Virtual COM Port program. Installation takes a matter of minutes, while at one of the stages we will be offered a driver:

We agree and click "Install". You should wait a few minutes - don't be alarmed if it takes 5-10 minutes. This is fine.
After installation, we go into the program and see the main window:

It contains three main tabs: General (advanced), client and local ports.

tab common (or extended) ports allows you to share COM ports over a local area network (LAN) or the Internet. Thus, data from virtual ports can be easily and quickly transferred to other users.
tab client ports allow you to create ports on your computer that connect to extended ports via a virtual null modem cable. It is worth saying that the program automatically provides a virtual cable.
tab local ports allows you to view, create and delete all pairs of virtual COM ports.

Go to the Local Ports tab and click the Add button. A window will open in front of us, offering to create a pair of COM ports that are supposed to be connected by a virtual null modem cable:

We press OK. Go to Control Panel -> System -> Device Manager.
We see that our COM ports have been successfully created:

Interaction of extended and client COM ports

Most likely, the question of the interaction of these two tabs remains unclear. In fact, everything is simple: extended ports allow you to share your com-ports, that is, all the information that is available from devices connected to these ports. They connect to client: those that receive all the necessary information.

To create an extended port, just click the Add button in the first tab and select the port that we are sharing:

To create a client port, go to the second tab, click the Add button and first select the port that we want to make a client port, and then the address of the computer to which we want to connect:

Results

There are still a lot of interesting things left overboard on the topic of COM ports. Although this technology is fading into the background with the development of other interfaces for connecting devices, nevertheless, for the time being it is still actively used and it is very useful to know the intricacies of its operation.

First, a few words about the microcircuit PL2303. There are 2 common versions of this chip: new (var D 2012) and old (var A 2004). According to the Datasheet, they have a different pinout, so you need to look at what version of the microcircuit you have. This article applies only to the old version of the chip.

Option adapter with pairing levels.

The PL2303 chip can completely replace the COM port, but I only use the Tx and Rx pins. The rest I discard as useless. The diagram of this adapter is shown in Figure 1.

To interface levels between USB and COM port, I use the MAX232 chip. This microcircuit is needed due to the fact that in a classic COM port, the logical levels are + -12 volts, and USB works with 0-5 volt levels.

Figure 1 - Scheme of the USB-COM-port adapter on the PL2303 chip with level pairing

The printed circuit board of this adapter is contained in the files to the article.

Adapter option without level pairing

If there is no need for level pairing, you can discard the part of the circuit with the MAX232 chip. After the change, the circuit shown in Figure 2 is obtained. This variation of the circuit is well suited for connecting microcontrollers via UART (the mass of the microcontroller and the adapter must be common).

Figure 2 - Scheme of the USB-COM-port adapter on the PL2303 chip without level pairing

The printed circuit board is also contained in the files for the article.

Figure 3 shows the finished device. Although the board was originally made for the first option, the MAX232 chip was later dismantled as unnecessary. Now the adapter is successfully used to connect AVR microcontrollers to a computer via UART.

Figure 3 - Photo of the finished device

Driver for PL2303 chip

For the driver, go to the manufacturer's website and download the latest version of the driver. Driver Link

Possible problems

Driver problem says " This device cannot be started. (Code 10)". There are two solutions:

1) install the old version of the driver. You can download the old driver there. I have windows 10 and this method did not help me much.

2) download the crutch to the driver (it is in the files to the article.). I don't remember where I got it from, but it helped me. After download:

• ser2pl.inf - right click and install
• Copy everything to C:/Windows/System32/Drivers

To check the performance of the adapter, you need to close the Rx Tx contacts and send some data to the COM port, the data should return. To monitor the COM port, I use the program Advanced Serial Port Monitor.

List of radio elements

Recently (more precisely, for many years) computers, both laptops and desktops, are not equipped with RS-232 serial ports. The need for this interface simply disappeared - there are practically no mass external devices on the market that connect via a standard COM port. But, nevertheless, there are a lot of applications and devices that use only RS-232/422/485 serial ports. These are various receivers in which flashing is performed via a serial port, diagnostic equipment for cars and much more. If there is no such port in the computer, then what to do?

You can buy specialized USB to RS-232 serial adapters at almost any computer store. The price range of such adapters is simply huge: from $1 for a "string" of dubious origin on eBay, up to $30-50-100 for devices, some of which are no different in appearance from a one-dollar "string". So what to choose? The Internet is full of both positive and negative reviews about very inexpensive adapters. For some they work without problems, for someone the same model refuses to work to death. Why? There are two possible problems here: it can be either a software problem or purely hardware problems.

Firstly, I will say a banality that you should not expect miracles from inexpensive devices. Quality software is not something a small company can afford. Yes, and components for production are also very different in price.

Why doesn't my USB-COM adapter see my device?

There are several possible reasons.

1. What does such an adapter generally consist of? Ideally - from a USB bridge to a serial port and a level converter to RS-232. The fact is that the output bridge has TTL levels, i.e. from 0 to (for these bridges) a maximum of 3.3 V. Often the voltage does not even reach 3 V. According to the RS-232 standard, the signal must be from ± 5 V to ±15 V, moreover, the receiver must receive a signal with a spread of ±3 V. Here we see the reason for the first savings - often the manufacturer simply does not use a level converter, since, theoretically, + 5V ± 3V gives as much as + 2V, and at the output, as a rule, from +2.5 to 3.3V, but it is impossible to get a logical 1 with a voltage of even -2 to -15 V. Those. even in principle, such an adapter cannot work with RS-232, only with controllers that also have TTL levels at the input. However, there are also such devices, however, infrequently. There is another problem: some RS-232 chips include a power-saving mode (sleep mode). If the inputs are less than ±3V, it will not even come out of "hibernation", i.e. in the case without a level converter, with an output voltage of 2.5 V, never at all. In the "correct" adapters, the typical voltage at the outputs is ± 6.5V, which is well within the standard.

Figure 1. "Correctly" made adapter-cable USB-COM Mini:

The wires are not soldered directly to the board, but connected by a connector. This prevents mechanical breakage of the wires.
There is an indication - 2 LED.
The board itself is varnished, all holes are covered with gold against oxidation.
Two microcircuits: both a bridge (in this case, FTDI FT232RL), and a level converter ZT231LEEA.
High-quality installation, high-quality element base.

If you often have to use the adapter, carry it constantly in your bag, connect it in rooms with a dusty or aggressive environment, then all these "little things", which most manufacturers usually save on, will not seem trifles to you. In addition, all 9 RS-232 signals are wired, which allows using this adapter with any RS-232 devices.

2. Another quality criterion is the adapter's support for all 9 standard RS-232 signals. In many models of inexpensive adapters, only 3 out of 9 signals are supported. For many devices, this is quite enough, for example, to control a frequency converter. Other devices, such as barcode readers, require all 9 signals. Again, an adapter that has a full set of modem signals can easily work with any RS-232 devices, and those that use only 3, alas .... And manufacturers do not always advertise this property of their products. So when looking for an adapter, check what signals are needed to connect your device, and check that the adapter you have chosen supports them. By the way, not all USB-UART bridges support all modem signals.

Many people who have their hands screwed in properly want to make such adapters themselves. You can find schematics, PCB drawings and detailed recommendations on the Internet. Is the game worth the candle? Of course, if for you personally this is a matter of principle, then this is understandable. But looking at the prices of microcircuits, for example, I would lose all interest in such work. Only the TTL to RS-232 MAX213EWI level converter chip costs 200 rubles at retail. At the same time, this chip operates at a maximum speed of only 115 Kbps, and not 921 Kbps, as in the "correct" models. Have you thought why they are not put in cheap adapters? The most inexpensive USB-UART bridge PL2303 costs 210 rubles, FT232RQ - 360, FT232RL - 460, TUSB3410 - 530 rubles. Here I would like to note that the FT232RQ, FT232RL microcircuits are the same, only with a small, but for someone very significant difference - the MTBF of the first microcircuit is 2.5 times less than that of the second. Although this time is not at all small. This is without attachments, boards, connectors and housing. So, before taking on such a job, it makes sense to think, maybe ready-made is also a good option? However, everyone knows that some manufacturers (the Chinese, although it’s not politically correct to point a finger at them) can make a low-quality product out of FTDI and Texas Instruments, to put it mildly, so look more closely at the manufacturer and his reputation.
And yet, if you decide to make such an adapter with your own hands, in the datasheets of chip manufacturers you can find detailed diagrams of such devices for every taste. Once again I will repeat the links to the most popular microcircuits: