Do-it-yourself USB-COM adapter: diagram, device and recommendations. Zero modem cable (RS232) pinout connect usb rs232

10.02.2022

Audio

Problems with the "firmware" of the receivers. No COM port. Laptop use

Most of the "old" computers and laptops, purchased more than 5 years ago, always had several COM ports (RS-232). At least there was always at least one "RS-232" connector.

Rice. 1. Connector on the computer case

Various external equipment was connected to it: mice, printers, modems, specialized equipment. Therefore, there were no problems connecting the receiver to the computer for “firmware”. It was enough just to connect, run the program to update the receiver software and calmly do everything you need.

In modern computers, the RS-232 connector is often missing. This is where problems arise, often very unpleasant ones. In most receivers there is no other way to "firmware" other than using "RS-232". And not all receivers have a “USB” input for connecting an external flash drive.

And sometimes there is another problem: the laptop has a "COM" port, but it works with receivers of one model, but not with others. This is due to the violation by the laptop manufacturer of the RS-232 data transfer standard. They do this in order to conserve battery power. If the manufacturer of the receiver was technically scrupulous and accurate, then a special chip for the "COM" port will be installed in the receiver. Thanks to this chip, the receiver will work with both a laptop and a computer. But installing a microcircuit increases the total cost of the product, and lately manufacturers have been saving even on these little things! Therefore, there is a problem of incompatibility between laptops and most receivers.

When using a computer, the problem of the lack of the necessary RS-232 ports is solved simply: you need to purchase an additional module with COM ports. This board installed in the computer is called "PIC-COM" or simply "COM ports board".

Rice. 2. PCI board for computer with two "COM" ports

If you are not strong in computers and have never dealt with the installation of additional equipment in a computer, then contact a specialist! Otherwise, you can "kill" expensive equipment.

After the board is installed in the computer, the operating system "Windows" - "OS" assigns a number to the newly installed ports, for example, "1", "2" ... "25".

When using a laptop, you cannot install a regular board from a computer: the standard and size are not the same. There are two ways to solve this problem: expensive, but high-quality, and cheap, but not fully compatible. In the first case, you need to purchase a special board with ports for the laptop. The price of these boards is high, and I was not able to purchase this board, even on order.

Rice. 3. Laptop board with "COM" port

And there is a catch: in the "old" and "new" laptops, there are two different standards for additional equipment! Before purchasing, check the instructions for your laptop!

If you could not purchase a board for a computer or laptop, then there is only one way out: “USB”. Almost all modern computer models have a “USB” output, at least two, or even all eight! Various "USB - COM" converters are commercially available.

Rice. 4. Converter "USB - COM"

Rice. 5. Scheme of the converter "USB - COM"

How to solder a USB-COM adapter yourself. Option 1

How to make a USB-COM adapter yourself, which can be used to connect converters and other devices to computers that do not have an "iron" COM port.
Attention!
The adapter described below ensures that only the RX and TX signals are matched.
All other modem signals are disabled.
For most devices without hardware flow control, this is more than enough.
With Pilot VAF / MAF converters, the adapter works 100%

Go!

You will need the following parts for assembly:

1. PL2303HX (USB-USART bridge from Prolific) - 1 pc.
2. MAX232CSE (UART-RS232) - 1pc.
3. Quartz 12.00 MHz-1pc.
4. Capacitors 10 nF (smd1206) - 2 pcs.
5. Capacitors 1uF (smd1206) - 6pcs.
6. Resistors 27 Ohm (smd1206) - 2 pcs.
7. Resistors 1.5KΩ (smd1206) - 1 pc.
8. Mini-USB connector -1pc.
9. Connector DB-9 male - 1 pc.
10. Foil textolite for the board 48 * 22mm - 1 pc

Adapter diagram

Printed circuit board

Schematic and printable files in the format Eagle PCB Editor can be downloaded from this link

Assembly and setup
Here, in fact, everything is elementary - we make a board, drill 4 holes and solder all the details.
As a result, you should get such an adapter:

The board, so that it does not oxidize, can be blown out with polyurethane varnish or any quick-drying automotive varnish that is at hand.
Next, we connect this device to the USB port of the computer.
Windows will detect a new device and ask for a driver

We go to the profile site and download the latest version of firewood

At the time of this writing, the most recent driver was this one.

After feeding the Windows driver, a new Prolific COM port should appear in the system:

Now you need to check the performance of the adapter

To do this, on the adapter in the COM port connector, with a screwdriver or wire, we close pins 2 and 3 together (digits with pin numbers are usually stamped on the connector itself - take a closer look) Alternatively, you can solder a temporary jumper:

Next, run the program "Hyperterminal" (Start->Programs->Accessories->Communication->Hyperterminal)
There is no hyperterminal on Vista and Seven! Therefore, you will have to go to Google / Yandex to download the hyperterminal or any of its analogues.

We select our new COM port in the connection settings:

Now we start the connection, select the English layout and try to print something.

The symbols of the pressed keys should appear on the screen:

If the letters do not appear, then check the installation

That's actually all!
Now it remains to remove the jumper from pins 2-3 and you can use the adapter for its intended purpose.

Those. the input of such a “converter” is connected to the free “USB” connector of the laptop, the driver (control program) is installed from the disk from the kit, and a virtual COM port with the assigned serial number appears in the system settings.

How to solder a USB-COM adapter yourself. Option - 2

Picture 1.General form

The proposed block in assembled form allows you to implement the principle: bought - connected. The device will allow users of personal computers to connect devices operating from the COM port (RS232C) to the USB port.

Estimated retail price: 540 rubles

The adapter will be useful in practical applications: for connecting various devices to a personal computer, as well as modems and programmers.

Specifications

Supply voltage from the USB port: 5 V.

Consumption current: 20 mA.

RS232C connection speed: 110-230000 bps

Interface: USB1.1, USB2.0.

Supported operating systems: Win98, Win2000, WinXP, Vista, Linux, etc.

Overall dimensions of the device: 60x30 mm.

Contents of delivery

Adapter block assembly: 1.

Instruction: 1.

Design

Structurally, the adapter is made on a double-sided printed circuit board made of foil fiberglass, protected by a transparent heat shrink tube.

The adapter provides all modem signals: DSR, DTR, RTS, CTS, RI, DCD, as well as the main RXD and TXD signals.

Figure 2. Electrical circuit diagram

Figure 3. View of the printed circuit board from the parts

Description of the block

The circuit diagram is shown on pic 2.

The central part of the device is a CP2102 microcontroller manufactured by SILICON LABORATORIES. The MAX3243 converter manufactured by Texas Instruments is used as a level driver chip. The adapter provides all modem signals: DSR, DTR, RTS, CTS, RI, DCD, as well as the main RXD and TXD signals.

Installing the device in the OS

To install drivers for your computer, you must first download the appropriate driver for your operating system.

Next, install the driver on your personal computer. Plug in the adapter. The operating system will detect it and "ask" for the driver, you should tell it the location of this driver (the place where it was unpacked).

After successful installation, the LED on the adapter should light up, signaling the readiness of the device for operation!

NEW Updated driver from 01/25/2011

1. Driver for Win Vista You can download

2. Driver for Windows 2000/XP/Server 2003/Vista (v5.0) You can download

3. Driver for Linux You can download

4. Driver for Win98SE You can download

5. Driver for OC Mac You can download

6. an144sw.zip- using this program, you can change the ID codes of the USB-COM adapter. This is necessary in order to be able to use several 8050s on one PC. Use by advanced users only! You can download

BM8050 FUNCTIONAL TEST WITHOUT EXTERNAL HARDWARE

To check the transmission and reception of all necessary modem signals according to the connection of the COM device.

Install jumpers on pins 2-3, 4-6, 7-8 of the BM8050 COM connector.

Connect the device to the USB port of the PC.

See which port the OS has allocated for the device by going to Start --- Settings --- Control Panel --- System --- Hardware --- Device Manager --- Ports (COM and LPT) --- Silicon Labs CP210x USB to UART Bridge (COM1).

Launch the standard HiperTerminal Windows application from Start --- Programs --- Accessories --- Communications --- HiperTerminal.

Stop a running connection, if it is active, to do this, click Call --- Stop at the top.

See which port is used by the program to communicate with the device, for which go to the top left File --- Properties and opposite "Connect via" select the same port as in the Device Manager (in our case COM1).

In the same window, make sure that "Hardware" flow control is selected in the program, for which click the button in the "Settings" center and select "Hardware" in the lower "Flow Control" window.

Exit the program settings by clicking OK, OK again.

Type the text "Text" in the HiperTerminal program, while the text "Text" is printed on the screen, which confirms that the device is working.

Remove the jumpers from pins 2-3, 4-6, 7-8 of the BM8050 COM connector.

Type the text "Text" in the HiperTerminal program, while there is no print on the screen, which confirms that the device is working.

Driver setup and port selection for USB-COM adapter

Here the first problems await us: firstly, the OS could assign too large a number to the virtual port, for example, "25". And the program for "firmware" of the receiver allows you to work with port numbers from one to four. Secondly, not all USB-COM converters can work with the firmware program and the receiver itself. The reason is that equipment manufacturers have manufactured their products and programs in different ways. It is necessary to check all converters individually for your program and your receiver. It often happens that the converter works with one equipment, but not with another.

If the first problem is solved by changing the port number in the OS settings, then the hardware, program, and converter compatibility problem cannot be solved.

To change the assigned OS number, you must change it manually. To do this, you need to enter the "Device Manager": "Start" - "Settings" - "Control Panel" - "System".

Rice. 15.6. "Control Panel"

In the window that appears, select the "Hardware" tab and click on the "Device Manager" button. The Device Manager window will open. In the window that appears, in the tree-like list, select the line “Ports (COM and LPT). In the drop-down list, you will see all the ports available on your computer. Select your virtual port: "USB to COM converter". I have a "Prolific" model converter.

Rice. 15.7. List of available ports

Click on this line with the RIGHT mouse button, in the window that opens, select the “Properties” option.

Rice. 15.8. Setting the selected port

In the window that appears, select the "Port Settings" tab. In the "Speed" line, select "115200", then click on the "Advanced" button.

Rice. 15.9. Configuring Port Settings

At the bottom of the window that opens, find the "COM Port Number" tab.

Rice. 16. Change the COM port number

Click on the tab and select the desired COM port number.

Note that some port numbers may be occupied by existing equipment, such as the built-in modem. You cannot use one port at the same time!

After completing the settings, click "OK" to save the changes made and completely exit the settings mode by closing all previously opened windows. After that, restart your computer to make the necessary changes. If you changed the “COM” number of the “USB - COM” port of the converter, then simply remove it from the computer connector and reconnect it.

Ready-made solutions for USB-COM adapters from manufacturers.

Adapter cable COM 9/25M -> USB AM 1m

Price - 300 rub.
Description Cable for connecting devices with a serial interface (RS-232) to the USB port.
Cable connectors or adapter COM25M, COM9M, USB A
Compatibility
USB 1.1/2.0 Compatibility
Support for Windows 2000, Windows XP
Other
Cable length 1 meter
Logistics
Package dimensions (measured in NYKS) 21.5 x 14.5 x 4.1 cm
Gross weight (measured in NYX) 0.136 kg

TRENDnet adapter cable COM9M-->USB AM 0.6m

Price - 500 rub.
Main
Manufacturer TRENDnet
Model TU-S9
Type of equipment Adapter cable
Diameter 28/24 AWG
Performance options
Data transfer rate 500 Kbps
Powered by USB port
Power consumption 500 mA - maximum
Compatibility
System requirements RAM 64 MB
Support for Windows ME, Windows 2000, Windows XP
Other
RoHS Compliance
Cable length 0.6 meters
Weight 75 grams
Operating temperature 0 ~ 40°C

Package dimensions (measured in NYX) 23 x 16.8 x 4.6 cm
Gross weight (measured in NYX) 0.135 kg
External sources of information
Link to the manufacturer's website www.trendnet.com

Adapter - USB-COM adapter (RS-232)

Price - 1500 rub.
The adapter is designed to use devices and adapters designed to be switched on via the Com (RS232) port, for example, this is very important when using modern computers that have only USB, in this case, using this adapter, you can use modern computers and laptops in conjunction with our devices and adapters such as Scanner BMW, Scanner Mercedes, Scanmatik, etc.

Car service equipment, car diagnostics, diagnostic equipment, car diagnostics, car scanner, car scanner, diagnostic post, chip tuning, car diagnostic equipment Carbrain, UNISCAN, ADP-504, KKL-USB, KKL-COM, BMW scanner, Opel scanner, BMW 1.3 .6, Automan, Opel scanner, BMW scanner, engine tester, gas analyzer, engine diagnostics, dashboard diagnostics Transponder programmer, OBD-2, OBD2, odometer correction, U-581, engine start, crash data, crash date, crash date, speedometer, tachometer.

Although you may need to use a null modem cable (2-3, 3-2, 5-5) and an adapter like -

Add to the adapter USB extension cable here's a straight-through null modem cable.

Retail value 100r.
Type A-A
Length: 1.5 m

But for the rest of the resources you need " flipped over" null modem cable.

Retail price 155.00 RUB
Connector type: DB9 F - DB9 F
Length: 1.8 m

or this adapter:

STLab U-350 (RTL) Adapter COM 9M -> USB AM

Price - 350 rub.
Main
Manufacturer St-Lab
Model USB DONGLE SERIAL 1 PORT
Description The adapter allows you to connect a device with an RS-232 interface (for example, a modem) to a USB port on your computer.
Type of equipment Adapter cable
Cable connectors or adapter COM9M, USB A
Integrated USB connector Yes
Performance options
Transfer rate 115200 bps
USB 1.1 interface
Powered by USB port
Support for Windows 2000, Windows ME, Windows XP, Windows Vista, Windows 2003 Server
Package dimensions (measured in NYX) 17 x 13 x 3.2 cm
Gross weight (measured in NYX) 0.077 kg
External sources of information Link to the manufacturer's website

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 routed, 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:

Problems with the "firmware" of the receivers. No COM port. Laptop use

Most of the "old" computers and laptops, purchased more than 5 years ago, always had several COM ports (RS-232). At least there was always at least one "RS-232" connector.

Rice. 1. Connector on the computer case

Rice. 2. PCI board for computer with two "COM" ports

If you are not strong in computers and have never dealt with the installation of additional equipment in a computer, then contact a specialist! Otherwise, you can "kill" expensive equipment.

After the board is installed in the computer, the operating system "Windows" - "OS" assigns a number to the newly installed ports, for example, "1", "2" ... "25".

Rice. 3. Laptop board with "COM" port

And there is a catch: in the "old" and "new" laptops, there are two different standards for additional equipment! Before purchasing, check the instructions for your laptop!

Rice. 4. Converter "USB - COM"

Rice. 5. Scheme of the converter "USB - COM"

How to solder a USB-COM adapter yourself. Option 1

Go!

You will need the following parts for assembly:

1. PL2303HX (USB-USART bridge from Prolific) - 1 pc.
2. MAX232CSE (UART-RS232) - 1pc.
3. Quartz 12.00 MHz-1pc.
4. Capacitors 10 nF (smd1206) - 2 pcs.
5. Capacitors 1uF (smd1206) - 6pcs.
6. Resistors 27 Ohm (smd1206) - 2 pcs.
7. Resistors 1.5KΩ (smd1206) - 1 pc.
8. Mini-USB connector -1pc.
9. Connector DB-9 male - 1 pc.
10. Foil textolite for the board 48 * 22mm - 1 pc

Adapter diagram

Printed circuit board

Schematic and printable files in the format Eagle PCB Editor can be downloaded from this link

Assembly and setup
Here, in fact, everything is elementary - we make a board, drill 4 holes and solder all the details.
As a result, you should get such an adapter:

We go to the profile site and download the latest version of firewood

At the time of this writing, the most recent driver was this one.

After feeding the Windows driver, a new Prolific COM port should appear in the system:

Now you need to check the performance of the adapter

We select our new COM port in the connection settings:

Now we start the connection, select the English layout and try to print something.

The symbols of the pressed keys should appear on the screen:

If the letters do not appear, then check the installation

That's actually all!
Now it remains to remove the jumper from pins 2-3 and you can use the adapter for its intended purpose.

How to solder a USB-COM adapter yourself. Option - 2

Picture 1.General form

Estimated retail price: 540 rubles

The adapter will be useful in practical applications: for connecting various devices to a personal computer, as well as modems and programmers.

Specifications

Supply voltage from the USB port: 5 V.

Consumption current: 20 mA.

RS232C connection speed: 110-230000 bps

Interface: USB1.1, USB2.0.

Supported operating systems: Win98, Win2000, WinXP, Vista, Linux, etc.

Overall dimensions of the device: 60x30 mm.

Contents of delivery

Adapter block assembly: 1.

Instruction: 1.

Design

Structurally, the adapter is made on a double-sided printed circuit board made of foil fiberglass, protected by a transparent heat shrink tube.

The adapter provides all modem signals: DSR, DTR, RTS, CTS, RI, DCD, as well as the main RXD and TXD signals.

Figure 2. Electrical circuit diagram

Figure 3. View of the printed circuit board from the parts

Description of the block

The circuit diagram is shown on pic 2.

Installing the device in the OS

To install drivers for your computer, you must first download the appropriate driver for your operating system.

After successful installation, the LED on the adapter should light up, signaling the readiness of the device for operation!

NEW Updated driver from 01/25/2011

1. Driver for Win Vista You can download

2. Driver for Windows 2000/XP/Server 2003/Vista (v5.0) You can download

3. Driver for Linux You can download

4. Driver for Win98SE You can download

5. Driver for OC Mac You can download

BM8050 FUNCTIONAL TEST WITHOUT EXTERNAL HARDWARE

To check the transmission and reception of all necessary modem signals according to the connection of the COM device.

Install jumpers on pins 2-3, 4-6, 7-8 of the BM8050 COM connector.

Connect the device to the USB port of the PC.

Launch the standard HiperTerminal Windows application from Start --- Programs --- Accessories --- Communications --- HiperTerminal.

Stop a running connection, if it is active, to do this, click Call --- Stop at the top.

In the same window, make sure that "Hardware" flow control is selected in the program, for which click the button in the "Settings" center and select "Hardware" in the lower "Flow Control" window.

Exit the program settings by clicking OK, OK again.

Type the text "Text" in the HiperTerminal program, while the text "Text" is printed on the screen, which confirms that the device is working.

Remove the jumpers from pins 2-3, 4-6, 7-8 of the BM8050 COM connector.

Type the text "Text" in the HiperTerminal program, while there is no print on the screen, which confirms that the device is working.

Driver setup and port selection for USB-COM adapter

If the first problem is solved by changing the port number in the OS settings, then the hardware, program, and converter compatibility problem cannot be solved.

To change the assigned OS number, you must change it manually. To do this, you need to enter the "Device Manager": "Start" - "Settings" - "Control Panel" - "System".

Rice. 15.6. "Control Panel"

Rice. 15.7. List of available ports

Click on this line with the RIGHT mouse button, in the window that opens, select the “Properties” option.

Rice. 15.8. Setting the selected port

In the window that appears, select the "Port Settings" tab. In the "Speed" line, select "115200", then click on the "Advanced" button.

Rice. 15.9. Configuring Port Settings

At the bottom of the window that opens, find the "COM Port Number" tab.

Rice. 16. Change the COM port number

Click on the tab and select the desired COM port number.

Note that some port numbers may be occupied by existing equipment, such as the built-in modem. You cannot use one port at the same time!

Ready-made solutions for USB-COM adapters from manufacturers.

Adapter cable COM 9/25M -> USB AM 1m

TRENDnet adapter cable COM9M-->USB AM 0.6m

Package dimensions (measured in NYX) 23 x 16.8 x 4.6 cm
Gross weight (measured in NYX) 0.135 kg
External sources of information
Link to the manufacturer's website www.trendnet.com

Although you may need to use a null modem cable (2-3, 3-2, 5-5) and an adapter like -

Add to the adapter USB extension cable here's a straight-through null modem cable.

Retail value 100r.
Type A-A
Length: 1.5 m

But for the rest of the resources you need " flipped over" null modem cable.

Retail price 155.00 RUB
Connector type: DB9 F - DB9 F
Length: 1.8 m

or this adapter:

STLab U-350 (RTL) Adapter COM 9M -> USB AM

In modern computers and laptops, manufacturers have stopped using the COM port, which was widely used earlier. If you have an old computer that you bought about 7 years ago, you can find several of these ports on it. The COM port was designed to connect various external equipment, such as a mouse, printer, modem, and other special tools. Now there are problems with connecting various outdated equipment to new laptops or computers. For example, it is quite difficult to connect a receiver now, since you need to use a COM port for this.

What to do in this case? There is, of course, a way out. You can make a USB to COM converter yourself. How to do it? In this article you will find answers to your questions.

Do-it-yourself USB-COM adapter

Now we will look at how to make a USB-COM adapter that will work with RX and TX signals. It will not work with other types of modem signals, but this is quite enough to connect standard equipment.
To proceed with the assembly, you will need to purchase the following parts:

Two 10nF capacitors and one 1uF capacitor.
Two 27 ohm resistors and one 1.5 kΩ resistor.
Mini-USB connector and DB-9 one each.
Quartz 12.00 MHz.
PL2303HX.
Foil textolite for board 48*22 mm.

After purchasing these parts, you can proceed directly to the assembly. First, we will need to consider the USB-COM adapter circuit (you can see the image below).

Assembling and setting up the adapter

There is nothing difficult in the installation. First you need to take or make your own fee. After that, we drill four holes. Next, we need to solder all the details, the location of which will correspond to the diagram. This completes the assembly.

To prevent the board from oxidizing, it must be blown out with polyurethane varnish. If this is not available, you can use any other quick-drying car varnish.

It's time to move on to the setup. We connect our board to the computer. If everything is assembled correctly, it will determine the device on which you need to install the drivers.

We install the Prolific drivers for such a port on the computer. By going to the "Task Manager", you can see that it has been determined and is now fully functional.

Examination

To check the performance of our adapter, you need to close the contacts near the COM port with some thin object (see the image below where this needs to be done).

Go to the "Connection settings" section, where you need to select the COM port. In a new window, you should configure the following parameters of our port:

signal transmission rate - 115200;
data bits - 8;
parity - no;
stop bits - 1;
flow control - no.

Next, confirm the changes by clicking the OK button. After that, you should start the connection. We turn to the English layout and print any words in the program. All the characters you clicked will be displayed on a white background.

In the event that this does not work, that is, the words are not displayed, you need to change the installation. We adjust it until the characters are displayed.

That's all. You can release the pins that you clamped and start using the USB-COM adapter.

USB RS232 DB9 COM adapter cable

If you are unable to make your own adapter, you can purchase USB RS232 DB9 COM. Its price varies within 1000 rubles, and it has pretty good technical characteristics. Probably the most important thing is a good connection speed. It is also supported by almost all operating systems. Unfortunately, it only works with USB 2.0.

Connecting to a computer

To connect the USB RS232 DB9 COM adapter to your computer, you need to search the Internet for drivers suitable for your operating system. Download and unpack them. We connect the adapter to the computer, after which we indicate where the drivers are located. If everything was done correctly, the LED on the device will light up, indicating that it is ready for operation.

Possible problems

Unfortunately, even when you use a purchased USB-COM adapter cable, problems may occur. They must be fought, and it is not difficult to do this.

Alternative solution to the problem

If you need to install additional equipment that needs a COM port, you can also use a module with this connector. It is simply installed directly in the computer and connected to the motherboard. After installing the COM-port card or PIC-COM (second name), it is also assigned a number. As in the previous cases, this number can be changed if problems arise. If you are not sure that you can properly install this board in your computer, it is better to take the help of professionals so as not to harm other equipment.

Unfortunately, this solution can only be used for computers. In laptops, it is quite difficult to install an additional board, and this requires additional costs. Firstly, the case itself will not allow you to install an additional module, and secondly, it may not be supported by your model. Therefore, in the case of a laptop, you should use a USB-COM adapter.

Conclusion

If you need to connect outdated equipment that requires a COM port, you can make an adapter yourself. It's pretty simple. If you do not want to do this, you can purchase a USB-COM adapter. Its price is about 1000 rubles. Remember that you still have to install drivers and check the functionality of this hardware. On Windows 7, the USB-COM adapter is quite easy to install, since you can find all the drivers for this operating system on the Internet.

A COM USB adapter is a device that allows a personal computer to be connected to various peripheral equipment. Unfortunately, modern models of system blocks sometimes do not have very important outputs. Thus, the user is limited in their capabilities.

If we consider such a device as a receiver, then it cannot be connected to a cable. In this case, the user can only help. By the type of connectors, these devices differ. In addition, it should be noted that it is quite possible to make them at home. However, first of all, it is important to familiarize yourself with their device.

Diagram of a simple adapter

The USB-COM adapter circuit includes a port, a modulator, a converter, and a resistor. In some cases, an amplifier may be additionally located on the board. In this case, wired models are most often selected. Resistors in this case are used only open type. This is necessary in order to increase the maximum frequency of the device. Thus, the response time of the signal will be in the region of 20 ms. Among other things, you should consider the bandwidth of the device. To increase this parameter, many experts advise modulators to use only two-sided ones.

Models type A standard

Making a type A USB-COM adapter with your own hands at home is quite simple. In this case, it is more expedient to select a microcircuit of the PP21 type. Only the converter will help stabilize the process in the device. For normal operation of the model, a high-quality modulator will also be required. For the specified microcircuit, it is necessary to select only a low-frequency type. All this will allow the signal response parameter to be kept at around 30 ms.

For better current conductivity, experts also advise using low power transistors. In this case, they must withstand the maximum voltage at the level of 3V. In general, these adapters are great for various kinds of receivers. In addition, radio receivers with SR101 connectors can be connected to them.

Type A mini models

Adapters of this type are capable of supporting many formats. It is impossible to add them without converters. Additionally, you will need to pick up a chip of the PP22 series. There should be three transistors in total. In this case, two of them must be placed near the converter. In this case, it is important to select a modulator of a pulse type. The response speed of the signal is on average about 30 ms. For stable operation, this is quite enough.

The cable in this case must be attached to the back of the chip. It is important not to touch the modulator during the soldering process. Transistors also need to be kept clean. The pairing of the circuits is provided by the frequency amplification stage. On average, this parameter fluctuates around 12 Hz. To increase the conductivity of the current, some experts advise the use of amplifiers. The device port is connected last. The driver for the USB-COM adapter is selected separately.

Type A micro models

Making a type A micro USB-COM adapter with your own hands is quite difficult. This is largely due to the presence of a non-standard port. The throughput for it should be provided quite high. In this case, the minimum signal response parameter must be 20 ms. Separately, you should also pay attention to the search for a converter.

To increase the clock frequency in the device, many of them select a symmetrical type. In this case, transistors are selected in an open modification store. On average, they withstand voltage at 3A. As an option, you can consider combined subspecies. All this will ultimately increase the signal response speed.

How to make an adapter type B standard?

The presented USB-COM adapter cable is assembled for devices that have a connector of the RSR21 type. First of all, you need to select a modulator in the store. In this situation, you can stop at the step analog. However, its bandwidth is quite low. Also, in the future, certain problems with overlapping contours may arise. To solve the presented problem, you can use oscillatory modulators.

They are quite expensive on the market, but device testing shows that they are very good. First of all, they differ in the presence of copper contacts. Thus, their current conductivity is high. Among other things, it works quite well with a PP20 type chip. The port in this case must be installed last. In this case, the cable for it is selected separately.

Adapter type B mini

This COM USB adapter is assembled using a PP220 chip. In this case, the converter must be selected with a chromatic resistor. Additionally, it is important to use only a high-frequency modulator. To increase the signal response speed, many experts advise using open-type transistors.

However, the devices will decrease significantly. As a result, there may be a problem installing the device driver. Additionally, a trigger is mounted on the USB-COM adapter. This element in the system is responsible for conjugation of contours. This process takes place in a grid triode. This increases the frequency gain significantly. The port for the adapter is selected without a selector.

Type B micro model

Adapters of the presented type are assembled quite simply. First of all, it should be noted that today they are quite in demand. They are suitable for all devices that have an RSR 23 type connector. Converters are selected for a microcircuit of only a pulse type. In this case, it is best to use standard transistors. However, many experts still give their preference to analogues of the open type.

The bandwidth parameter in this case will depend on the type of amplifier. If you use a low-frequency modification, then problems with the device are inevitable. In turn, longitudinal modifications significantly increase the current permeability parameter. The cable in this case is soldered to the convection output of the microcircuit.

How to choose a model in the store?

For devices with a RSR21 connector, the adapter should be selected high-frequency. It must withstand a minimum load at the level of 3 A. The copper of the conductors must be oxygen-free. In this case, you can count on a good device bandwidth. The adapter must support Dolby and True digital formats.

In turn, the video system must work with 720p. Amplifiers in devices, as a rule, are installed non-contact. However, some models have cheaper analog modifications. The outer shell of the model must be made of PVC. The signal response speed parameter is on average around 30 ms. A quality adapter will cost about 2500 rubles.

Specifications USB mini 4P

This one differs from other devices in that it has a two-way modulator. Due to this, he is quite good. For audio devices, this model fits perfectly. In this case, the traverse is installed intermediate. To stabilize the signal in the device, a high-frequency amplifier is used. The model signal response speed parameter is at the level of 25 ms. On average, the frequency indicator of the device is located at around 23 Hz. To adjust the current, the adapter has a small reflector.

Model USB 1394B

Adapters of this type are capable of boasting a fairly high signal response speed. In this case, there is a low-frequency converter. In turn, the modulator is set with a limiting frequency of 23 Hz. All this allows you to quickly stabilize the input voltage. Support for major formats is provided by installing the device driver. The amplifier in this case is of a pulsed type. In turn, high throughput became possible by increasing the generation parameter.

The disadvantages of this adapter include a low overlap range. In this regard, conflicts often arise with the system when connecting peripheral devices. Additionally, it should be borne in mind that the chip in the model is installed in the PP19 series. Due to this, the intermediate frequency parameter never exceeds 30 Hz.

USB device TDK

This USB-COM adapter is best suited for connecting receivers with an RSR30 type connector to a personal computer. The transducer in this case is used with high sensitivity. In this case, the microcircuit is installed meridional. The modulator is connected to it with an operating frequency of 28 Hz. High bandwidth in the device is provided by high-quality transistors.

It should also be noted that the deviation of the transducer is quite rare. However, this adapter still has disadvantages. First of all, they are associated with wave distortion. As a result, device synchronization can take a long time for the user.

USB-COM RS232

The USB-COM RS232 adapter is used to connect devices with RSR21 connectors. In this case, the high quality of the modulator deserves special attention. In this case, the microcircuit is used in a device of the PP21 type. Transistors in this model are installed in an analog form. They do not differ in special throughput. However, the signal response speed parameter of the presented adapter is at the level of 30 ms. This was largely achieved by installing a powerful converter.

It is able to maintain the operating frequency in the system at 23 Hz. Contacts in this case are copper. All major formats are supported by the system. The driver for the USB-COM adapter can be purchased from the manufacturer. The outer shell of the device is made entirely of PVC. Additionally, it should be noted that the limiting frequency parameter is exactly 30 Hz. In this regard, the bandwidth of the device is quite high.

Modification USB MINI8M

This COM (port USB) adapter is suitable for devices that have a connector of the RSR26 series. In particular, these models are actively used to connect receivers to personal computers. Additionally, the modification can be installed in laptops. It is very compact in size. The outputs on the microcircuit are provided by the manufacturer of the coaxial type. In terms of sensitivity, this model does not differ from other devices. Additionally, it should be noted that the operating frequency parameter is at the level of 21 Hz.

In this case, the conductivity of the resistors is not very high. As a result, the response time of the signal is on average 20 ms. The intermediate frequency index of the model is 33 Hz. The modulators in this adapter are thermo-optical. Wave distortion in them occurs quite rarely. Additionally, it should be noted that the presented adapters often suffer from elevated temperatures. They can be used at a maximum of 40 degrees.

Parameters of USB MINI8P

This USB) adapter is most often installed under various receivers. The operating frequency is exactly 25 Hz. In this case, the signal response speed is at the level of 40 ms. The converter in this case is used by the manufacturer of the non-chromatic type. Its throughput is rather weak. However, it can withstand a load of about 3 A. Due to this, stability is ensured at a good level, and the transistors in the device rarely burn out. Of the shortcomings, a sharp increase in the clock frequency should be noted. This is due to the modulator being out of sync.

Devices with controller connector

USB-COM adapter with a connector on the controller is considered quite popular today. Microcircuits for it can be selected various. As a rule, converters are installed low-frequency. This is due to the fact that the signal response speed of the models is good. Modulators for adapters of this type are used only meridional. All this leads to an increase in the limiting frequency up to 30 Hz. However, the stability of the device can be controlled by installing an amplifier on the model.

Models with a connector for a peripheral device

Adapters with a connector for a peripheral device are not very popular. First of all, they are absolutely not suitable for laptops. Additionally, they can only use microcircuits of the PP13 series. All this, ultimately, entails a number of problems. First of all, it should be noted the low parameter of the intermediate frequency at the level of 10 Hz. This is due to the lack of an input resistor on the board.

Also, problems with such models often arise due to a sharp drop in voltage. This happens when the load on the converter exceeds 3 A. However, despite all the above disadvantages, adapters with a connector at the peripheral device are still useful when it comes to connecting equipment with an RSR24 output.