entranceStraight-through modem cable. Zero modem cable (RS232) wiring
Almost every computer is equipped with at least one serial asynchronous adapter. Usually it is a separate card that plugs into a computer expansion slot or is located directly on the motherboard (system) board.
Serial asynchronous adapter is also called asynchronous RS-232-C adapter, or RS-232-C port. Each asynchronous adapter usually contains several RS-232-C ports through which various external devices can be connected to the computer. Each such port corresponds to several registers through which the program gains access to it, and a specific IRQ number to signal the computer about a change in the port state. When the BIOS executes the boot procedure, all RS-232-C ports are assigned logical names COM1 - COM4 (COM port number 1 - 4).
7.1. What are asynchronous I / O ports for?
The serial port is widely used. That's far from full list applications:
- mouse connection;
- connection of plotters (plotters), scanners, printers, digitizers;
- communication of two computers through serial ports using a special cable (null modem);
- connection of modems for data transmission over telephone lines;
- connection to the network of personal computers.
7.2. What are the technical parameters of the RS-232-C interface
When transmitting data over long distances without the use of special equipment, due to interference caused by electromagnetic fields, errors may occur. As a result, there are restrictions on the length of the connecting cable between devices connected using the RS-232-C interface.
The length limitation for the RS-232-C connecting cable is 15.24 meters. In practice, however, this distance can be much greater. It directly depends on the baud rate. According to McNamara (Technical Aspects of Data Communications, Digital Press, 1982), the following values are defined:
The voltage levels on the connector lines are -15 ..- 3 volts for a logical zero, +3 .. + 15 volts for a logical unit. The interval from -3 to +3 volts corresponds to an undefined value.
If you connect external devices to the RS-232-C interface connector (and also when connecting two computers with a null modem), first turn off external device and the computer, and discharge any static electricity (by connecting to ground). Otherwise, the asynchronous adapter could be damaged.
7.3. What are the asynchronous adapters
The asynchronous serial adapter uses a universal asynchronous transceiver microcircuit - UART 8250. UART 8250 microcircuit in its original form was used only in old models of asynchronous serial adapters. Currently, more modern transceiver microcircuits are used - UART 16450, 16550 and 16550A.
These UARTs, manufactured by new technology, allow to achieve a higher data exchange rate, and also have new hardware capabilities. Let's list the main characteristics of various UART microcircuits, and therefore of the asynchronous serial adapters on which these microcircuits are installed:
| Chip type UART | Specifications |
| 8250 (8250-B) | Used on the first models of IBM PC / XT, has low performance |
| 16450 / (8250-A) | Microcircuit 16450 almost completely corresponds to 8250. It eliminates errors in the interrupt enable register and adds the ability to transfer the OUT2 line to a high-impedance state |
| 16550 | Added the possibility of internal buffering of transmitted and received data. The buffers are queued (FIFO). Due to an error in the microcircuit, it is better not to use the buffering feature - you can lose individual characters. In general, the 16550 chip is faster than the 16450. The 16550 chip allows multiple DMA channels to be used |
| 16550A (16550AN) | According to its characteristics, it corresponds to 16550, but errors in the FIFO implementation have been corrected. This microcircuit allows programs to use multiple DMA channels. If you want to operate at speeds higher than 9600 baud, you should use an asynchronous serial adapter containing this particular microcircuit. |
7.4. What is a null modem
If you have two computers equipped with asynchronous serial adapters, you can connect them using a null modem male. The null modem cable is connected to the serial adapter ports of the computers to be connected.
With the help of special software through a null modem cable, you can quickly copy data between computers. If computers are not connected to a local network and you need to rewrite a large amount of information from one computer to another, using a null modem is the best solution.
A null modem is a fairly simple device. It consists of two connectors and a cable connected in a specific way. If you have two mating connectors from the asynchronous adapter ports and a multicore cable handy, you can easily make a null modem yourself.
Figure 7.1 shows two null modem circuits using two DB25 connectors.
Rice. 7.1. Null modem circuits
There are two types of serial adapter port connectors, DB9 and DB25. These connectors differ in the number and purpose of the pins. A DB9 connector has 9 and a DB25 connector has 25 pins. Despite the different number of conclusions, their functionality are the same.
If you assembled a null modem according to the diagram above, and the serial adapter has only a 9-pin connector free, you can use a special adapter (see Fig. 7.2).
Rice. 7.2. Adapters DB25 - DB9
7.5. How to link computers over an asynchronous port
If you have two or more computers at your disposal, then you can organize the exchange of data between them without using floppies and without installing network adapters.
To do this, you need to connect the ports of the asynchronous serial adapters of the computers using a null modem cable. After that, with the help of special software, you can access from one computer, called a working one, to the disks of another, called a server. In this case, you can work only at a working computer, but you get full access to the server's disk subsystem.
You can use Norton Commander or FastLynx as the software used to communicate between computers over the ports on the asynchronous serial adapter. Operating system MS-DOS version 6.0 includes its own means of organizing communication between computers via a null-modem.
Below we will look at using Norton Commander and MS-DOS 6.0 Tools.
Using Norton Commander
The most simple program which can be used to directly link two computers via null modem cable, is Norton Commander. With this program, you can exchange files between computers, while you can work on only one computer.
Using a null modem and asynchronous adapters can be very useful if you need to copy a large amount of information from one computer to another. In this case, if the computers are not in local network, the process of copying via floppy disks can take several hours. By using a null modem, you can significantly speed up the copying process. Below we will provide a quick guide on how to link two computers via asynchronous serial adapters.
First, turn off the power of both computers and connect them through the asynchronous serial ports (COM ports) with a null modem cable. Then turn on the computers and start Norton Commander on both computers.
For each computer, select linK from the Left or Right menu. The Commander Link dialog box appears on the screen (see Fig. 7.3).
Rice. 7.3. Commander Link Dialog Box
Then you need to select the operating mode - "Master" (work computer) or "Slave" (server), and also define the serial port that you will use for the connection - COM1 or COM2. This is the port that the null modem cable must be connected to.
For one of the computers to be connected, select the "Master" mode, and for the other - "Slave". In this case, you can only work on a computer in the "Master" mode.
The Turbo Mode switch, located on the Commander Link dialog box, sets increased speed data exchange. Turbo Mode must be installed on both computers at the same time.
With Norton Commander, you can do the following:
- copy and move files from one computer to another;
- delete, create new files on the server, change file attributes;
- create, delete directories on the server.
With Norton Commander, you cannot perform basic operations on server disks from your main computer, such as browsing a directory tree and launching programs.
If you are not satisfied with the capabilities of Norton Commander, use MS-DOS 6.0 or connect your computers with a local area network.
Using MS-DOS Tools
The distribution kit of the operating system MS-DOS version 6.0 includes software for organizing data exchange between computers through the ports of an asynchronous adapter or through parallel ports. These include the Interlnk driver and the Intersvr program.
With the Interlnk driver and Intersvr software, you can get full access from your work computer to the disks and printers connected to the server. At the same time, new devices appear on the working computer through which you can access the disks and parallel ports of the server.
Thus, new disks as well as parallel ports appear on the working computer. In terms of their properties, with the exception of speed, they fully correspond to local drives and parallel ports of the computer. You can freely write and read files from these disks, run programs. If a printer is connected to the server, then you can print a document on it directly from your work computer.
Consider the process of connecting computers through the ports of an asynchronous adapter.
To connect two computers, you need to connect them using a null modem. Then include the Interlnk driver in the CONFIG.SYS file of the working computer:
DEVICE = C: DOSINTERLNK.EXEThe n parameter defines the number of server disks that you want to use from the work computer. If you do not set this parameter, only three drives will be available:
DEVICE = C: DOSINTERLNK.EXEThen run the Intersvr program on the server:
INTERSVRNow logical drives the server and its printer ports are accessible from your work computer.
Rice. 7.4. Server
In our case, three new disks with the names I :, J: and K: appeared on the working computer, as well as a new parallel (printer) port LPT2.
Through drives I: and J: you can access drives A: and B: located on the server, through drive K: to the hard drive C: of the server, and through the parallel port LPT2, you can access the device (printer) connected to parallel port LPT1 on the server.
Problems with the "firmware" of receivers. Lack of COM port. Laptop use
Most "old" computers and laptops purchased more than 5 years ago always had several COM ports (RS-232). At least there has always been 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 with connecting the receiver to the computer for "firmware". It was enough just to connect, run the program to update the receiver's software and calmly do everything necessary.
In modern computers, the RS-232 connector is often absent. This is where problems arise, often very unpleasant. In most receivers there is no other way of "flashing" 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 transmission standard. They go to this in order to save energy of the battery charge. If the manufacturer of the receiver was technically scrupulous and accurate, then a special microcircuit for the "COM" port will be installed in the receiver. Thanks to this microcircuit, the receiver will work with both a laptop and a computer. But the installation of a microcircuit increases the total cost of the product, and lately, manufacturers are saving even on these trifles! 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 additional module with "COM" ports. This board installed in the computer is called "PIC-COM" or simply "COM port board".
Rice. 2. PCI card for a computer with two "COM" ports
If you are not good at computers and have never dealt with the installation of additional equipment in a computer before, then contact a specialist! Otherwise, you can "kill" expensive equipment.
After installing the card into 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: it is not the same standard and size. There are two ways to solve this problem: expensive, but of 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 could not get this board, even on order.
Rice. 3. Board for laptop with "COM" port
And here's the catch: "old" and "new" laptops have 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". In almost all modern models computers have a "USB" output, at least two, or even all eight! Various USB to COM converters are available on the market.
Rice. 4. Converter "USB - COM"
Rice. 5. Scheme of the converter "USB - COM"
How to solder the 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 will only match the RX and TX signals.
All other modem signals are inactive.
For most devices without hardware flow control, this is more than enough.
With Pilot VAF / MAF converters, the adapter works 100%
Go!
To assemble you need the following parts:
1. PL2303HX (USB-USART bridge from Prolific) -1pc.
2.MAX232CSE (UART-RS232) -1pc.
3. Quartz 12.00 MHz-1 pc.
4. Capacitors 10 nF (smd1206) -2 pcs.
5. Capacitors 1 uF (smd1206) -6 pcs.
6. Resistors 27 Ohm (smd1206) -2 pcs.
7. Resistors 1.5KΩ (smd1206) -1pc.
8. Connector mini-USB -1 pc.
9. DB-9 male connector - 1 pc.
10. Foil textolite for board 48 * 22mm - 1pc
Adapter circuit
Printed circuit board
Schematic files and seals in the format Eagle PCB Editor can be downloaded from this link
Build 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:
To prevent oxidation, the board can be blown out with polyurethane varnish or any quick-drying car varnish that is at hand.
Next, we connect this device to USB port computer.
Windows will detect a new device and ask for a driver
We go to the site of the prolific and download the most latest version firewood
At the time of this writing, the latest driver was this one.
After feeding the driver to Windows, a new Prolific COM port should appear in the system: 
Now you need to check the functionality of the adapter
To do this, on the adapter in the COM port connector, use a screwdriver or a wire to close pins 2 and 3 together (on the connector itself, numbers with contact numbers are usually knocked out - 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 whist and seven! Therefore, you will have to go to Google / Yandex to download the hyperterminal or any of its analogs.
We select our new som-port in the connection settings:
Now we launch the connection, select English layout and try to print something.
The symbols of the keys pressed should appear on the screen:
If the letters do not appear, then check the installation
That's all!
Now it remains to remove the jumper from contacts 2-3 and you can use the adapter for its intended purpose.
Those. the input of such a "converter" is connected to a free "USB" connector of the laptop, a driver (control program) is installed from the disk from the kit, and system settings a virtual COM port appears with the assigned serial number.
How to solder the USB-COM adapter yourself. Option - 2
| Picture 1.General form |
 |
The proposed block in assembled form allows you to implement the principle: buy - connect. 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 to a personal computer various devices, as well as modems and programmers.
Specifications
Supply voltage from USB port: 5 V.
Consumption current: 20 mA.
RS232C communication 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.
Instructions: 1.
Design
Structurally, the adapter is made on a double-sided printed circuit board made of foil-clad fiberglass, protected by a transparent heat-shrinkable tube.
The adapter provides all modem signals: DSR, DTR, RTS, CTS, RI, DCD, as well as the main signals RXD and TXD.
Figure 2. Electrical schematic diagram
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Figure 3. View printed circuit board from the side of parts
Block operation description
Principled electrical circuit given on pic 2.
The central part of the device is a CP2102 microcontroller manufactured by SILICON LABORATORIES. A MAX3243 converter manufactured by Texas Instruments is used as a level driver microcircuit. The adapter provides all modem signals: DSR, DTR, RTS, CTS, RI, DCD, as well as the main signals RXD and TXD.
Installing the device in the OSTo install drivers for your computer, you must first download the driver appropriate for your operating system.
Next, install the driver on your personal computer. Connect 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 device is ready 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 only experienced users! You can download
PERFORMANCE CHECK BM8050 WITHOUT EXTERNAL EQUIPMENT
To check the transmission and reception of all necessary modem signals according to the connection of the COM device.
Place 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, for which go to Start --- Customization --- Panel Management --- System --- Equipment --- Dispatcher Devices --- Ports(COM and LPT) --- Silicon Labs CP210x USB to UART Bridge (COM1).
Run standard application HiperTerminal for Windows from Start --- Programs --- Standard --- Connection--- HiperTerminal.
Stop the running connection, if it is active, for which click the Call --- Stop above.
See which port is used by the program to communicate with the device, for which enter 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 the selected flow control "Hardware" in the program, for which click the button in the center "Configure" and in the lower window "Flow control" select "Hardware".
Exit the program settings, for which click OK, OK again.
Type the text "Text" in the HiperTerminal software, and the text "Text" is printed on the screen, which confirms that the device is working.
Remove the jumpers from contacts 2-3, 4-6, 7-8 of the BM8050 COM-connector.
Type the text "Text" in the HiperTerminal software, and 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 a too large number to the virtual port, for example, "25". And the program for "flashing" the receiver allows you to work with port numbers from one to four. Secondly, not all USB-COM converters can work with the firmware and the receiver itself. The reason is that equipment manufacturers have made their products and programs for them 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 piece of equipment, but not with the other.
If the first problem is fixed by changing the port number in the OS settings, then the problem of hardware, program and converter compatibility cannot be fixed.
To change the number assigned to the asset, 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 opens. 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" construction.
Rice. 15.8. Configuring the selected port
In the window that appears, select the "Port Settings" tab. In the line "Speed" select "115200", then click on the "Advanced" button.
Rice. 15.9. Configuring Port Parameters
At the bottom of the window that opens, find the "COM port number" tab.
Rice. 16. Changing the COM port number
Click on the tab and select the required COM port number.
Note that some of the port numbers may be occupied by existing hardware, such as an internal modem. You cannot use one port at a time!
After completing the settings, click "OK" to save the changes and completely exit the settings mode by closing everything earlier open windows... Then restart your computer to make the necessary changes. If you changed the "COM" number of the "USB-COM" port of the converter, then you just need to 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 - RUB 300
Description A cable for connecting devices with a serial interface (RS-232) to the USB port.
Cable or adapter connectors COM25M, COM9M, USB A
Compatibility
USB 1.1 / 2.0 compliant
Supports Windows 2000, Windows XP
Other
Cable length 1 meter
Logistics
Package dimensions (measured in NIKS) 21.5 x 14.5 x 4.1 cm
Gross weight (measured in NIKS) 0.136 kg
TRENDnet Adapter Cable 
Price - RUB 500
The main
Brand TRENDnet
Model TU-S9
Equipment type Adapter cable
Diameter 28/24 AWG
Performance parameters
Data transfer rate 500 Kbps
Powered by USB port
Power Consumption 500mA - Maximum
Compatibility
System Requirements RAM 64 MB
Supports Windows ME, Windows 2000, Windows XP
Other
RoHS Compliance
Cable length 0.6 meters
Weight 75 grams
Working temperature 0 ~ 40 ° C
Package dimensions (measured in NICS) 23 x 16.8 x 4.6 cm
Gross weight (measured in NIKS) 0.135 kg
External sources information
Link to the manufacturer's website www.trendnet.com
Adapter - USB-COM (RS-232) adapter
Price - RUB 1,500
The adapter is intended for the use of devices and adapters designed to be connected via the Com (RS232) port, for example, this is very important when using modern computers that have only USB, in this case, with this adapter you can use modern computers and laptops together with our devices and adapters, such as BMW Scanner, Mercedes Scanner, Scanmatik, etc.
Car service equipment, autodiagnostics, diagnostic equipment, auto diagnostics, car scanner, autoscanner, diagnostic post, chip tuning, equipment for autodiagnostics Carbrain, UNISCAN, ADP-504, KKL-USB, KKL-COM, BMW scanner, Opel scanner, BMW 1.3 .6, Automan, Opel scanner, BMW scanner, motor tester, gas analyzer, engine diagnostics, instrument panel 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 null modem cable.
- Retail value 100 rub.
- Type A-A
- Length: 1.5m
But for the rest you need " inverted" null modem cable.
- Retail price RUB 155.00
- Connector type: DB9 F to DB9 F
- Length: 1.8 m
or an adapter like this:
STLab U-350 (RTL) Adapter COM 9M -> USB AM
Price - RUB 350
The 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 the port USB computer.
Equipment type Adapter cable
Connectors for cable or adapter COM9M, USB A
Built-in USB connector Yes
Performance parameters
Baud rate 115200 bps
USB 1.1 interface
Powered by USB port
Supports Windows 2000, Windows ME, Windows XP, Windows Vista, Windows 2003 Server
Package dimensions (measured in NICS) 17 x 13 x 3.2 cm
Gross weight (measured in NIKS) 0.077 kg
External sources of information Link to the manufacturer's website
Null modem connection. From my own experience.
Why else would you need such a connection? For example, a friend came to you and wants to fill you up with a rocket launcher a couple of times. Or you have two computers at home (and this is not so rare) and you want to have access to the Internet from both computers, while having one modem. Or maybe you need to transfer several large files from one computer to another.
For such a connection, it is enough to buy a so-called null-modem cable. Cables for COM and LPT ports cost about the same ($ 3 - $ 6), the data transfer rate is also about the same. The advantage of such a connection is its low cost and the absence of additional equipment. Disadvantages: short distance (up to 5 m) between computers; low data transfer rate; one-way control of data exchange.
Anyone who remembers DOOM1 at work or at the institute will probably remember the so-called "lanyard" - 3 wires attached somehow to the COM ports of two three-ruble chips (Intel 80386). This simple device allowed you to play against each other or together against monsters, which introduced a new element of thrill into the game. WITH the advent of Windows and games requiring communication using IPX, TCP / IP pro this device forgot. But in vain. Everything is not so difficult, and for the house it is a very attractive solution, and its name is NULL-MODEM. So, null modems are of two types: for COM (serial) ports and for LPT (parallel) ports. The first type connects to the same type of ports as a regular modem (there are usually 2 of them), the second to a printer port (which is not very convenient if you have a printer).
A null-modem connection for COM ports is convenient because, as a rule, one COM port is free on a computer. The disadvantage is that the baud rate is only 115200 bps. Only 2-3 times faster than good connection with the Internet. At this speed, 1 megabyte of data is transferred a little over a minute. Generally, if you decide to use a null modem cable for the COM ports, then it is better to buy it. The fact is that there are 2 types of COM ports: DB-25 (wide, 25 pins) and DB-9 (narrow, 9 pins). You can purchase a universal null-modem cable at a radio store or in a company that sells components for computers. Each end has a pair of connectors - one for DB-25 and one for DB-9. If you decide to solder it yourself, then use the diagram below:
|
|
|
I do not recommend trying to plug the cable into the connectors while at least one of the computers is powered on: you can burn the port. Well, if you do it, then first you need to touch the connector housing. If you connect without shutting down the computer, then you still have to reboot to initialize the ports.
What else I noticed: on the laptop there was an English Norton, and I had a Russian one, the communication programs were respectively called telnet.exe and telemax.exe. When transferring 2 MB of information, about 300 errors were typed. When I installed the same Russian version on two machines, the number of errors dropped to zero. Don't be intimidated by the inscription in the upper right corner OFFLINE - this is how it should be. You can work with Norton from both DOS and Windows. I tested it only under Windows 98. True, the communication program window must be active, otherwise the speed drops dramatically and the number of errors increases, but the connection is not interrupted.
It doesn't matter which connectors to use: 9 and 25, 9 and 9 or 25 and 25 pins, the main thing is to indicate in the Telemax program from the Norton set of programs that you need to use such and such a port. If the computer was turned on, then you need to reboot after connecting. For a long time I could not find Norton Commander on the Internet - only broken links came across. Therefore, I will lay out the Norton shell with the Telemax program for download, we will need it. I gave the view of its shell above. For the convenience of downloading and transferring on a floppy disk, I pretty much cleaned up the folder, leaving Norton Commander and Telemax, in fact. The default settings do not need to be changed, but be sure to check the port where the wire is connected. I can say more - if there is no connection and not crooked hands - the port is incorrect. After changing the port, you need to save the settings so that they will be the next time the program is loaded. To check, run Telemax on two machines and send the file via ZModem with one. On the other, a download window opens automatically. When the download is complete, a beep will sound.
Additional Information:
Bezsmertny V.S.
admin www.shems.h1.ru
Ukraine, Kiev
Updates to software its equipment, errors in it are corrected, as well as performance is improved or some new functions are added.
In order to update the device's firmware, you first need to download it to your personal computer, and then connect the receiver to the PC and restart the program. A null modem cable is used to connect the computer to the satellite receiver. If you do not have such an interface, you can buy it in computer stores, however, these products are not always there. In any case, you have a choice: look for a ready-made solution or make a null-modem cable yourself. The latter option is much cheaper.
How to make a null modem
To manufacture it, we need a four-core cable (the length is determined by the user) and two connectors of the RS 232 type ("female"). These connectors can be found in any radio store, they are very popular, since they are present in almost every personal computer as a COM port. It can serve as a cable To do this, we twist each of the cores together and we get four conductors. Next, you need to unsolder the connectors. In this case, it is necessary to prevent accidental short circuiting, as this will lead to equipment failure. Such a null modem cable will work stably with a wire length of up to 50 meters.
This instruction is not mandatory, but it has been proven in practice:
2. The connection of the connector housings is necessary to relieve stress, since the housing touches the device. Otherwise, there is a risk of burning the COM interface on the computer or receiver. This connection is optional if all equipment is grounded.
3. Preferably used as it works best.
4. All signals use only three pins.
5. In some receiving devices there is no MAX232 microcircuit (it is assumed that it will be in an external adapter). In such devices, four outputs are used on the COM port of the receiver, but the same three contacts are used at the output of the adapter. Therefore, before connecting a null-modem cable, you need to study the documentation for your device in detail, perhaps first you need to connect an adapter.
6. In some tuners, pins 2 and 3 on the connector are reversed. In this case, you will need a straight-through cable, not a crossover cable. In order to determine what type of connector is on your receiver, you should study the documentation for it.
Wiring the null modem RS232 cable
In the COM interface, only three contacts and the connector body should be soldered. In such a cable, you must use 2, 3 and 5 pins. In the straight version of the null-modem cable, these pins are soldered in the same way in both connectors, and in the crossover 2 and 3 are swapped.
Zero modem cable is a very useful thing in the satellite industry. Primarily for firmware satellite receivers... But it is not always possible to buy it, so you have to do it yourself.
As I already said 0-modem cable it is useful to us first of all for reflashing satellite receivers. And if you can use a short one for this, which is easier to buy, then for cardsharing through a computer you almost always need a long or very long one (made up to 15 m). And it's better to solder this one yourself. Moreover, it is done quite easily.
How to do it yourself null modem cable (RS232) cord for firmware tuner with your own hands?
We will need two DB-9F connectors, a soldering iron, solder, a twisted-pair cable, which suits me just right (you can have another one at hand, the telephone is normal), circuits and skillful hands.
There are several connection options, but most often you need a three-pin cable. Well, if this does not work, then we make a full one for all contacts in accordance with the pictures below.
A non-zero modem cable is almost always suitable. But he also has varieties when his contacts go
Contacts 2 - 2 and 3 - 3, 5-5 direct
Pins 2 - 3 and 3 - 2, 5 - 5 not direct
It is the latter that is not straightforward that fits most often.
The wiring of the rs-232 com port in satellite receivers can look like "dad" and "mom".
“Nurses” are much more common, so I advise you to do with two “mothers” at the ends.
Precisely indirect null modem cable with two mothers, and with right-to-left calculation, suitable for flashing most satellite receivers, or for sharing.