Serial Cable Adapter
Posted on by admin
Add to cart StarTech USB C to Serial Adapter, with COM Port Retention, USB C to DB9 Cable or RS232 Cable (ICUSB232PROC) StarTech 4 Port PCI Express PCIe SuperSpeed USB 3.0 Controller Card Adapter with SATA Power - Low Profile. Serial Cables is your one-stop SAS, SATA, Fiber cable and adapter store for all your MiniSAS, IPass, SAS, Fiber Optic, Infiniband, cable, connector, adapter, and accessory interconnectivity needs - everything you need in one site! Easy to operate, simply plug the serial cable or serial adapter into a PC or Mac. They generally plug and play with no drivers to install for optimum performance and data transmission. Many have gold-plated connectors that enhance signal conduction and cable longevity. Find well known brands, including Belkin, C2G, Keyspan, StarTech and Tripp Lite. The Sabrent USB to Serial SBT-USC1M converter is the perfect solution for transferring data from a PDA or digital camera. The USB to DB9 provides a connection between an available USB port and the more traditional RS-232 serial port found on many devices.
Serial; Crossover or 'Null Modem' vs. Straight Through Serial Cable; Crossover or 'Null Modem' vs. Straight Through Serial Cable. The RS-232 specification defines two types of serial devices, DTE and DCE. DTE normally refers to the serial port on a PC or terminal, while DCE refers to a modem or other type of communications device. Yat (Yet Another Terminal), Serial COM terminal program: YAT.zip: 1.04MB: Serial COM Player: This software records and plays back serial data from your computer's serial ports: Serial Player.zip.
A null modem adapter
Null modem is a communication method to directly connect two DTEs (computer, terminal, printer, etc.) using an RS-232serial cable. The name stems from the historical use of RS-232 cables to connect two teleprinter devices or two modems in order to communicate with one another; null modem communication refers to using a crossed-over RS-232 cable to connect the teleprinters directly to one another without the modems. It is also used to serially connect a computer to a printer, since both are DTE, and is known as a Printer Cable.
The RS-232 standard is asymmetric as to the definitions of the two ends of the communications link, assuming that one end is a DTE and the other is a DCE, e.g. a modem. With a null modem connection the transmit and receive lines are crosslinked. Depending on the purpose, sometimes also one or more handshake lines are crosslinked. Several wiring layouts are in use because the null modem connection is not covered by the RS-232 standard.
- 2Cables and adapters
- 4Types of null modem
Origins[edit]
Originally, the RS-232 standard was developed and used for teleprinter machines which could communicate with each other over phone lines. Each teleprinter would be physically connected to its modem via an RS-232 connection and the modems could call each other to establish a remote connection between the teleprinters. If a user wished to connect two teleprinters directly without modems (null modem) then they would crosslink the connections. The term null modem may also refer to the cable or adapter itself as well as the connection method.[1] Null modem cables were a popular method for transferring data between the early personal computers from the 1980s to the early 1990s.
Cables and adapters[edit]
A null modem cable
A null modem cable is a RS-232 serial cable where the transmit and receive lines are crosslinked. In some cables there are also handshake lines crosslinked. In many situations a straight-through serial cable is used, together with a null modem adapter. The adapter contains the necessary crosslinks between the signals.[2][3]
Wiring diagrams[edit]
DB-25 null modem wiring diagram
DE-9 null modem wiring diagram
Below is a very common wiring diagram for a null modem cable to interconnect two DTEs (e.g. two PCs) providing full handshaking, which works with software relying on proper assertion of the Data Carrier Detect (DCD) signal:[2]
| One side | Signal direction | Other side | |||||
|---|---|---|---|---|---|---|---|
| Signal and abbreviations | DB-25 pin | DE-9 pin | DE-9 pin | DB-25 pin | Signal | ||
| Frame Ground | FG | 1 | N/A | Common | N/A | 1 | FG |
| Transmitted Data | TxD, TD | 2 | 3 | → | 2 | 3 | RxD |
| Received Data | RxD, RD | 3 | 2 | ← | 3 | 2 | TxD |
| Request To Send | RTS | 4 | 7 | → | 8 | 5 | CTS |
| Clear To Send | CTS | 5 | 8 | ← | 7 | 4 | RTS |
| Signal Ground | SG | 7 | 5 | Common | 5 | 7 | SG |
| Data Set Ready | DSR | 6 | 6 | ← | 4 | 20 | DTR |
| Data Carrier Detect | DCD, CD | 8 | 1 | ||||
| Data Terminal Ready | DTR | 20 | 4 | → | 1 | 8 | DCD |
| 6 | 6 | DSR | |||||
Applications[edit]
The original application of a null modem was to connect two teleprinter terminals directly without using modems. As the RS-232 standard was adopted by other types of equipment, designers needed to decide whether their devices would have DTE-like or DCE-like interfaces. When an application required that two DTEs (or two DCEs) needed to communicate with each other, then a null modem was necessary.[4]
Null modems were commonly used for file transfer between computers, or remote operation. Under the Microsoft Windowsoperating system, the direct cable connection can be used over a null modem connection. The later versions of MS-DOS were shipped with the InterLnk program. Both pieces of software allow the mapping of a hard disk on one computer as a network drive on the other computer. No Ethernet hardware (such as a network interface card or a modem) is required for this.[5] On the Commodore Amiga system, a null modem connection was a common way of playing multiplayer games between two machines.
The popularity and availability of faster information exchange systems such as Ethernet made the use of null modem cables less common. In modern systems, such a cable can still be useful for kernel mode development, since it allows the user to remotely debug a kernel with a minimum of device drivers and code (a serial driver mainly consists of two FIFO buffers and an interrupt service routine). KGDB for Linux, ddb for BSD, and WinDbg or KD for Windows can be used to remotely debug systems, for example. This can also provide a serial console through which the in-kernel debugger can be dropped to in case of kernel panics, in which case the local monitor and keyboard may not be usable anymore (the GUI reserves those resources and dropping to the debugger in the case of a panic won't free them).
Another context where these cables can be useful is when administering 'headless' devices providing a serial administration console (i.e. managed switches, rackmount server units, and various embedded systems). An example of embedded systems that widely use null modems for remote monitoring include RTUs, device controllers, and smart sensing devices. These devices tend to reside in close proximity and lend themselves to short run serial communication through protocols such as DNP3, Modbus, and other IEC variants. The Electric, Oil, Gas, and Water Utilities are slow to respond to newer networking technologies which may be due to large investments in capital equipment that has useful service life measured in decades. Serial ports and null modem cables are still widely used in these industries with Ethernet just slowly becoming a widely available option.
Types of null modem[edit]
Connecting two DTE devices together requires a null modem that acts as a DCE between the devices by swapping the corresponding signals (TD-RD, DTR-DSR, and RTS-CTS). This can be done with a separate device and two cables, or using a cable wired to do this. If devices require Carrier Detect, it can be simulated by connecting DSR and DCD internally in the connector, thus obtaining CD from the remote DTR signal. One feature of the Yost standard is that a null modem cable is a 'rollover cable' that just reverses pins 1 through 8 on one end to 8 through 1 on the other end.[1]
No hardware handshaking[edit]
Usb Serial Adapter Cable
Wiring pinouts for DB-25 (left) and DE-9 (right) connectors
The simplest type of serial cable has no hardware handshaking. This cable has only the data and signal ground wires connected. All of the other pins have no connection. With this type of cable flow control has to be implemented in the software. The use of this cable is restricted to>
Wiring pinouts for DB-25 (left) and DE-9 (right) connectors
Because of the compatibility issues and potential problems with a simple null modem cable, a solution was developed to trick the software into thinking there was handshaking available. However, the cable pin out merely loops back, and does not physically support the hardware flow control.[1]
This cable could be used with more software but it had no actual enhancements over its predecessor. The software would work thinking it had hardware flow control but could suddenly stop when higher speeds were reached and with no identifiable reason.
Partial handshaking[edit]
Wiring pinouts for DB-25 (left) and DE-9 (right) connectors
In this cable the flow control lines are still looped back to the device. However, they are done so in a way that still permits Request To Send (RTS) and Clear To Send (CTS) flow control but has no actual functionality. The only way the flow control signal would reach the other device is if the opposite device checked for a Carrier Detect (CD) signal (at pin 1 on a DE-9 cable and pin 8 on a DB-25 cable). As a result, only specially designed software could make use of this partial handshaking. Software flow control still worked with this cable.[1]
Full handshaking[edit]
Wiring pinouts for DB-25 (left) and DE-9 (right) connectors
This cable is incompatible with the previous types of cables' hardware flow control, due to a crossing of its RTS/CTS pins. With suitable software, the cable is capable of much higher speeds than its predecessors. It also supports software flow control.[1]
Female Serial Cable Adapter
Virtual null modem[edit]
A virtual null modem is a communication method to connect two computer applications directly using a virtual serial port. Unlike a null modem cable, a virtual null modem is a software solution which emulates a hardware null modem within the computer.[6][7] All features of a hardware null modem are available in a virtual null modem as well. There are some advantages to this:
- Higher transmission speed of serial data, limited only by computer performance and network speed
- Virtual connections over local network or Internet, mitigating cable length restrictions
- Virtually unlimited number of virtual connections
- No need for a serial cable
- The computer's physical serial ports remain free
For instance, DOSBox has allowed older DOS games to use virtual null modems.
100% Free Data Recovery Software for Windows to get back deleted or lost files from any kind of storage media, including BitLocker encrypted partition. FREEWARE No hidden fee, 100% free data recovery software download for Windows 10 8 7 from only official site of iCare to recover deleted files from internal external hard drive usb flash drive memory sd card cellphone camera and there is no trick in the free recovery which is. ICare Data Recovery Free can recover permanently deleted/erased files from Windows 10/8/7/Vista/XP. It can recover most often used files like word/documents, emails, videos, even audio files from PC hard drive or external usb disk, memory card/usb drive, etc. Free sd recovery software download. If your SD memory card has stopped working, try Amazing SD Memory Card recovery software and recover photos, videos and other files from it.It can recover deleted files from memory SD cards of. 7-Data Recovery is a user-friendly and powerful software capable of recovering deleted, damaged, and disappeared files. 7 Data Recovery is fixes: accidental file deletion, partition errors, corrupt iPhone file retrieval, SD card issues, and fixing hard drives that stopped booting.
Another common example consists of Unix pseudoterminals (pty) which present a standard tty interface to user applications, including virtual serial controls. Two such ptys may easily be linked together by an application to form a virtual null modem communication path.
See also[edit]
References[edit]
- ^ abcdefLammert Bies. 'RS232 serial null modem cable wiring and tutorial'. lammertbies.nl. Retrieved 2013-12-26.
- ^ ab'Null Modem'. nullmodem.com. 2008-11-07. Retrieved 2013-12-26.
- ^'Nullmodem (9-9) - HwB'. hardwarebook.info. 2006-12-27. Retrieved 2013-12-26.
- ^'ADTPro - ADTPro Serial Cabling'. sourceforge.net. 2011-01-25. Retrieved 2013-12-26.
- ^'MS-DOS External commands - INTERLNK'. angelfire.com. Retrieved 2013-12-26.
- ^'Null-modem emulator Download Null-modem emulator software for free at'. sourceforge.net. Retrieved 2013-12-26.
- ^'BerliOS Developer: Project Summary - N8VB_vCOM Virtual Null Modem Cable'. berlios.de. 2005-07-15. Archived from the original on 2013-12-26. Retrieved 2013-12-26.
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Null_modem&oldid=917569724'
- USB Type a Male to Ps/2 Ps2 Female Cable Keyboard Mouse Adapter ConverterTotal Ratings 20,100% agree - Would recommend
- for HP Canon Dell Brother Printer Scanner Cable Cord USB 2.0 A-b 6ft 5 600Total Ratings 19,100% agree - Would recommend
- USB 2.0 to Ieee-1284 36 Pin Parallel Printer Connector Adapter Cord CableTotal Ratings 19,87% agree - Would recommend
- Monoprice USB to PS 2 Mouse Keyboard Dual Converter Adapter 10934Total Ratings 15,100% agree - Would recommend
- 1.6ft USB to Rs422 Rs485 Adapter Converter Cable With FTDI ChipTotal Ratings 9,100% agree - Would recommend
- USB to IEEE 1284 DB25 25-Pin Parallel Printer Female Adapter Cable CordTotal Ratings 57,92% agree - Would recommend
- Rs232 Rs-232 Serial to USB 2.0 Pl2303 Cable Adapter Converter for Win 7 8 10Total Ratings 36,87% agree - Good quality
- Generic Ps/2 Ps2 to USB Male Converter Adapter Cable for Keyboard and MouseTotal Ratings 31,96% agree - Would recommend