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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Usually, no. If the DB-9 (more precisely, DE-9) port carries RS-232 serial data, a cable to VGA will not produce a picture. A passive cable only changes wiring; it cannot turn serial data into video. A nine-pin connector can carry legacy video on some devices, though, so a purpose-built adapter may work when the signal, pinout, and display timing are confirmed.
What “DB-9” and VGA mean
DB-9 is the familiar marketplace term for a nine-pin D-sub connector; DE-9 is the technically more precise shell designation. Neither name identifies the signal carried by the pins. Nine-pin connectors have been used for serial communications, game controllers, EGA or CGA displays, industrial equipment, and proprietary connections.
Conventional VGA uses a 15-pin, three-row high-density D-sub connector, commonly called HD-15 or DE-15. Its signals typically include analog red, green, and blue video, horizontal and vertical sync, grounds, and monitor-identification or DDC connections. The physical connector is different from a DE-9, but connector shape alone cannot establish whether an adapter is electrically compatible.
Why an RS-232 DB-9 port cannot drive a VGA monitor
- Different connector: DE-9 and VGA’s 15-pin connector have different pin counts and mating geometries.
- Different electrical signals: RS-232 uses voltage transitions to communicate digital data. VGA expects analog color channels and video timing signals.
- Different job: RS-232 connects devices such as modems, routers, PLCs, barcode readers, and industrial controllers. It does not generate framebuffer video.
A USB-to-RS-232 adapter still provides serial communications, not a display output. For example, StarTech describes this product as a USB-to-serial adapter, while its USB2VGAE3 is a separate USB-to-VGA display adapter. Those are different signal paths and product types.
#1 Best Overall
- Package Content: 1 x Serial Port Cable Cable. Before purchasing, please verify that your device is compatible with this product's specifications
- Hand:tightened screws provide a secure connection
- Length: 1.35M/4.4ft; Type: RS232 DB9 9 pin to VGA video 15 pin adapter cable
- Extends your existing DVI Dual:Link cable; The cable provides high:performance connection between PCs and flat panel displays, digital CRT displays, projectors and HDTV
- Shielded Cable and Two Ferrite Core can minimize crosstalk,suppress noise,and protect against electromagnetic interference (EMI) and radio frequency interference (RFI)
Be wary of listings titled “RS232 to VGA,” “DB9 to VGA,” or “9-pin VGA adapter.” Check the stated input and output signals, not just the title. Some larger video or KVM products have both RS-232 and VGA connectors, but those are separate interfaces; StarTech’s KVM extender manual, for example, documents separate DB9 RS-232 and DE-15 VGA connections.
How to identify the signal on a nine-pin port
- Read the label. “RS-232,” “COM,” “Serial,” “Console,” “TX/RX,” or “RS-485” points to communications, not video. “EGA,” “CGA,” “RGB,” “MON,” or “VIDEO” may indicate a display connection, but still needs verification.
- Find the exact device model and manual. Look for the connector pinout, signal names, voltage levels, analog or digital RGB type, sync format, horizontal frequency, and vertical frequency.
- Check the original cable and use. A port previously connected to a modem, console, or control system is likely serial. A cable that connected to an old monitor may carry EGA, CGA, monochrome, or proprietary video.
- Confirm pin numbering and wiring from device documentation. Do not assume a familiar PC RS-232 pinout or that a particular pin is ground.
- Compare video timing with the display’s supported input range. Correct color wiring alone is not enough if the monitor cannot lock onto the source’s scan rate or sync.
Record the make and model of both source and display, connector gender, signal names, grounds, any power pins, and the sync type before buying anything. Do not apply unknown voltages to a VGA input: incorrect wiring can damage the source or display.
Rank #2
- HOW IT WORKS: BENFEI USB to RS232 DB9 Male Serial Adapter is designed for connecting to serial devices such as DB9 equipped serial modems, ISDN Terminal Adapters, digital cameras, label writers, palm PCs, barcode scanners, PDAs etc through USB port with 1Mbps data transfer rate;
- CONNECTORS: With standard USB Type A Male to standard Male 9-pin DB9 RS-232 serial connector; Pay attention, it's not the USB to VGA(DB15) solution, unable to mirror video/audio to external montor. It's the USB to DB9 solution.
- CONDUCTOR & SHIELDING: Tinned Copper Conductor(Wire guage#24#28) and triple shielding ensure the best data transfer rate. Powered by USB port, no external power adapter required. Simple installation, plug & play after one time driver installation;
- WIDE COMPATIBILITY: USB to RS232 adapter is with Prolific PL-2303 Chipset for widest possible compatibility with Windows 11, 10, 8, 7, XP, Vista, 2000, 98, MacOS8 or higher, Linux 2.4.0 and later, and other platforms.
- 18 MONTH WARRANTY: Exclusive BENFEI Unconditional 18-month Warranty ensures long-time satisfaction of your purchase; Friendly and easy-to-reach customer service to solve your problems timely
Which signals can work with a DB-9-to-VGA connection?
| Port label or documented signal | Likely meaning | Will a generic DB-9-to-VGA cable work? |
|---|---|---|
| RS-232, COM, Serial, Console | Serial communications | No |
| RS-485 or RS-422 | Differential communications | No |
| TX, RX, GND | Serial communications | No |
| EGA | Legacy digital video | Not without a compatible, documented solution |
| CGA | Legacy digital video | Usually requires a compatible converter |
| Analog RGB or RGBHV | Video; pinout and timing still matter | Sometimes, with confirmed wiring and compatibility |
| RGBS | Analog RGB with composite sync | May require sync conversion |
| VIDEO or MON | Ambiguous | Unknown until documentation confirms the signal |
When a passive adapter is appropriate—and when it is not
A passive adapter changes connector wiring; it does not interpret or regenerate a signal. It can work when the nine-pin source is documented video, the RGB and sync pinout is known, signal levels are compatible, the sync format matches, and the VGA display accepts the source’s resolution and frequencies. Connector gender, direction, and any monitor-identification requirements must also be considered.
One documented DE-9 analog-RGB-to-VGA wiring arrangement is shown by AllPinouts. Treat it as an example for a particular arrangement—not a universal DB-9 video standard. Do not use an online pinout unless it matches the exact source equipment and signal.
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- !!Please NOTE: this is MALE RS232 to DB9 SERIAL CABLE ,Not VGA!!!It is 9 pin, NOT 15 pin!! Look carefully of the Pin is match with your device. Before ordering , please confirm the interface gender is waht you need. After receiving ,please read user manual /instruction at first and download the Driver at first from FT232 Official website or Cisco website . Customer service always online.
- Wide range of applications: USB to RS232 DB9 male serial adapter can work with your Windows (10 / 8.1 / 8 / 7 / Vista / XP), MAC or Linux system and other platforms. USB adapter is designed to connect to serial devices, such as serial modem with DB9, ISDN terminal adapter, digital camera, label writer, palm computer, barcode scanner, PDA, cash register, CNC, PLC controller, tax printer, POS, bar code scanner, label printer, etc
- High quality: ftdi usb serial,the latest ftdi chip set ensures more reliable and faster operation. USB 2.0 to RS232 male DB9 console cable will support 1Mbps date transfer rate.
- Most convenient: rs232 to usb simple installation, plug and play, COM port creation, baud rate can be changed to the required settings. USB power supply - no external power supply required.
- Exquisite design: usb-to-serial,Gold Plated USB RS232 connector and PVC cable ensure high performance and extra durability. Powered by USB port, this USB to DB9 series RS232 adapter cable is designed to fit easily into your handbag.
An active converter is needed when the source and display differ in signal format, scan rate, resolution, sync, or analog-versus-digital signaling. That may include CGA/EGA-to-VGA, TTL RGB-to-analog VGA, composite-video-to-VGA, or HDMI/DisplayPort-to-VGA. A scan converter can also regenerate timing that a monitor cannot accept. USB display adapters are a separate category: they use display hardware and software to generate video rather than converting RS-232.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Common source scenarios
PC serial port or USB-to-serial adapter
A computer’s RS-232 DB-9 port will not display video on a VGA monitor, and neither will a USB-to-serial adapter. If you need serial communication, use the appropriate serial adapter and cable. If you need a picture, use the computer’s actual video output—such as VGA, DVI, HDMI, DisplayPort, or supported USB display output—and choose a compatible video adapter if needed.
Rank #4
- VGA to DB9 signal cable, female to male, 15-pin to 9-pin, VGA three-row, RS232 serial port data cable,2Meter
- Some video devices are 9-pin, but our computer graphics cards are all 15-pin, which is the purpose of this cable. It adopts UL standard design and is suitable for connecting computers and serial port devices and transmitting signals between them.
- The wiring method of this cable: 1-1, 2-2, 3-3, 4-13, 5-14, 6-6, 7-7, 8-8, 9-10, 9-11. (You need to understand the wiring method or check the wiring method description in the video device product manual)
- Using polyethylene HDPE inner insulation, pure copper wire core + shielding, high-fidelity design, strong anti-interference ability, reduced transmission signal attenuation, and good use effect.
- Please note: This cable is compatible, not universal. Please match the interface and line, both are indispensable. Some devices may not be able to connect. The cable is absolutely good. If there is a compatibility issue, please consider it carefully before buying. Thank you for your understanding and support!!!
EGA, CGA, vintage computers, and arcade machines
A nine-pin monitor cable may be used with EGA or other legacy video, but extending that cable is not the same as converting it to VGA. StarTech lists its MXT100 DB-9 extension cable for EGA monitor cables and serial mice; that does not mean it converts EGA scan rates or signals to VGA. Vintage computers and arcade systems may output digital RGB, monochrome, composite, or unusual analog RGB. Confirm the standard and timing, then select a purpose-built converter if required.
Industrial or embedded equipment
A nine-pin port on a panel, controller, or machine could carry RGB, sync, power, control, or proprietary signals. Use the service documentation and match a converter to the exact documented input standard; do not rely on a generic product title.
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Best Value
- VGA to DB9 signal cable, female to male, 15-pin to 9-pin, VGA three-row, RS232 serial port data cable, 1.5Meter
- Some video devices are 9-pin, but our computer graphics cards are all 15-pin, which is the purpose of this cable. It adopts UL standard design and is suitable for connecting computers and serial port devices and transmitting signals between them.
- The wiring method of this cable: 1-1, 2-2, 3-3, 4-13, 5-14, 6-6, 7-7, 8-8, 9-10, 9-11. (You need to understand the wiring method or check the wiring method description in the video device product manual)
- Using polyethylene HDPE inner insulation, pure copper wire core + shielding, high-fidelity design, strong anti-interference ability, reduced transmission signal attenuation, and good use effect.
- Please note: This cable is compatible, not universal. Please match the interface and line, both are indispensable. Some devices may not be able to connect. The cable is absolutely good. If there is a compatibility issue, please consider it carefully before buying. Thank you for your understanding and support!!!
Display with a nine-pin input
A display’s DE-9 input is not automatically VGA. It might be EGA, CGA, RS-232 control, touchscreen data, or a proprietary interface. Identify the display model and consult its manual before connecting a source.
Quick Recap
Choose the right replacement connection
- DB-9 labeled RS-232: Do not buy a DB-9-to-VGA cable. For a picture, locate the source’s real video output. For serial control or configuration, use a USB-to-RS-232 adapter and the correct serial cable.
- Documented analog RGB: A passive adapter may suffice if pinout, levels, sync, and timing all match. Otherwise use an active converter.
- CGA or EGA: Confirm the exact standard and scan rates; use a purpose-built CGA/EGA-to-VGA converter when the monitor cannot accept the source directly.
- HDMI or DisplayPort source: Use a compatible active HDMI-to-VGA or DisplayPort-to-VGA adapter, not a serial DB-9 cable.
- USB source: A USB-to-VGA display adapter may work when its operating-system and workload requirements fit. StarTech’s USB2VGAE3 listing specifies VGA output and support up to 1920×1200 for supported Windows systems, and says it is not intended for graphically intensive applications. Its USB32VGAE listing specifies analog resolutions up to 2048×1152 and lists Windows 11, 10, 8/8.1, 7, Vista, and XP, with a similar workload caution. These are product-specific specifications, not universal VGA limits.
Troubleshooting a failed connection
- “No Signal”: The DB-9 may be serial, or the source may use CGA/EGA, TTL RGB, an incompatible sync format, unsupported timing, or a different pinout. A powered converter may be required.
- Scrambled, rolling, or unstable image: Suspect sync or scan-rate incompatibility. Passive wiring cannot change frequency or regenerate sync.
- Monochrome image or wrong colors: Check whether the source is monochrome, a color channel or ground is missing, or the pin numbering and RGB standard differ.
- Adapter heats up or source shuts down: Disconnect immediately. Wiring may short power to ground or connect incompatible outputs.
- Listing says “RS-232-to-VGA”: Verify whether RS-232 is just a control channel on a larger product. Serial data itself is not a video signal.
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