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USB to RS232 Serial Adapter

ADP-USB-RS232

Gives a modern laptop a real serial port. Works on Windows 8, 10 and 11.

Type: Converter
Connectors: USB-A / DB9

In-depth technical details

USB-A carries just 4 pins: VBUS (+5V power), a D+/D- differential data pair, and GND -- the simplest USB pinout, with no reversibility and no Power Delivery negotiation lines. DB9/RS-232 has 9 pins, but a basic connection only needs 3: pin 2 = RXD (receive), pin 3 = TXD (transmit), pin 5 = GND. The remaining pins carry modem-control signaling most simple serial links don't use.

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End A

USB Type-A

01 VBUS +5V power. Slightly longer than the other pins so it mates first and breaks last.
02 D+ / D− The differential data pair -- the same signal inverted on each wire, so noise cancels at the receiver.
03 GND The common ground -- the voltage reference every other signal is measured against.
04 Metal shell The plastic tongue sits in one half of the shell only, which is why the plug goes in one way up.
05 Strain-relief boot Stops the wires flexing where they leave the plug — the exact point most cables fail.
06 Outer jacket The outer sheath protecting the conductors inside from abrasion and moisture.

Technical illustration, not a photo of the actual product

End B

DB9 (RS-232)

01 9 pins A 9-pin serial port, but a basic connection only needs 3: pin 2 = RXD (receive), pin 3 = TXD (transmit), pin 5 = GND. The remaining pins carry modem-control handshaking most simple serial links don't use.
02 D-shaped shell The D profile only fits one way round, so the plug cannot be inserted upside-down and bend its pins.
03 Thumbscrews Hand-tightened to hold the plug home. A loose one is why a picture flickers, or loses one colour channel.
04 Strain-relief boot Stops the wires flexing where they leave the plug — the exact point most cables fail.
05 Outer jacket The outer sheath protecting the conductors inside from abrasion and moisture.

Technical illustration, not a photo of the actual product

From the published standard

How it works

An internal chip (often an FTDI family part) translates between digital USB signalling and RS232's traditional voltage levels (±5 to ±15V), appearing to the system as a virtual COM port through a driver. Legacy equipment -- PLCs, point-of-sale printers, industrial gear -- expects exactly that voltage and protocol, not USB directly.

Function: USB-to-RS232 level translation, appears as a virtual COM port
Common chipset: FTDI-family USB-serial bridge

This information comes from published sources about this type of product, not from the supplier.

en.wikipedia.org

Applications

Connecting a modern device to an older screen
Driving a meeting-room projector

Technical specifications

Type	Converter
Connectors	USB-A / DB9

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