Epson Projector RS232 Pinout: DB9 Wiring and Null Modem Cable

An Epson projector talks ESC/VP21 over three conductors: ground on pin 5 to pin 5, the projector's transmit (pin 3) into the computer's receive (pin 2), and the projector's receive (pin 2) fed from the computer's transmit (pin 3). Epson specifies a crossover (null modem) cable for this. Before you write a single command, prove the wire by sending a lone carriage return and waiting for a colon. If nothing comes back, the cable is only one of several suspects: some models have a Mini D-Sub 9 port instead of a full-size one, some are meant to be driven over USB through a virtual COM port, and on HDBaseT installs the projector's own RS-232C port can be switched off by a menu setting.

This page covers the physical side in more depth than our Epson ESC/VP21 command reference: which connector you will actually find, what each wire does, the USB alternative, and the order to check things in when the link stays silent.

Which connector is on your projector

Epson does not use one connector across the range, so check the rear panel against the manual for your exact model before you order or build a cable.

D-Sub 9-pin, male, labelled RS-232C. This is what Epson's cable-layout page shows for the EB-L690/L695/L790/L890/L895 series. The same page names the cable type as a crossover (null modem) cable.

D-Sub 9-pin, labelled Control(RS-232C). The older ESC/VP21 command guide (Rev.Q) gives "D-Sub 9pin" as the connector and "Control(RS-232C)" as the projector input for the long list of serial-capable models in its appendix, from the 600/800/810/811/820 generation through to models such as the 1830/1900/1910/1915/1920W/1925W, G5350/G5300/G5200W/G5150/G5100/G5000 and the Z-series models listed there.

Mini D-Sub 9-pin, male. The EB-PU2220B / EB-PU2120W user's guide lists the RS-232C port as a Mini D-Sub 9-pin male connector, used "to connect an RS-232C cable to control the projector from a computer".

For the Mini D-Sub 9 port, the pin assignment is not given in the Epson pages we work from; Epson's official documentation available to us does not describe it. Do not assume it follows the full-size layout below. The same manual's interface page tells you to check the shape and orientation of each connector, not to force a plug that does not fit, and to use an adapter where one is needed to reach the projector's port.

The computer side of Epson's diagram is also a D-Sub 9, but Epson's page does not state its gender. The only gender Epson commits to is the projector's: male.

Pin by pin: Epson's crossover diagram

Epson's diagram puts the projector on the left and the computer on the right. Three signals are defined, each with a one-line function:

Projector pin	Projector signal	Epson's description	Computer pin	Computer signal
5	GND	Signal wire ground	5	GND
3	TD	Transmit data	2	RD
2	RD	Receive data	3	TD

Read the table as three separate jobs.

Pin 5 to pin 5, ground. Epson describes it as the signal wire ground. It is the only straight connection in the diagram: pin 5 on one end goes to pin 5 on the other.

Projector pin 3 to computer pin 2. Pin 3 on the projector is TD, the pin the projector talks on. Every reply you will ever see, including the colon prompt and the ERR response, leaves the projector on this pin. It has to arrive on the computer's RD, which is pin 2 on the computer side of the drawing.

Projector pin 2 from computer pin 3. Pin 2 on the projector is RD, where it listens. Your commands leave the computer on its TD (pin 3) and must land here.

That is the whole reason the cable must cross. Both ends in Epson's drawing use the same numbering: pin 2 is receive and pin 3 is transmit on each side. A straight-through cable connects pin 3 to pin 3 and pin 2 to pin 2, which puts transmit against transmit and receive against receive. The projector never hears the command, and the computer is not listening on the pin the projector talks on. The practical signature is total silence: no colon, and no ERR either, because ERR is also a reply that needs the projector-to-computer path. If you need a refresher on telling the two cable types apart with a meter, see RS232 null modem vs straight-through.

Epson's current diagram draws only these three conductors. This article does not cover any other pin; if the manual for your model draws a different layout, follow the manual.

Line settings that go with the cable

The wire only works if both ends agree on framing. Epson's appendix lists 9600 bps, 8 data bits, no parity, 1 stop bit and no flow control. The newer cable-layout page words the speed as "Default baud rate setting: 9600 bps" and gives the same 8 / None / 1 / None for the rest. It does not list any alternative speeds, so this article does not either. The menu side of serial setup is covered in Epson projector RS232 baud rate and settings.

Prove the wire with one byte: the null command

ESC/VP21 has a built-in line test. Epson calls it the null command: the return key code on its own, hex 0D. The projector answers with a colon, and the guide says the null command "can be used to confirm that the projector is in operation". Any terminal emulator works; Epson's own guide mentions controlling projectors from a PC with a terminal program such as HyperTerminal.

computer -> projector:  0D               (null command: CR only)
projector -> computer:  3A               (":")

What the reply tells you about the cable:

A colon comes back. Both data paths and the ground work, the COM port and line settings are right, and the projector's serial input is active. Move on to real commands.

ERR comes back. Epson documents the illegal-command reply as ERR, then a carriage return, then a colon. Getting those bytes proves the wiring just as well as a colon does, because they travelled projector TD to computer RD. The problem is the command text or the projector's state: Epson says all projectors return ERR when the command format is wrong or when the projector is not ready to reply.

projector -> computer:  45 52 52 0D 3A   ("ERR", CR, ":")

Nothing comes back. This is the case the rest of this page is about. Silence can be the cable, but Epson also documents that a projector in an abnormal state, such as a lamp failure or abnormally high temperature, neither executes commands nor returns a colon. A silent line is therefore not proof of bad wiring.

Standby is not automatically a reason for silence. For EMP-61/81/830/835/740/745/821/828, Epson lists the null command among the few commands accepted in standby, together with PWR ON, PWR? and LAMP?. EMP-7800/7850 and EMP-8300/9300 also include the null command in their standby lists. For other models, check the standby table in the ESC/VP21 guide for your model.

Verification: from-vendor-doc — the null command, colon and ERR bytes are per Epson's ESC/VP21 command guide; not tested against real hardware in this repo.

USB instead of DB9: Epson's virtual COM port

The ESC/VP21 guide lists models that accept the same commands over USB. The computer needs the EPSON USB COM Driver. Once the projector and computer are connected by a USB cable, a COM port is added, and it is listed under PORT (COM/LPT) in Device Manager as EPSON COM Emulation port (COMn). That COM number is what your control software has to open.

The guide names two driver installers, split by model:

EMPUSBSetup.exe for 600/800/810/811/820/720/730/520/73/53/74/54/735.

EMPUSB2Setup.exe for a longer list that includes 7800/7850/8300/9300, 61/81, 830/835, 740/745, S3/S4, S5/X5, S6/X6/W6, S7/X7/W7, S8/X8/W8, S9/X9, W10/S10, 1715/1710/1705/1700, 1760W/1770W/1775W/1750, W01/S02/X02/W02/S11/X11/S12/X12/W12/X14 and others in the guide's table.

The projector also has to be told to listen on USB, and the menu item differs by model:

600/800/810/811/820, 74/54: select USB in the advanced setting of the menu.

720/730/520, 73/53, 740/745, 732/737, S3/S4/X3, 760/765, 1715/1710/1705/1700, S5/X5, 260: select Link 21L in Advanced Setting.

8300/8350/9300: select USB in the Advanced2 setting.

61/81, 830/835/821: select USB in the Extended setting.

1735W/1730W/1725/1720, S6/X6/W6, S7/X7/W7, S8/X8/W8, S9/X9/W9, S10/X10/W10, 1760W/EB-1770W/1775W/750: select Wireless Mouse and Link 21L in the Extended setting.

Note that in Epson's guide, Link 21L is a USB option. It does not enable the DB9 port. For DB9 on the older serial models, the guide's instruction is to select RS-232C in Advanced Setting.

Two gaps to be aware of. The guide lists line settings under the serial connection heading only; it does not give separate settings for the emulated USB port. And the USB tables stop at the models in that guide. For newer models, Epson's official documentation available to us does not describe USB control, so check your model's manual.

HDBaseT: when the local RS-232C port is switched off on purpose

On the EB-PU2220B / EB-PU2120W, the Extended menu has HDBaseT > Control Communications. Setting it to On enables the Ethernet and serial ports on the connected HDBaseT transmitter or switcher, and the manual states that it disables the projector's own LAN, RS-232C and Remote ports.

On site this looks exactly like a wiring fault: a correct crossover cable on the projector's RS-232C port gets no colon back. If the projector is fed from an HDBaseT transmitter, either send your serial commands through the transmitter's serial port, or set Control Communications back to Off before testing the local port. Other models may differ; check the manual for yours.

Field checklist: the order to work through a silent link

Work from the cheapest check to the most disruptive:

Connector. Full-size D-Sub 9 or Mini D-Sub 9? A Mini port needs an adapter, and its pinout is not in Epson's pages we reference.

Cable type. Epson specifies crossover. A straight-through cable gives no colon and no ERR.

COM port. For USB, open the port Device Manager names as EPSON COM Emulation port, and install the driver file that matches the model.

Line settings. 9600, 8 data bits, no parity, 1 stop bit, no flow control.

Projector menu. RS-232C selected for the serial port on the older models listed in the guide; USB or Link 21L for USB, per the model list above.

HDBaseT. Control Communications set to On disables the local RS-232C port on the EB-PU2220B / EB-PU2120W.

Projector state. An abnormal state gives no colon at all. On EMP-6100/6000, 1715/1710/1705/1700, 1815/1810, S5/X5/83/822 and later models, Epson says PWR ON becomes possible once the abnormal state has continued for 130 seconds.

Once the null command returns a colon, command-level faults are covered in Epson projector RS232 not working.

SoftControl import snippet

In SoftControl, an Epson serial command is a serial protocol entry. targetIpOrCom is the COM port name, portOrBaud is the baud rate, and SoftControl's serial driver always uses 8 data bits, 1 stop bit and no parity, and the code does not configure flow control. It does not add a carriage return for you, so the CR goes in commandText as \r (with payloadFormat: text) or as 0D (with payloadFormat: hex).

Power on over a DB9 crossover cable, text form:

name: Epson power on
protocol: serial
targetIpOrCom: COM1
portOrBaud: 9600
payloadFormat: text
commandText: PWR ON\r

The same command in hex, and power off, over the USB virtual COM port. Replace COM4 with the number Device Manager shows after "EPSON COM Emulation port":

name: Epson power on (USB)
protocol: serial
targetIpOrCom: COM4
portOrBaud: 9600
payloadFormat: hex
commandText: 50 57 52 20 4F 4E 0D

name: Epson power off (USB)
protocol: serial
targetIpOrCom: COM4
portOrBaud: 9600
payloadFormat: hex
commandText: 50 57 52 20 4F 46 46 0D

The USB entries use 9600 because that is the serial value Epson documents; Epson's guide does not give a separate figure for the emulated port.

One limitation matters for cable testing. SoftControl's serial driver writes the bytes and does not read a reply, so it will not show you the colon. Run the null-command test from a terminal emulator first, then paste the working command into SoftControl. For the same reason SoftControl does not wait for the colon between commands; when you chain several, put the gap on the later command's delayMs, using the execution time Epson lists for your model.

Verification: from-vendor-doc — command strings and bytes per Epson's ESC/VP21 command guide; field names per SoftControl's command model. Not tested against a real Epson projector in this repo.

Where to go next

With the colon coming back, the physical layer is done and every further problem is about command text, projector state or menu configuration. Keep the terminal session open while you add commands one at a time from the ESC/VP21 command list linked at the top of this page, and confirm each one returns a colon before you copy it into your control project.