Epson Projector RS232 Not Working? A Step-by-Step Fault Check

The fastest way to find an Epson RS-232 fault is to classify the reply, not to swap cables at random. ESC/VP21 gives you three distinct outcomes: a bare colon, ERR followed by a colon, or nothing at all. Each one points to a different layer. Send a lone carriage return first. If a colon comes back, the cable, the COM port and the serial settings are proven, and the fault is in the command, the timing or the projector's state. If nothing comes back, you are looking either at a wiring, port or menu problem, or at a projector in an abnormal state — and Epson's own guide says a projector in an abnormal state neither executes commands nor returns a colon, which is exactly why the two get confused on site.

This page walks the checks in that order. The general command list, the pinout table and the PWR? status values are in the Epson ESC/VP21 command guide; here the focus is on what each symptom means and which documented Epson rule explains it.

Before You Start: Use a Tool That Shows the Reply

Every check below depends on seeing what the projector sends back. Epson's ESC/VP21 guide describes the protocol as ASCII command codes that can be driven from a PC running a terminal emulator, so a terminal program on the same COM port is the right diagnostic tool.

Set the terminal to the communication conditions in the ESC/VP21 appendix: 9600 bps, 8 data bits, no parity, 1 stop bit, no flow control. The user's guide for the newer EB-L690/L695/L790/L890/L895 series words the rate as a "Default baud rate setting" of 9600 bps. None of the Epson documents this page is based on list any other selectable baud rate or the menu where one would be changed, so start at 9600.

In SoftControl, the serial driver opens the port at 8 data bits, 1 stop bit and no parity, writes the bytes, waits 50 ms and does not read a reply. That is fine for production control but useless for diagnosis: it cannot show you a colon or an ERR. Do the tests on this page in a terminal emulator, then move the strings that work into SoftControl.

Step 1: Send the Null Command and Look for a Colon

The null command is the return key code on its own. Epson defines it as the way to confirm that the projector is in operation, and the reply is a colon.

Send:    <CR>        hex 0D
Expect:  :           hex 3A

Verification: from-vendor-doc — per Epson's ESC/VP21 Command User's Guide; not tested against real hardware in this repo.

Colon back: skip to Step 2. Nothing back: work through 1a to 1e in order, and do not start testing real commands until the colon appears.

1a. Cable type

Epson specifies a crossover (null modem) cable. In the wiring diagram of the EB-L690/L695/L790/L890/L895 series guide, GND pin 5 goes to pin 5, the projector's TD (pin 3) goes to the computer's RD (pin 2), and the projector's RD (pin 2) goes to the computer's TD (pin 3). A cable that does not cross pins 2 and 3 does not match that diagram. The full wiring walk-through is in the Epson RS232 pinout guide.

1b. Connector shape

Not every Epson uses a full-size D-Sub 9. The EB-PU2220B/EB-PU2120W manual lists the RS-232C port as a Mini D-Sub 9-pin (male), so those projectors need a matching adapter cable. The pin assignment of that mini connector is not given in Epson's official materials reviewed for this page; check the manual for your exact model.

1c. The COM port, especially over USB

Some older models accept ESC/VP21 over USB. This needs the EPSON USB COM Driver on the computer; once the projector is connected by USB, a new port appears in Device Manager as EPSON COM Emulation port (COMn), and that COMn is the port to open. The appendix names two installers: EMPUSBSetup.exe for the 600/800/810/811/820, 720/730/520, 73/53/74/54 and 735, and EMPUSB2Setup.exe for a longer list of later models, starting with the 7800/7850, 8300/9300, 61/81, 830/835 and 740/745.

1d. Is the port enabled in the menu?

For the serial models it covers, the ESC/VP21 appendix says: "Select RS-232C at Advanced Setting of the Menu." USB control has its own per-model setting: USB under the advanced setting (600/800/810/811/820, 74/54), Link 21L under Advanced Setting (720/730/520, 73/53, 740/745, 732/737, S3/S4/X3, 760/765, 1715/1710/1705/1700, S5/X5, 260), USB under Advanced2 (8300/8350/9300), USB under Extended (61/81, 830/835/821), or Wireless Mouse plus Link 21L under Extended (1735W/1730W/1725/1720, S6/X6/W6 through S10/X10/W10, 1760W/1770W/1775W/750).

Note that in Epson's appendix, Link 21L is a USB option, not the serial one. For current models, the menu path that enables serial control is not stated in Epson's official materials reviewed here; use your model's manual.

1e. HDBaseT has taken the port

On the EB-PU2220B, Extended > HDBaseT > Control Communications enables the Ethernet and serial ports on the HDBaseT transmitter or switcher; the manual says to "set to On to disable the projector's LAN, RS-232C, and Remote ports." With that setting on, a cable plugged into the projector's own RS-232C port gets no colon however well it is wired. Either turn the setting off or wire control to the transmitter side.

If 1a to 1e all check out and there is still no colon, go to Step 4: an abnormal state produces the same silence.

Step 2: The Colon Works, but the Command Returns ERR

An invalid command gets ERR, a return code and a colon:

Reply to an invalid command:
ERR<CR>:      hex 45 52 52 0D 3A

Verification: from-vendor-doc — per Epson's ESC/VP21 Command User's Guide; not tested against real hardware in this repo.

Receiving ERR is itself proof that the link works: the reply travelled back over the same cable. Stop checking wiring. Epson gives two reasons that apply to all projectors — the command format is not good, or the projector is not ready to reply — plus a third that depends on state.

Standby accepts only a short list

In standby (operation indicator orange), which commands execute depends on the model and on whether the standby configuration is network on or network off. In the power-on state (indicator green), all commands are executable. The guide's notes name three model groups explicitly:

Verification: from-vendor-doc — per Epson's ESC/VP21 Command User's Guide (Rev.Q, section 4.1 notes); not tested against real hardware in this repo.

So SOURCE? returning ERR on an EMP-830 in standby is documented behaviour, not a fault. PWR ON, PWR? and the null command are the three that appear in all three of those groups, so on those models they are the commands to probe with when you do not yet know the projector's state. For other models, check the standby table in the guide for your model.

Timing rules you may be breaking

• Power-on state: send a command only after receiving the colon of the previous one.

• Standby with "network on": the first command can be sent at any time; later ones only after a colon.

• Any other standby: only PWR ON can be sent at any time.

• Exception: after PWR OFF to a 7800/7850/8300/9300 with "network off", send the next command 10 seconds after the colon arrives.

The guide does not describe what happens when these rules are broken, other than that a projector not ready to reply returns ERR.

Two notes attach to PWR OFF in the guide's execution-time table: projectors execute PWR OFF only after they have started completely, and for the 830/835 the projector might return ERR when the "Quick Setup" and "Auto Focus" functions are set to ON.

Step 3: The Colon Is Slow, or the Picture Does Not Change

• Lamp ignition. On PWR ON the projector tries to ignite the lamp up to three times. It returns the colon within 40, 70 or 100 seconds if the first, second or third attempt succeeds. Three failed attempts are a lamp failure. A missing colon at 45 seconds is therefore not yet evidence of anything.

• Unstable sync. A note in the execution-time table says the colon is returned within 5 seconds when the input video sync signal is stable, but may take more than 5 seconds when it is unstable.

• SOURCE during signal changes. On a SOURCE command the projector starts recognising the input signal. If the signal changes during that process — Epson's example is an A/V controller switching the source from SVGA to XGA — the projector returns ERR. Let the source device settle before switching inputs.

• Warning lights. While a warning indicator such as a high-temperature warning is on, the projector still executes commands normally. A warning LED alone does not explain a control failure.

• No colon handling at all. If your controller cannot wait for colons, Epson's alternative is to space commands by the execution times in its table. The values run from 3 to 130 seconds depending on command and model, so read the row for your model rather than applying one number to every projector.

Step 4: No Colon on a Link That Used to Work

Epson's guide is explicit: in an abnormal state such as a lamp failure or abnormal high temperature, the projector does not execute commands and does not return a colon. At the serial level this looks identical to a pulled cable.

For the EMP-6100/6000, EMP-1715/1710/1705/1700, EMP-1815/1810, EMP-S5/X5/83/822 and the models that follow them in the guide, PWR ON becomes possible again only after the abnormal state has continued for 130 seconds. Retrying sooner is wasted effort on those models. On models that report it, PWR? returning 05 means abnormal standby.

Once the projector answers again, send ERR?. The guide lists a group of models (EMP-1700/1705/1710/1715, 6000/6100/6110/6010, 1815/1810/1825, S5/X5/83, EB-G5000/G5100/G5150/G5200W/G5300/G5350 and later models) that can return the error status after cooling down. The return codes:

Verification: from-vendor-doc — per Epson's ESC/VP21 Command User's Guide (Rev.Q, section 6); not tested against real hardware in this repo. Which codes a given model can actually report is model-dependent.

Step 5: Going Over the Network Instead

ESC/VP21 itself is transport-independent, but on a network the guide says commands can be sent once a TCP session is established, and defers to the ESC/VP.net manual. Epson's FAQ has you connect to TCP port 3629 and send a 16-byte handshake before any command; the projector answers ESC/VP.net. The handshake and its replies are covered in Epson projector network control.

If ESC/VP.net monitoring and control fails, the EB-PU2220B manual's fix is to set Network > Network Configuration > Others > Command Communication to Compatible. Protected allows only version 2.0 with the Web Control Password (digest authentication); Compatible accepts version 2.0 or 1.0, with version 1.0 using the Monitor Password (plain text, up to 16 alphanumeric characters). The manual says to select Compatible when monitoring projectors with a switcher and a system controller, and Epson's online guide adds that one of the two passwords must be set before ESC/VP.net commands are usable.

For network control while the projector is in standby, the same manual requires Extended > Standby Mode set to Communication On — which in turn needs A/V Output set to While Projecting, Auto Power On set to Off or Computer, and USB Power set to On While Projecting.

Field Notes: Where the Hours Go

• Two causes of silence. A wiring fault gets no reply at all, and a projector in an abnormal state returns no colon. On a link that worked yesterday, check the indicators and wait out the 130-second window on the listed models before re-terminating anything.

• ERR mistaken for a bad cable. An ERR reply proves the wiring. The guide gives three reasons for it: the command format is wrong, the projector is not ready to reply, or the projector is in standby and the command is outside that model's standby list.

• Controllers that never wait for the colon. SoftControl's serial driver is one of them: it sends and moves on. Command spacing therefore has to come from delayMs, sized from Epson's timings.

• HDBaseT Control Communications left on. With Control Communications on, the projector's own RS-232C port is disabled.

• Link 21L chased as a serial setting. In Epson's appendix it belongs to USB communication.

A compact order of checks for the job sheet:

1. Null command (0D) -> colon?          no  -> cable / connector / COM port / menu / HDBaseT
2. Command -> ERR<CR>: ?               yes -> format, not ready, standby list, timing
3. Colon slow / no visible change?     -> lamp retries (40/70/100 s), sync, SOURCE during change
4. Silence on a known-good link?       -> abnormal state; wait 130 s (listed models); ERR?
5. Network?                            -> ESC/VP.net handshake on 3629; Command Communication = Compatible

SoftControl Import Snippets

SoftControl does not add a carriage return on serial, so it must be written into commandText as \r (text format) or 0D (hex format). Power on, text and hex forms are equivalent:

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

name: Projector power on (hex)
protocol: serial
targetIpOrCom: COM1
portOrBaud: 9600
payloadFormat: hex
commandText: 50 57 52 20 4F 4E 0D

Because SoftControl does not wait for the colon, put the gap on the second command. delayMs is the wait before that command runs. The value below is the longest colon time Epson documents for a successful PWR ON (third ignition attempt, 100 seconds) in the lamp models its guide covers; for other models, check that model's Specifications and the execution-time table in the ESC/VP21 guide. Replace 30 with your model's input code — the same code means different inputs on different Epson models.

name: Projector input select
protocol: serial
targetIpOrCom: COM1
portOrBaud: 9600
payloadFormat: text
commandText: SOURCE 30\r
delayMs: 100000

Verification: from-vendor-doc — command strings and timings per Epson's ESC/VP21 Command User's Guide; not tested against real hardware in this repo.

For network control, SoftControl's TCP driver does not perform the ESC/VP.net handshake, so use its PJLink driver on port 4352 instead:

name: Projector power on (PJLink)
protocol: pjlink
targetIpOrCom: 192.168.1.50
portOrBaud: 4352
commandText: %1POWR 1

Verification: from-vendor-doc — PJLink command per the PJLink specification; not tested against an Epson projector in this repo.

Start every service call with the null command in a terminal. Whether a colon, an ERR or silence comes back decides which of the five steps you are in.