RS232: is DSR missing on my FT232 chip? and do I really neeed it?

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Hello,

 I need to connect my old projector Epson EMP TW-700 to my laptop to figure out if there is an error message why it does not show images. I thought RS232 would do the job because it is possible to power on the projector via RS232 and it returns some diagnostic info during the process.

 

I need to connect the projector via RS232, the wiring is like this image

EMP TW700 serial port wiring

I wanted to connect it to RS232-to-USB that I had at home, that is a FTDI232 like this one in the image

FTDI232 chip

The chip itself seems to have a DSR pin, but I do not find a pinhole or pin for it. Does it mean I cannot use this RS232-to-USB for my purpose? or maybe the DSR is not necessary? or it is just renamed to something else on the circuitboard for some funny reason?

 

Please help on how to connect the projector to this RS232-to-USB because as of now I do not get anything on the terminal when I power on the projector and I suspect this missing pin may be the reason.

Thanks

Roberto

 

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RSD?

 

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It is extremely unlikely you need anything besides rx & tx.   Ensure rx is connected to tx & that tx is connected to rx

Make sure both units have a gnd wire between them...so 3 wires total.

 

First, test your terminal set up...no projector.  Hook your board rx to its tx & see if you get an echo back of everything you type (send out) from your laptop terminal straight back to the laptop.

 

The projector & laptop bauds, parity, etc need to match

 

Why didn't you just get an adapter cable, no pcb needed?

 

see page 9 for your settings...9600 baud   ...I found this remote commands manual for your projector

https://files.support.epson.com/pdf/pltw1_/pltw1_cm.pdf

 

Is the bulb even working?  They can cost a few $$$

 

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Sat. Jan 25, 2020 - 10:18 AM
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Thanks, Indeed on the 28-pins package the documentations shows the DSR with its proper name and then I could follow the track to a pinhole on the board. It is (at least for me) weirdly (re)named RSD, left-right reversed, but it seems to be right pin. Now I have to address why the projector seems mute ...

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Thanks a lot for these suggestions. Indeed a cable may have been handy, but I do not have it here and I had the board, which also seems to be able to do the job, in principle.

 

Great tip, I did check the RS232-to-USB can talk to itself

~>echo -ne 'foo' > /dev/cu.usbserial-00000000

~>cat -v < /dev/cu.usbserial-00000000
foo

I can also see in cu what I type from programs like SerialTools (Mac) but I do not get in cu or screen anything I send via echo -ne 'foo' > /dev/cu.usbserial-00000000, at least until I connect and send something via SerialTools, then it works. This may be a key to the story, as cu seems to display something only after some "opening  signal" is received. Any suggestion on that?

 

To give the full background, as you also seem to be interested in the repair history/details, let me say that I have started this repair buying a new bulb, and when that did not solve the issue I was really puzzled. So I have opened the projector and checked a few things that are said to be weak points. The two thermistors read 10KOhm so they should be fine, AFAIK, but I did find one fan that was not running when put under tension. The exact replacement part is no longer sold, but I found one from the same maker that is said to be its replacement. Now that I have put the fan in place I am very puzzled as of why the projector does not start anyways ...

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Note - your board is not rs232 to usb! It is serial to usb. For rs232, you need an rs232 interface chip.

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I have done some more research and indeed the description of this board was "USB-to-TTL". In the docs of the chip it is described how to use it for USB-to-RS232, but it also says "a TTL to RS232 Level Converter IC is used on the serial UART interface of the FT232R to convert the TTL levels of the FT232R to RS232 levels" , so I think you spotted it. This board is not good.

 

I am exploring if I can use my raspberry pi instead of the cable (cannot buy it here at the moment, not in store), but I need to check the voltages to see if are ok for the Pi (it is designed for 3.3V).

My projector seems to give 5.5V (measured voltage difference between GND and TD pins in DC with multimeter). Do you reckon this is a valid measurement of the output voltage of this projector RS232? (that would make out of question to use the Pi as the signals seem too high voltage)

 

I am going to look for a cable as a failsafe, any special feature of the cable or USB-to-RS232 should be just fine? (RS-232C-to-USB seems to be unknown on the market)

Thanks for the advice,

Roberto

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Note: once you have the correct USB to RS232 adapter, you will need a NULL modem cable to connect your adapter to your projector.

Depending on which type of connector is on the adapter (either a 25 pin connector, or a 9 pin connector) both are common RS232 connectors, the NULL modem cable will need to be selected to fit both ends.

One other glitch you may run into is the device may be either male pin or female pins, while the cable end may be the same, if so, you will also need a gender changer adapter too.

RS232 works well, but getting the right cable with the right ends was always fun! I always had a load of adapters with me when working on these connections.

Come back if you still have problems, and we can help to get your comms working.

Jim

 

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You can use a max232 chip to convert your board to true rs232 voltage levels

 

for the rpi you can get a board

https://www.robotshop.com/en/rs232-serial-pi-plus-converter-raspberry-pi.html

 

Most or all of these cables will give you a true rs-232 voltage (double check the specs) ...they can ship it right to where you live.

https://www.walmart.com/c/kp/usb-to-serial-adapter

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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Thanks for the tips, indeed I had overlooked the issue of M/F connector and that the cable has to be done so that RX talks to TX. In view of this, am I fool to use a USB-to-RS232 board like this one ?

It seems to have the obvious advantage that the pins are exposed and I can easily make sure RX is connected to TX and not to RX. In fact the description of the cables is rather scarce as of what kind of pin layout they have.

Of course, if needed, I can use Dupont sockets to connect the male port to the right pins of any cable I get (male or female), once I have figured the pin layout of the cable. Am I missing some obvious advantage of the cable?

 

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In the days of DB9 and DB21 connectors, devices were always connected by cable. You RARELY had two devices (e.g. circuit boards) plugging into each other directly using that connector style. So, don't expect you USB-RS232 adaptor, what ever it is,  to plug directly into the projector. Get an appropriate pair of connectors and make your own cable. Then, you can also connect RTS to DTS, as was commonly but not always done. 

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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It is extremely unlikely you need anything besides rx & tx. 

 

 

I would have thought the opposite.

 

If the projector didn't use any handshake signals then they would not have taken the time to include them in the hardware and in the diagram.

Back in the day it was common to use the handshake signals with modems, cash registers, weigh scales, etc.

They were also commonly used with printers that used a serial interface instead of the Centronics parallel interface, and with "dumb" terminals.

 

I'd suggest Foice read the Wiki RS-232 article for some background info.

 

Bottom line, RS-232 is a bi-polar signal, often +/- 12 V, but can be +/- 3V to +/- 25 V.

In the old days many devices didn't want to spend the money to generate a negative voltage on the PCB so they used +5 or + 12 V and Ground, (Ground replacing the negative voltage level).

That was technically out of spec, but was commonly used, and depending upon the hardware chip for the RS-232 interface it usually worked fine.

There were also some cheap transistor RS-232 interfaces that, depending upon the design, didn't work well without a true negative voltage of several volts.

 

Once you get the USB to RS-232 set up, you can likely just connect the TxData, RxData, and Ground pins from your setup to the projector, AND ALSO short the DTR pin on the projector to the DSR pin on the projector.

Without asserting the (likely expected) handshake signal you might well not get anything transmitted from the projector.

 

JC 

 

Edit: Typo

 

Last Edited: Sat. Jan 25, 2020 - 08:38 PM
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I looked at the manual for the projector...as I surmised, they only require 3 wires.

https://files.support.epson.com/pdf/pltw1_/pltw1_cm.pdf

 

Of  course, it can't hurt to include 2 more wires in your hookup.   If you just buy a usb adapter cable, everything is ready to go, nothing else should be needed.  We used those cables all the time to hook STK500's  & some old voltmeters to the PC usb

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Sat. Jan 25, 2020 - 08:48 PM
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Cable + female-female null modem has worked out. I was able to turn on the project from its stand-by state giving a command in the terminal. I also got the error messages I wanted, but they look awfully bad. I need to investigate more what they are trying to communicate, because it cannot be all "ERR".

Thanks for all the tips

Roberto

.response of SNO?: ERR
response of PWR ON:
response of LAMP?: LAMP=473
response of LUMINANCE?: ERR
response of BRIGHT?: ERR
response of CONTRAST?: ERR
response of TINT?: ERR
response of HREVERSE?: HREVERSE=OFF
response of VREVERSE?: VREVERSE=OFF
response of MSEL?: MSEL=01
response of ASPECT?: ERR
response of PWR?: ERR
response of SOURCE?: ERR

 

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Just a WAG, looks like a corrupted parameter storage EEPROM, look to see if you can init the parameters to factory settings.

Jim

 

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If you ever get the unit working, this might be of interest:

https://github.com/feg-giessen/ProjectorCtrl

 

I'm not 100% sure, upon a quick perusal, "err" as a response shows it is an invalid command (not all models understand all commands) or if there is some error state, some commands are temporarily not available. 

The manual link I sent does not show those commands---either they don't exist for TW700 model, or that manual is not for service people, so they simply aren't listed.....

 

did you try the ERR? command...hopefully it is #7

 

 

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Mon. Jan 27, 2020 - 10:09 PM
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I realize that my projector is listed under

Home Projectors

so it does not enjoy the utility of `ERR?` ... this means it's giving out not diagnostic info as far as I can tell. That's a bummer ...

And yes, you are correct that these many `ERR` responses just mean that the command is unknown. So I am making no progress here as of why the projector does not start, I am still stuck with the (slowly) flashing light/temp LED which on the manual give a very generic error list

Internal problem / Fan problem / Sensor problem / Cinema filter problem / Auto iris problem

 

At this point I am clueless on what the problem could be. I may try to check if the fans are not just spinning but also sending out their signal to the projector (these fans have a "blocked fan signal") and retest the thermal sensor, as this video claims they can be "flaky" too.

 

Flashing

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When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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I am familiar with this assembly scheme and the part list (from a german part vendor as far as I know). What use of it are you suggesting?

 

At the moment I am trying to put an oscilloscope on each fan, even though are spinning, to check the "Rotor Lock" signal is ok, according to the fan manufacturer "specs". Please note the original fan was NMB 3110KL-04W-B49 and I have put 3110KL-04W-B59, because the B49 is not available anywhere. it should just be a bit faster spinning (4-->5).

 

Last Edited: Tue. Jan 28, 2020 - 09:03 AM