Help with C-series Ex-Link Serial

[timdenike]

Hi folks,

I'm guessing this is a routine question, but I'm looking for advice nonetheless. I've been trying to enable serial on my UN55C6500 LED display. I enabled "Diag" serial in the service menu. After a brief attempt going straight from RS232->Ex-Link, I discovered the need for a TTL converter. I wired up a new connector, but still no luck.

I'm using a MAX202 package, first with a +5 external supply, then next with a +3v battery supply, which seemed to drop the output voltage around where I wanted. In either setup, I still get no data passing through to the terminal side. Oddly, my MAX202 gets burning hot when connected to the TV, so I'm clearly missing something.

I've tried flipping the TX/RX both ways. I connected my oscilloscope up to the Ex-Link leads and can see one conductor pushing a data stream when I power it on-off. (Guessing some kind of startup console output.)

I've seen other threads that describe the need for a voltage regulator circuit between the TTL chip and the display panel - is this needed? Other sources say the TTL adapter should output 3.3v.

I've also got another TTL adapter based on the MAX3238E arriving tomorrow which seems to have more flexibility.

[timdenike]

Had slightly better luck with www.robotshop.com/droids-db9-serial-adapter-5.html based on a max3238E chip.

When I connect the tip of the Ex-Link/audio plug to the RX pin of the TTL converter (plus ground), I see log output on my terminal app. I get a good burst when I power on the display, then a bit more, then quiet. Sadly, it's all garbage data. If I connect the pins in any other configuration, I get nothing, so I assume I'm wired up right.

I've tried powering the TTL converter with both +5vdc and +3.2vdc, or even unpowered. (Input power is supposed to determine the output TTL voltage level.) No difference either way - all show what appears to be garbled data at boot/shutdown of the TV.

[juusso]

No experience with usa models, but some E series plasmas, which have rs 3,5 service socket doesnt need ttl converter. I mean direct rs232-service port of tv is used.
How about c series? Checking may be dangerous and if i`m wrong - you can burn your tv/pc...
Another doubt what came in to my mind is your usb2ttl adapter. Best experience we do have is with cables, based on pl2303 chip, then no external power is needed. I`m not familar with max232 chip based dongles, as well as with cp21xx, cant troubleshoot your problem.

[timdenike]

My first attempt was direct rs232, which actually yielded identical results: Garbage data at power on/off.

If this attempt had damaged the display, what would the symptoms be? Do damaged boards usually go dead, or could I have killed it in a way that it only pushes garbled data?

FWIW, I am using a PL2303, just using an external rs232-ttl converter. (My goal was to connect the converter to an ethernet-serial bridge.) Perhaps buying the cable you suggest might help me diagnose further.

Is my assumption that the tip of the Ex-Link cable is the display TX, correct? If I clip my voltmeter on this lead I see 0V base with spikes to +2.2v, presumably when data is on the line.

I do also have another Samsung HP-S4253 with a similar port, but haven't dug into what sort of display that is, yet.

[juusso]

Garbage on the terminal screen usually mean wrong connection settings. During TV boot you have to see a lot of garbage, not only at power on/off - this perhaps means you need ttl converter. And if you still see some garbage, i think your service port is still ok

Pinout of ExLink, connection settings you can see here: http://wiki.samygo.tv/index.php5/Ex-Lin ... connection

[sbav1]

If I clip my voltmeter on this lead I see 0V base with spikes to +2.2v, presumably when data is on the line.

It's a little weird; for 3.3V-level serial, on TX pin it should be around 3.0-3.3V base (while idle), and dropping to 0V while transmitting data. RX pin also usually measures +3V, due to pull-up resistor connected to 3.3V VCC (if any).

Anyway, if this 3.5mm port in your TV is labeled as "EX-LINK" (and not as "SERVICE"), you should generally expect regular RS232 levels (+/-12V) on such port.

I'm not familiar with UN models, but - on the UN*C6500 mainboards (eg.: http://www.shopjimmy.com/samsung-bn94-0 ... 0vfxza.htm) RS232 voltage level converter chip seems to be already included (looks like MAX3222, in the very bottom-right corner). In C6/7/8XXX EU models, there was a place for such chip on the mainboards as well - Samsung just "forgot" to solder the relevant parts in their EU offerings.

Btw, you sure your terminal & service menu settings are correct? I've never heard of 'Diag' setting for serial port in factory menu; for gaining access to serial console, RS232 port usually needs to be set to 'Debug'..

[timdenike]

Aha! That's incredibly helpful. Yay for Jimmy and his hi-res photos and hard-to-find parts.

My port does say "Ex-Link", and I did start this whole effort trying rs232 direct, with identical results - same garbled data. So perhaps you're right about this being rs232 and not TTL.

I'm relaying some of this from memory, but I recall there being 3 choices for UART, "debug" is more likely. That's the only setting I've changed. Enabling hotel mode changed nothing. If I turn off "debug", the garbled output at boot/shutdown goes away. Tried all possible bps settings, and confirmed my terminal works by connecting to another serial device.

I'll try again tonight with rs232-direct.

[juusso]

We`re talking about terminal connection settings, not service menu settings. And definitely in service menu you need rs232 - debug.

SpoilerShow

[timdenike]

.. And sure enough, it works just fine direct serial. I guess my serial-ethernet server is junk. I'll have to think of something creative to do with those TTL converters.

Any idea if this series display doesn't use the regular samsung serial commands? I've only been poking on this code for a few minutes, but don't seem to be able to get the console to respond to pretty much any input, yet.

Code: Select all

import serial

ser = serial.Serial('/dev/tty.usbserial', 115200, timeout=1)

toggle = "\x08\x22\x00\x00\x00\x00\xd6"
off    = "\x08\x22\x00\x00\x00\x01\xd5"
on     = "\x08\x22\x00\x00\x00\x02\xd4"

ser.write(bytes(off))
ser.flush()
ser.close()

[sbav1]

Any idea if this series display doesn't use the regular samsung serial commands?

Oh, you mean: to remotely control TV via Ex-Link port? For that, you need set RS232 port in service menu to "UART" (not "Debug"; debug is for SoC serial linux console - I just assumed this was what you wanted), and perhaps use different serial settings as well (9600, not 115200??? - not sure about that, I've never used this feature in any C/D/E-series models personally).

Generally, I expect Ex-Link command to work with your TV model. One possible exception: "Power On" (i.e. turning TV on from standby state) is known not to work as expected in many B/C-series models (such was the case for my B650 - in this particular case, it doesn't work, because serial port multiplexer chip on the mainboard isn't properly powered from standby +5V power). Samsung designer apparently omitted this little detail - by mistake, or perhaps they just don't care all that much..