OT - PL2303 with different Vendor ID

inglewoodpete

Senior Member
Not strictly a PICAXE question but I think there is a wealth of PL2303 knowledge amongst the forum's members.

I recently bought an LG Smart TV. The documentation indicated that it could be controlled externally from a suitably configured receiver via a "PL2303 chip-based USB to serial converter".

Having several Prolific PL2303 cables that I use for my PICAXE work, I plugged one into a USB port on the LG TV. The TV responded with a message (something like) "Unrecognised USB device inserted". Hmm: when is a PL2303 not a PL2303?

Digging deeper into the LG's owner's manual (they're getting better) revealed the following: "LGTV supports PL2303 chip-based (Vendor ID: 0x0557, Product ID: 0x2008) USB to serial converter which is not made nor provided by LG.". A quick check of my PL2303 cable, when plugged into my laptop, reveals Vendor ID: 0x67b, Product ID: 0x2303 Prolific Technology, Inc.

Being a TV, you can't just download an alternate driver to use a different USB device: you're stuck with the TV's firmware.

All sorts of questions come to mind. Ultimately, do members know how to identify one of the 'alternate' PL2303 (Vendor ID: 0x0557, Product ID: 0x2008) USB to serial converters? Alternatively, where I can buy one and be confident that I am buying a compatible converter. Ie in the packaging, without opening it? I don't want to buy 20 of them just to find one that works with the TV.
 

Goeytex

Senior Member
The PL2303 has a one time programmable rom (OTPROM) that contains the vendor ID. Unless you can get a blank 2303 and somehow get the special EEPROM writer program from Prolific, it seems you will have to find a 3rd party supplier that sells a PL2303 adapter specifically for your LG.

Addendum to above: From the PL2303 Datasheet:
The OTPROM can be programmed twice using the Prolific PL2303 EEPROM Writer utility software which can be requested from Prolific or authorized distributors.
So if you can get an adapter with a real PL2303 chip and a copy of the software, you may be able to do it yourself.

EDIT: I got lucky and found it. That vendor ID is registered to ATEN International.

The product you need is a UC-232A Serial Port

Look here in the usb.ids file
 
Last edited:

inglewoodpete

Senior Member
Two replies, both from Texas! Thanks for doing the research Goeytex. That lead on ATEN International got me Googling again after work today (it's currently Tuesday evening local time).

I managed to download a copy of the EEPROM programmer but it doesn't seen to recognise the PL2303 chip when the USB is plugged in. I'm assuming that the EEPROM is accessed via the normal USB connection to the converter: instructions that make sense to me seem to be non-existent. The EEWriter program tells me that I have to write to the EEPROM before it will read it. I have no way of telling what PL2303 chip I have without breaking open the plastic housing. I think my best solution is to buy a cable.

I've found a few suppliers, one of them is local but wanting around A$40 (~US$37) for the converter. To me, that's a tad expensive but I don't want to gin around for weeks.

@Texasclodhopper - No, I haven't called LG's Australian support line. I'm put off by my experiences with other vendor's support lines - they seem to cater for the "consumer" end of the market and not tech-heads like me. It can be frustrating to be able to tell them more than they can tell me. I'll call LG tomorrow before I place an order for the converter cable. I'll try to get one from within Australia due to consumer laws being more effective for me; although I hope I don't have to return a substitute or fake.
 

hippy

Technical Support
Staff member
I recall earlier PL2303 chips had a fixed PID or required an external EPROM which was probably rarely fitted.

Later PL2303 chip variants have OTP EPROM on-chip but may require more than just the software to program them. For example; "VDD_5 - P - USB Port VBUS, 5V Power. (6.5V for OTPROM writing voltage)" suggest the VBUS supply from the PC may need raising from 5V for programming.

www.prolific.com.tw/UserFiles/files/ds_pl2303HXD_v1_4_4.pdf
 
Last edited:

Goeytex

Senior Member
The latest driver package from Prolific has a utility program that can identify the chip version. Not sure if it can distinguish a fake from a genuine. It identifies the chip in my cheapo adapters as PL2303 XA / HXA. The chip is marked as PL2303HX.
 

inglewoodpete

Senior Member
I called LG's Support line (1300 LG CARE in Australia) earlier today. Level 1 support didn't have a clue (as expected) but referred me to Level 2, who called back 3 1/2 hears later (but they did call back :)).

The L2 support guy had never heard of the feature where a receiver could control the TV via a serial link. My previous LG TV had a DE9 serial port dedicated to this function: this worked well, hence my desire to use it on the new model. This more recent model uses USB to receive the serial commands. I had to get the guy to go to the appropriate page of the user manual to make him aware of the feature (What did I say in my earlier post?). Once I'd convinced him, he checked with his supervisor/colleagues and nobody knew about it or where I could buy a suitable USB/Serial converter cable. I was told that the feature would have been built and tested in South Korea and may not work in LG TVs that use (firmware for the Australian market - my paraphrase). His only suggestion was to go to "computer stores", armed with the manual, and ask if they could supply a suitable converter cable. So much for the 1300 'LG CARE'!

Back from the side issue...

I have checked the USB-to-serial converters of 3 stock lines of 3 store chains and all three use PL2303 chips programmed with the Prolific Vendor ID (0x067B). I suspect the V_ID = 0x0557 is a rare thing. The ATEN UC-232A converters are advertised on the internet, so I'll try my luck with the condition that the V_ID must be 0x0557 with no substitutes or fakes. If I get it to work, I'll probably be the first person in Australia to do so!

Thanks for your assistance/feedback. It is frustrating that an identical pieces of hardware with an identical functions need to have several different ID numbers burned into them for some perceived commercial gain. After all, all the (legitimate) PL2303 chips are made by (or licenced by) Prolific. As Prolific says on their website, they do not make the converters/leads: just the PL2303 chips and drivers. So why the need for multiple ID numbers?

@hippy: Thanks for the link to the official datasheet. I had already downloaded it. BTW the link you provided has a few spurious characters at the end, which invalidate the URL.

Peter
 

hippy

Technical Support
Staff member
It is frustrating that an identical pieces of hardware with an identical functions need to have several different ID numbers burned into them for some perceived commercial gain.
Many would argue the opposite was the real problem; VID/PID often being the same for non-identical hardware ...

After all, all the (legitimate) PL2303 chips are made by (or licenced by) Prolific. As Prolific says on their website, they do not make the converters/leads: just the PL2303 chips and drivers. So why the need for multiple ID numbers?
It is an issue of what VID/PID does or should identify; the product you have in your hand or the component used in that product which interfaces to the USB bus. The USB specification allows it to be either.

Arguably it should be the former so no matter who the product came from you can identify exactly what it is and the manufacturer of it simply by reading the PID/VID. However, what some may call a loophole, allows for the later.

The most likely reason LG specify VID=0557 and PID=2008 is that's the cable they tested their software with and that's what they know works. So that's the cable they coded their software to recognise, and that's what they tell customers to use.

The problem here seems to lie not with Prolific allowing VID/PID to be changed but with LG only accepting a cable with a specific VID/PID.
 

Goeytex

Senior Member
I modified a USB cable to supply 5.0 or 6.5V to a cheapo PL2303-HX Adapter, and then ran the EEWriter Programer. At 5V when READ was pressed, it reported that the EEPROM was not yet Programmed. When a write was attempted, it failed. When 6.5V was applied and a read was attempted it reported "Read Failed". When write was attempted at 6.5V it also failed. Everything failed at 6.5v. The Chip EEPROM could not be written at any voltage.

My best guess is that these Ebay sourced cheapos are fakes, however they work OK in circuit for Picaxe Programming.
 

inglewoodpete

Senior Member
At last, a conclusion to this story. I could only find one supplier in Perth that carries over-the-counter ATEN UC-232A PL2303 converters (there is at least one on-line supplier). Due to the ANZAC day holiday weekend, this afternoon was the first opportunity I had to get my hands on the converter. After purchase, on the counter of the shop, I unpacked and plugged the USB-to-Serial converter into my laptop. The device manager told me the newly inserted USB devices had VID=0557 and PID=2008.

Later, at home, I plugged the lead into the LG TV and there was no error message displayed (no message at all, actually). Some time later, I was able to get a response from my TV after sending a properly formatted command into it. Oh joy, oh joy!!

Thanks to all who assisted and contributed.

Edit 15-May-2014: For those people like me (Eg Googlers) who want to send commands into their LG TV using this USB-to-Serial converter, the serial connection does not perform "perfectly" as per LG's manual. In the end, I had to modify the software in my Receiver/Home Theatre Controller as follows:
  • Send the command as text (LG's manual is a bit confusing). For TV #1 (most people will only be interworking with one TV), send the ASCII character "1".
  • The response from the TV initially works well but responses go awry after a few commands.
  • The TV seems to echo something back after each command, but not matching the manual's specification.
  • I set my controller up to check the response for the two character string "NG". If the controller received a response that did not contain "NG", it treated the response as positive acknowledgement. The "OK" response was not reliable but the commands seem to work correctly.
This algorithm seems to be close to 100% reliable to date.

Peter
 
Last edited:

erco

Senior Member
I have that ATEN UC-232A USB adapter. It was perfect, worked great for many years, but it stopped working on Windows 8, so now it's a paperweight.
 

inglewoodpete

Senior Member
I have that ATEN UC-232A USB adapter. It was perfect, worked great for many years, but it stopped working on Windows 8, so now it's a paperweight.
You'll have to buy an LG TV then :) *. I built a PICAXE-based home theatre controller (HTC) a few years ago and use the ATEN to put serial commands into the TV (Eg select input or divert audio output to the HCT via optical fibre connection).

* Actually, if ATEN are no longer supporting or marketing that adapter then LG are probably using a different interface now.
 

nick12ab

Senior Member
I have that ATEN UC-232A USB adapter. It was perfect, worked great for many years, but it stopped working on Windows 8, so now it's a paperweight.
Did you try the older driver from the PICAXE website?

Older versions of the PL2303 do not work with newer versions of the driver on Windows 8 or later.
 

hippy

Technical Support
Staff member
I doubt if the old Prolific driver will work for an ATEN. While the chip is the same, the USB VID and PID differ.
That might be achieved by adding the appropriate VID/PID to the .INF text file which comes with the driver.
 

erco

Senior Member
I tried everything and still get: This device cannot start. (Code 10) A device which does not exist was specified.

Prolific's chip ID program it says it's the HX version, which isn't compatible past Win7.
 

erco

Senior Member
Update: Based on nick12ab & hippy's comments, I kept Googling this morning and found a 64-bit driver at http://www.totalcardiagnostics.com/support/Knowledgebase/Article/View/92/0/prolific-usb-to-serial-fix-official-solution-to-code-10-error

which gets the ATEN PL2303HX recognized and working on Windows 10, now it works fine with the more finnicky BASIC Stamp 2.

But not with PICAXE. When I do a "check firmware" in Options in PE5 I get

Serial Port Error- code 0x1F54 'Error reading comm device'

One giant step sideways.
 
Last edited:

nick12ab

Senior Member
Prolific's chip ID program it says it's the HX version, which isn't compatible past Win7.
This is forced obsolescence. The HX version is compatible past Windows 7 with old versions of the driver which do not have this antifeature implemented.
 

inglewoodpete

Senior Member
I found that my old Prolific-branded USB-to-serial leads could be kept alive in a Windows 10/64 machine using PL2302 driver version 3.3.2.105. It is a pain, though, because the W10 system updater periodically checks and replaces the driver with a later version.
 

cravenhaven

Senior Member
I found the same problem with my 'fake' PL2303 lead and ended up using an old driver in win10. In addition there is an option to turn off device driver updates in win10 to stop it overwriting the old driver. This has now been working for several months without any problems.
 
Top