LCD troubles

I think have mentioned before that I have special service jig that allows me to test every single LCD before posting it with the kit. It is very useful idea, as it saves money and hassle in the long run.

The usual QC fail on every batch i get is in the range of 10-20 %. And the most common fault is the famous ‘White Screen’ problem. I haven’t done any detailed analysis, but i would say is either badly soldered flat cable/mode jumpers or simply faulty controller chip.

white_screen

But testing my latest batch i got more than 55% failed LCDs. And the ‘fault’ was not the usual ‘White Screen’ but something i call ‘Broken TV’, something you would get on old school analogue TV without an antenna connected.

broken_tv

It was really concerning, so after speaking with the manufacturer, it would seem there are four different revisions of the ILI9325 controller chip, named by them as A,B,C and D. There is a differences between them, not a detailed list of those, but one important thing would be the maximum communication speed. It would appear that version A is the slowest (not being able to handle higher clocks) and D is the fastest.

So using the 0.219.26.4 version of the source code and latest driver source code for the controller from the manufacturer i was able to make those LCDs, that have the new revision controllers work.

You can find the updated firmware binary on my Downloads page, and source code fork is on my GitHub account.

Chris

6 thoughts on “LCD troubles

  1. Kees Talen

    Hope this does not confuse anyone …..the net is that the driver code must match the hardware spec.

    Yes, dealing with China vendors is “inexpensive” ….but very frustrating and impacts your great ham radio product. Let me relate our experience and what was found (we provide the AQRP VIA kit which uses a TFT 320QVT color touchscreen display).

    Most of the sellers are just resellers and don’t actually manufacture the displays. Many don’t fully understand their product. They will ship what they have, REGARDLESS of what the ebay picture shows or writeup says. As their supply source is updated with the latest manufacturer’s changes, they just change…..poof. You have to remember that the manufacturer’s REAL customers are smart phones, etc with HUGE volumes. I think the excess stock (maybe rejected batches ?) go to the resellers on ebay.

    The TFT320QVT was originally supplied with the SSD1289 controller and we had a few (10%) “white screens” and ALL TFTs had to be fixture tested. Yes, we also had ~2% “duds” ……no screen at all, lines on the display. It was thought that the “white screen” was a power sequencing, voltage level, initialization, or just a timing problem since we are also using the STM32F407-Discovery board, which is quite fast. Some of the microcontroller timings were changed and finally ALL the TFTs with the SSD1289 controller worked.

    Fast forward a hundred TFT batch orders, and the sellers changed to the ILI9341 controller “which works just the same”…..the seller says

    NOT SO. Nothing worked, not a one of the 20 that I had ordered. Not all the displays using the SSD1289 worked either (but we had a timing fix for that), so I ordered more of those from the info on ebay. All those arrived with ILI9341 controllers……..so much for “accurately described”. The ILI9341 controller is the newer one and what everyone will now receive, thank you very much. So we HAD to make the new controller work.

    It turns out the real problem is the controller driver code which we normally just pick up. Milt dug through the ILI9341 hardware specifications data and the ILI9341 driver code and found several discrepancies where they violated the ILI9341 hardware specifications. I’m sure the smartphone people have discovered and corrected all this but they don’t share info with old retirees. After much experimentation (we’re Engineers not seasoned Programmers) the discrepancies were fixed and the new firmware works fine. We even have a flag which is set, if the earlier SSD1289 controller is sensed, and automatically switches to a DIFFERENT TFT driver. Great work Milt !

    All this was a WHOLE lot more work than this small team of retirees had anticipated. But so far, we won.

    Reply
    1. m0nka Post author

      Hello Kees,

      Yeah, that seems to be the case with everyone. Only difference here is that i think i buy from the manufacturer, or at least he claims that. Also i will wrong him if i say that he was not helpful, he always did replace faulty ones, it is just this once, he insisted i need to update my driver.

      Also it is fortunate for me that i am no engineer or programmer, i am hardware hacker. I have been doing Reverse Engineering for a living for some time, so you can’t easily scare me with lack of documentation or source code.

      I think the main problem is that we all go for the cheapest deal, i guess would be possible to get properly made LCD, with good documentation and support, but the price will be 10x what we get those ex Windows Mobile 2003 screens, aka year 2002.

      Good luck on you project!

      73, Chris

      Reply
      1. Kevin

        Any information about a good ebay supplier of a compatible touchscreen – or a part number that can be substituted for the HY28B?

        Reply
        1. m0nka Post author

          Hi,

          Sorry, i have no idea. It is becoming difficult to source even from the manufacturer and even with them there is 10-20 % failure rate
          on the LCDs i receive 🙁 It has been few years and the quality seems to drop.

          Chris

          Reply

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