Electronic – arduino – Mirror-inverted and wrong-colored display

arduinotft

I'm trying to address a (cheap chinese) ILI9320-driven 320×240 LCD display from an Arduino Mega 1280. I've got it to work via the UTFT library. Well, not fully; something is shown, but the colors seem a bit faded and wrong, and the display seems to be mirror-inverted (the letters printed on the screen by the example programs from UTFT library at least are).

Supposedly this is the documentation of the display I'm having.
I'm running it from an Arduino Mega 1280, the example given on the documentation page is for the Mega 2560; could that be the reason for my problems?
I connected all the pins (RST, RS, WR (actually called RW on my display board), RO, and DB0-DB7 according to the above documentation:

RS -> D38
WR -> D39
CS(pin6) -> D40
RSET-> D41
RD -> 3.3V
DB0->DB7 to D22->D29

Double-checked all these connections so they should be connected where the docs say they should.

I first had 5V and Gnd also connected; but since the above pin mapping doesn't mention them at all, I tried without them, and noticed they weren't needed – the display also shows something without them connected, although disconnecting Gnd makes the image a little darker. Could I have blown the screen circuits somehow by that? Should I connect 5V?

Here are some example images of how it looks like:

From the demo program (Bitmap from UTFT): Supposed to be properly colored Tux'es and happy faces in various sizes I guess:
From the demo program: Supposed to be properly colored Tux'es

Supposed to be a red rectangle with the text "Hello World" across, shown via the same method as in the "Bitmap" demo program from UTFT):

Any ideas what I'm doing wrong here?

Something I forgot to mention in the start (but which might be very important!):
In the example code, I tried to use myGLCD(ILI9320,38,39,40,41) for initialization as mentioned in the documentation, but ILI9320 does not seem to be defined in the version of UTFT I'm using (and also isn't mentioned anywhere in the comments in UTFT.h, only ILI9325D), so I tried ITDB24D; I played around with the possible value there a little but haven't tried all possible values, maybe I just haven't found the right one yet? Anybody knows what the proper value to use is, or where ILI9320 is defined?

Best Answer

Assuming that your wiring is correct: have you tried to enter myGLCD(GEEE24,38,39,40,41) ? This is for the ILI9320 controllers. It's writtien in the PDF in the UTFT folder. I tried the same module and for me the image just turned out to be mirrored with a lot of flickering (but with proper image quality) until I found out that defining the controller as ITDB24D solved all problems at once. Therefore the controller inside (in my module at least, as the vendor stated) really seems to be an ILI9325...confusing, but my module is working now (with a mega2560 and 5V supplied). I only had to calibrate the touch screen.

Related Solutions

Electronic – arduino – Identifying Pins of an Unknown LCD

This is a pretty common pinout for an LCD. You can be pretty confident that it uses the Hitachi HD44780 chipset. The LiquidCrystal library should be able to drive it without any trouble. The K and A pins are just backlight power pins.

Any digital pins should work... just make sure you connect the pins to the LCD the way the comments in the example suggest. You just need to map the pins you are connecting to the signature of the constructor being used in the example.

lcd(12, 11, 5, 4, 3, 2);

is using the constructor from the library docs that goes with:

LiquidCrystal(rs, enable, d4, d5, d6, d7)

You know this by counting the number of arguments. So in the example:

Digital 12 == RS == LCD pin 4
Digital 11 == Enable == LCD pin 6
Digital 5 == D4 == LCD pin 11
Digital 4 == D5 == LCD pin 12
Digital 3 == D6 == LCD pin 13
Digital 2 == D7 == LCD pin 14

You obviously also have to connect LCD Pin 2 to 5V and LCD Pin 1 to GND. You may also need to hook up a potentiometer to LCD pin 3 to adjust the contrast. Which may be the problem you are describing in your comment to me above. There are literally hundreds of tutorials on line about this, use the google :).

Electrical – No PSB pin on LCD

Many LCD controllers (including the ST7920) can support a variety of interface types, of which you can use one at a time. Sometimes the interface type is fixed on a given LCD display module; sometimes the interface can be selected. The exact PCB markings for selecting between interfaces (when possible) does not always match the signal names you are expecting.

Since the interface is not always able to be selected, then the answer from Finbarr is sometimes correct - you might find that the interface is absolutely fixed (e.g. parallel-only, SPI-only etc.) on a given LCD module.

However in your case, I think you might be lucky. I noticed a similarity between your LCD module, and the one used in the first tutorial which you linked.

Notice how your LCD module has the part number 14432D on the back, and we see 2 component locations - R11 and R12. R11 is missing and R12 is fitted:

Now look at this image from the first tutorial that you linked, showing the back of that LCD module (which is different to your LCD module, and hence there is no guarantee that the first tutorial you linked would apply to your LCD module anyway). See that it has the same component arrangement as your LCD module and also has an R11 and R12. Except on that module, R11 is fitted and R12 is missing:

I cannot guarantee that this next part applies to your LCD module - you need its datasheet with the relevant details to be completely sure. However it is possible that the answer is contained in this document:

Notice how for their model number ending 14432D (similar to your model number), the resistors R11 and R12 are used to select between parallel and SPI interfaces. On the LCD module in your first tutorial link, see how only R11 is fitted, and they are using the SPI interface. On your LCD module, see how only R12 is fitted and you are unable to use the SPI interface pinout as shown in that tutorial.

So perhaps your LCD module is configured for a parallel interface? That would be consistent with the fact that R12 is fitted on your LCD module.

Therefore perhaps by desoldering R12 from your board and resoldering it in the R11 position, you may be able to use the SPI interface and pinout shown in that first tutorial.

Update:

Here is the PCB after Fusseldieb made the modification (the resistor was moved from the R12 position, to the R11 position):

That modification was confirmed to successfully enable the SPI interface, using the following connector pins:

LCD Pin   SPI signal   (Original)
-------   ----------   ----------
   1        Vdd          (Vdd)
   2        Vss          (Vss)
   3        Vo           (Vo)
   4        CS (SS)      (RS)
   5        MOSI         (R/W)
   6        SCLK         (E)

FYI, looking at the other tutorial:

http://www.arduinoecia.com.br/2013/09/display-grafico-lcd-128x64-st7920.html

That uses an LCD module with a completely different interface pinout, which includes the CS1 and CS2 signals (pins 15 & 16 on its 20-pin connector). This allows the interface to be switched between parallel and SPI without needing to solder/desolder components on the PCB. You don't have that 20-pin connector with those signals on your LCD module. That is why that tutorial does not directly apply to your module (although the ST7920 commands will likely apply, once you can get an SPI interface working on your specific LCD module).

Best Answer

Related Solutions

Electronic – arduino – Identifying Pins of an Unknown LCD

Electrical – No PSB pin on LCD

Related Topic