I'm trying to build a HDMI decoder board for a 4in 480x800 IPS display. I found an HDMI decoder board on adafruit(https://www.adafruit.com/product/2218) which says it works for most 40pin TTL displays.

The display I'm intending to use has 51 pins and says it has an RGB/MCU interface.

I'm trying to look at the schematic and see if I can modify it and make a board that accepts the additional pins of my display but I'm not sure what the difference is between MCU and TTL?

I know the chip used on the adafruit decoder board (TFP401) supports both screens since I have an off-the-shelf 4in IPS display that uses that same chip.

Here is the datasheet of the display I plan to use: https://www.scribd.com/document/383775532/4in-IPS-display


closed as unclear what you're asking by Chris Stratton, Dmitry Grigoryev, Voltage Spike, Bimpelrekkie, filo Jul 19 '18 at 13:09

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    \$\begingroup\$ Datasheet of the display you plan to use? "RGB/MCU" isn't specific enough to guess what each of these 51 pins is. \$\endgroup\$ – dim Jul 12 '18 at 20:49
  • \$\begingroup\$ @dim here is the datasheet - scribd.com/document/383775532/4in-IPS-display. Thanks for having a look \$\endgroup\$ – shekit Jul 13 '18 at 9:21

The RGB interface means your display will use some of the pins to input 24-bit RGB color data and some control signals. The Adafruit board supports an RGB interface.

Some displays also have a MCU interface option where a parallel or serial bus is used to access frame buffer memory in the display itself, for drawing pixels, lines, etc. under software control. As you are using the RGB interface you don't have to be concerned about this. It just means your display can use either interface depending on the application.

On your display's ribbon cable there will be several pins used to select which interface to use. Pull the pins high or low (as documented in the display datasheet) to select the RGB interface. While you'll need to check the display datasheet and compare it to the Adafruit schematics and TFP401 datasheet, most likely the signals used by the RGB interface will be a 1:1 match between the the display and board.

  • \$\begingroup\$ ok this makes it much clearer. I had a look at the datasheet(attached above) and it has two pins 47(IM0)/48(IM1) and from what I understand from it, if both are 1(high?) then the interface is RGB? \$\endgroup\$ – shekit Jul 14 '18 at 4:14
  • \$\begingroup\$ Yes that sounds correct. Connect them to the same source as pins 6,7 which is likely 3.3V for your application. The datasheet for the controller IC embedded in the screen is here if you need more information: hands.com/~lkcl/eoma/shenzen/frida/… \$\endgroup\$ – user185972 Jul 16 '18 at 15:45

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