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I2C port stubbed out header for future LCD etc.. has +3v3, RST - other GPIO's need be added?

Genatco
Guru 55913 points
Other Parts Discussed in Thread: TM4C1294NCPDT

Not much experience with LCD just yet but figured it was good to provision an I2C header for future IO fan out from the PCB.

Have ST discovery board with nice color LCD picked up some time ago. The schematic shows I2C3 and GPIO pins AFSEL what appears to be SPI port into the LCD control module SF-TC240T-9370-T.  Possibly the SPI port is equivalent to EPIO with fewer port pins enable.

The TM4C1294NCPDT datasheet details of the I2C peripheral suggest it can be used for LCD etc.

The driver signals of the LCD:

MPU - SPI signal names: DotClock, Vsync, Hsync SDA, Enable, CSX, RDX, WRX DCX, DCX_SCL, TE.

MPU I2C3 decoder IC input signal names: SCL, SDA, INT1

1. Does color LCD require more signals than non color, does that make a difference?

2. Do most all LCD modules require more than just an I2C data port for text versus graphics modes?

Thanks for any ideas or suggestions, the PCB is tight on routing and header space.

  • 0
    TI__Guru**** 244400 points
    Hello BP101,

    The data sheet of the display controller on the LCD SF-TC240T-9370-T is not clear as to what is SCL. Also if you look at the IMx decoding the SDI and SDO pins are mentioned but the pin out does not show which pin is SDI and SDO.

    As for the questions
    #1: That depends on the controller on board.
    #3: Again depends on the IMx decoder for the specific LCD. In some cases it called PSx pins.

    Regards
    Amit
  • 0 in reply to Amit Ashara
    Guru 55913 points
    They must have renamed SDI/SDO but are serial data in/out.
    SCL/SDA is pin 37/30 and both feed into demux matrix STMPE811QTR dump into 1,2,3,4 of 9370-T.

    So then it requires more than MPU serial data In/Out to get an LCD to work properly?
  • 0 in reply to Genatco
    TI__Guru**** 244400 points
    Hello BP101

    Pin 37 is marked as DCX. The serial port can be used (SPI) which is the case on the kentec's new panel based boosterpack.

    Regards
    Amit
  • 0 in reply to Amit Ashara
    Guru 55913 points
    Hi Amit,

    That SCL is marked DCX_SCL in the schematic so expect to be the same. Unfortunately the TM4C1294 don't have a SPI port but isn't that the same as EPIO surely not SSIO?

    The datasheet suggest the I2C port can drive an LCD. Was the Idea for I2C to use EPIO or GPIO to drive XY vector graphic coordinates decoder and provide all the other signals mentioned in first post?

    Again may omit I2C if to many signals are required as not much route space is left around the MPU.
  • 0 in reply to Genatco
    TI__Guru**** 244400 points
    Hello BP101,

    Can you send me the link to the schematics as it is not clear to me which schematic you are referring to.

    The TM4C12x devices have SSI as the SPI port function.

    Again panels come in all shapes, sizes and flavors. As you would be knowing by now that the LCD controller on the TM4C129x class devices offload the parallel work while SPI offloads the serial port requirement. So if EPI or GPIO is required, then it would depend on what kind of control is required that a LCD and SPI cannot do.

    Regards
    Amit
  • 0 in reply to Amit Ashara
    Guru 55913 points
    Hi Amit,
    Suppose that might be relative to the LCD graphic driver library and or software examples that are used in driving the LCD whether GPIO or EPIO port pins are required?

    Back in the day a CRT only required H/V-sync and dot video for vector graphics displays. Seem to recall seeing TI has an LCD equipped launch pad TM4C1294 alternative but in a Ball pin layout. Might that be a better choice to get examples of LCD attachments?

    www.st.com/.../PF259090
  • 0 in reply to Genatco
    TI__Guru**** 244400 points
    Hello BP101

    Yes, it could be that the drivers are developed for specific panel requirement in this case as per ST's platform document it is not even clear what interface it is. We have supported SPI based panels on TM4C123 and LCD/SPI panels for TM4C129x family of devices.

    Regards
    A,ot
  • 0 in reply to Amit Ashara
    Guru 55913 points

    Hi Amit,

    That is a color touch screen similar to DK-1294 development kit. The ST LCD has an on board processor and uses parts of 3 GPIO ports to form what they call SPI3.

    Seems as if more high level engineering work need be done order to reduce LCD drive signals to a moderate 4 wire configuration. The I2C peripheral discussion in the datasheet TM4C1294NCPDT leaves out details of what other ports also need to be enabled to make an effective LCD driver I/O.

  • 0 in reply to Genatco
    TI__Guru**** 244400 points
    Hello BP101

    I2C, SPI and UART are very generic protocols. It is not possible to bind them to operational use with respect to a particular end slave device and no manufacturer would do so to a "generic" module. They will only emphasize their specialized additions (mktg)

    Regards
    Amit