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Question about C28346 and GPIO lines (as used Data bus).

Kiseop Yoon
Prodigy 40 points

Hi I'm using c28346(bga type) chip for my custom board which is designed to conduct experiment.

I have a strange problem for using c28346 chip.

I just wanted to know whether the board worked good or not.

So I programmed code and conduct simple experiment. 

The code is like followings

   GpioCtrlRegs.GPCMUX1.bit.GPIO79 = 0;  // using as GPIO

   GpioCtrlRegs.GPCDIR.bit.GPIO79 = 1;  // using as output

   GpioCtrlRegs.GPCMUX1.bit.GPIO78 = 0;

   GpioCtrlRegs.GPCDIR.bit.GPIO78 = 1;  

   GpioCtrlRegs.GPCMUX1.bit.GPIO77 = 0;

   GpioCtrlRegs.GPCDIR.bit.GPIO78 = 1;   

   GpioDataRegs.GPCDAT.bit.GPIO79 = 0;

   GpioDataRegs.GPCDAT.bit.GPIO78 = 0;

   GpioDataRegs.GPCDAT.bit.GPIO77 = 0;

I expected  the result as 0, 0, 0 for GPIO79, GPIO78, GPIO77 respectively.

but the result was strange. Only GPIO78 had the value 0. and GPIO79 and GPIO77 had the value 1.7(V)(about half of 3.3 V) when I estimated them with voltage scope.

So I conducted experiments with other GPIO lines (64~79) and found the followings.

Only GPIO79, GPIO77, GPIO75 had the wield value (1.7(V)).

I tried all other thing which I could do but I can't find out the reason..

Please help me to solve my problem... 

Ps. I must use the lines (GPIO79, GPIO77, GPIO75) because I have to use (16bit) data bus..

  • 0
    TI__Guru 71785 points

    Kiseop,

    You are correct, that this should not be the case, from your explanation it looks like there is contention on the GPIOs that are not @ 0V.  Can you advise if you are using control card, or your own PCB.  I would make sure with whatever schematics that there is not another active component on the bus.  If this is a standalone device, then the device might be damaged and will need to be submitted back to TI for FA.  I will look for your answer for the above and we can see the best way to proceed.

    Best,

    Matthew

  • 0 in reply to MatthewPate
    Prodigy 40 points

    Hi thanks for your answer. I still can't resolve my problem... I want you to know the followings and hope that makes the situation better.. 

    First, I use my own PCB which is modified from control card(c28346 development kit).
    Second, I found the fact that when I read data from 'Zone 7' or 'Zone 0', data lines (XD0, XD2, XD4) worked fine..
    ex) Write and read operation : XD0, XD2, XD4 : '1' only
           Read operation : XD0, XD2, XD4 : '0' and '1'. works fine.

    Third, the Data line connected between 4 chips, C28346(DSP), CY7C1041V33CC (SARAM),  FT2232H(for USB), 74LVC16245a (transreceiver). 

    Thanks.

    Ps. I also insert my schematics which contains 4 chips connected by Data lines

    3513.SCHEMATIC1 _ 01 - MCU.pdf

    0081.SCHEMATIC1 _ 04 - FT2232H.pdf