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EK-TM4C1294XL: Connecting the board to a TTL logic system via a level translator board

Charles Moori
Prodigy 250 points
Part Number: EK-TM4C1294XL

I have a project to connect the TM4C1294XL board to a TTL logic system. I have designed a level translator board using 74FCT164245 chips. The Level translator board provides Vcc = 5V and also 3.3V power.

At this time I am using the CCS for debugging and connect the TIVA board to PC via the debug USB port . My question is if I may (should) connect my +5V and +3.3V to the TIVA board (i.e. pins 1 and 2 on X6 and X8 ports or just have common ground and let the USB port feed the TIVA board and the +5V and +3.3V on the level translator board should fee ONLY the part of my system. I hope I described my problem properly.

Thank you

Charles

  • 0
    TI__Guru**** 191256 points
    Hi,
    I think you just need to maintain a common ground if your JP1 on the EK-TM4C1294XL board is configured to take power from the USB debug port.

    In case you haven't seen it here is the user's guide for the EK board. The schematic of the board is at the end of the document. www.ti.com/.../spmu365c.pdf
  • 0 in reply to Charles Tsai
    Prodigy 250 points
    Thank you Charles.
    I have the documentation, and I really got confused checking the schematic. I did not find explanation of the jumper settings, and I am not really familiar with the acronyms (like OTG etc.) To me looking at the board the Booster Pack term does not say too much. I am working on a project, and to tell you the truth, I do not have time to study an over 1800 pages documentation or study to the smallest details a 6 page schematic. I did not even found where the 3.3V comes from when I connect the board to the PC via U22 (I just guess this is the DEBUG VBUS signal). I am working on a completely different area, and I am not familiar with the terminology I found on the schematics. I am sorry about.

    Thank you

    Charles
  • 0 in reply to Charles Moori
    TI__Guru**** 191256 points
    Hi,
    The default position of JP1 will source power from the Debug USB port. Therefore the power comes from your PC. I think you will be fine with this default selection for your development using the LaunchPad.
  • 0
    Guru 55913 points

    Hi Charles

    Charles Moori said:
    The Level translator board provides Vcc = 5V and also 3.3V power.

    Common grounds as Charles states are required no matter how you power the two PCB.

    One would hope jumpers can disable supplies on LTPCB and never power LTPCB before the launch pad EVM.

    Either pulling JP1, JP3 plugs and powering both PCB together from ONE source ensures you don't forget proper order powering down as well.

    Charles may have more info why order of powering devices is important to keep in mind as not to accidently degrade GPIO ports performance.

  • 0 in reply to Genatco
    Prodigy 250 points

    THANK YOU BP101,

    I have removed the jumpers JP1 and JP3, and fed the TI board from my level translator board (providing both +5V and +3.3V to the TI board and now two boards what were down (nor being able to to connect to PC from USB port, even being stand alone) now working from one single power. I think this solution should make wide known as I believe it was not only me who had this problem. AGAIN, Thank you very much for your advise and help

    Your sincerely

    Charles

  • 0 in reply to Charles Tsai
    Prodigy 250 points
    Thank you Charles for your help,
    I have removed JP1 and JP3 (according to your and BP101 advice) and fed the TI board and my unit from common power. Now two boards what were not able to connect to the PC, now working. I believe this was not only my problem so it has to be spread wide that if possible feed the TI board and the connected to it other units from ONE only power supply (BOTH +5C and +3.3V).
    Again, thank you for your help

    yours sincerely

    Charles
  • 0 in reply to Charles Moori
    Guru 55913 points
    Hi Charles,

    The idea with resolved button is to give helpers reward of resolved. Happy to hear your LTPCB & EVM powers up/down together, best practice!