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Programming external Tiva using Launchpad

Bryson Barney18
Prodigy 10 points

Hi,

I am using a Tiva C Launchpad to program an external TM4C123G (same MCU found on the lauchpad).  I am able to program is once (using CCS), but it does not pause or debug correctly.  If I try to program it a second time with CCS it reports "CORTEX_M4_0: Error connecting to the target".  If I use the LM Flash Programmer to Unlock it, then I can program it once again before being locked out again.  Does anyone know what is going on here?  I have the TCK, TMS, TDO, TDI, GND, and reset pins connected from the launchpad to my board.  I also have the VDD jumper removed on the launchpad so that it doesn't talk to the onboard MCU.  I also have a VDD connection from my board to the launchpad for power.  Any help would be greatly appreciated.


Thanks,

Bryson

  • 0
    Guru 117855 points

    Bryson Barney18 said:
    I also have the VDD jumper removed on the launchpad

    I'm not so sure that the "VDD jumper" removal is proper.   Instead - there is one pin which holds the "target/on LPad" MCU in Reset - so that "it" is blind to the programming transactions.

    From your (decent) description - it may be that there is contention between the "target/on LPad" MCU and your external MCU.

    Have you included (external) pull up Rs on each/every JTAG pin - on your external board?   Indeed MCU manual notes "internal pull-ups" - these are too high in value to insure proper square signal edges - repeatedly my firm finds/fixes such (use the internal ones) failures!

    You should monitor the 3V3 during the programming process as well.   (watch for dips/noise)

    Short, sweet connections between the LPad and your new board always help.

    A more robust/SERIOUS (i.e. J-Link) JTAG/SWD probe really helps and is available @ great discount via "student discount."   (even for those Non students!) 

    (hundreds here crash/burn regularly - just like you - using cheap/dirty LPad as JTAG probe)