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TM4C123_LaunchPad: "**ERROR**: Cannot find target device"

Robert Samuel
Intellectual 610 points
Other Parts Discussed in Thread: LMFLASHPROGRAMMER

I would greatly appreciate help with a nasty problem: I have locked-up a TM4C123_LaunchPad connected via USB to my Windows PC (64 bit, Win7 Pro). The
IDE I am using is Keil uVision4. This happened while I was "experimenting" with configuring GPIO ports on the LaunchPad.

After spending all day today trying to sort this out I finally found Sue Cozart's TI E3E Community "JTAG Communication Failures" post (Dec 19, 2013 3:56 PM).
The item "2. Changing the function of the Port C[3:0] pins, which are muxed with the JTAG pins.", hit home as I was attempting to use PORTC. Once I loaded
the code with the PORTC configuration code, in to the LaunchPad it stopped communicating.

I have tried using the LM Flash Programmer with no success. Clicking the "Debug Port Unlock" in "Other Utilities" results in the following message: "**ERROR**
Failed to unlock connected device!". Clicking "Hardware" button in the "Program" tab results in: "**ERROR**: Cannot find target device". BYW, I don't have the
MAC address for the board as it's not communicating.

Part of my "experiment" program loaded and is partially working, the on-board green LED on PORTF cycles on-off when the reset button is pressed. However,
there is no output on pins on PORTB and PORTC. All the drivers are installed and were functioning prior to my "experiment"!

All help will be greatly appreciated.

Thanks, Bob

  • 0
    TI__Guru**** 244410 points
    Hello Bob,

    The TM4C123 does not have a MAC so it is not to be considered here. The steps to unlock require that the reset be pressed when the board is powered up. With the reset pressed the LMFlashProgrammer Sequence needs to be done. Only when the LMFlashProgrammer tells to release reset, should the user release the board from reset and then power cycle the part.
    Do make sure that the Device Manager in the PC shows Stellaris ICDI as the ICDI is the one which interprets the LMFlashProgrammer to unlock the Main MCU.

    Regards
    Amit
  • 0 in reply to Amit Ashara
    Intellectual 610 points
    Amit, thank you.

    I will give this procedure a try and then let you know if it works.

    Bob
  • 0 in reply to Robert Samuel
    Intellectual 610 points
    Hi Amid,

    It worked thanks! One additional problem. I have two development machines.

    Machine #1, the one that I was using when I created the lock-up problem, now loads the "Silicon Labs CP210x USB to UART Bridge" driver when I connect the newly unlocked LaunchPad, not the "Stellaris Virtual Serial Port" driver. I did a lot of playing with drivers trying to solve the lock-up problem, the "Silicon Labs CP210x USB to UART Bridge" driver was one of them. I have uninstalled it, however it keeps coming back!

    However, machine #2 loads the "Stellaris Virtual Serial Port" driver when the LaunchPad is connected. This system now works without problem.

    If you have the time I would appreciate your advice.

    Thanks again, Bob
  • 0 in reply to Amit Ashara
    Intellectual 610 points
    Hi Amid,

    It worked thanks! One additional problem. I have two development machines.

    Machine #1, the one that I was using when I created the lock-up problem, now loads the "Silicon Labs CP210x USB to UART Bridge" driver when I connect the newly unlocked LaunchPad, not the "Stellaris Virtual Serial Port" driver. I did a lot of playing with drivers trying to solve the lock-up problem, the "Silicon Labs CP210x USB to UART Bridge" driver was one of them. I have uninstalled it, however it keeps coming back!

    However, machine #2 loads the "Stellaris Virtual Serial Port" driver when the LaunchPad is connected. This system now works without problem.

    If you have the time I would appreciate your advice.

    Thanks again, Bob
  • 0 in reply to Robert Samuel
    TI__Guru**** 244410 points
    Hello Robert,

    These installers are little troublesome and you may need to change the driver to pick Tiva drivers by asking it to always select the Tiva drivers. I wish I had a snapshot of it when I had to force the PC to take an older version of TM4C drivers, I do know there was a thread on the forum where the steps were mentioned to pick a particular time stamped version of the driver.

    Regards
    Amit
  • 0 in reply to Amit Ashara
    Intellectual 610 points
    Hi Amid,

    Thanks for the insights. I'll go search for for the post you suggested.

    Thanks again for all your help.

    Bob
  • 0 in reply to Robert Samuel
    Guru 56043 points

    "**ERROR**: Cannot find target device".

    LM Flash programmer is really fast on the target USB connection after U click program and the Target DAP might otherwise be unable to respond if the background function is taking 100% MPU time.

    Try holding reset down on the MPU, wait at least 500ms after releasing reset before clicking Program. Do this several times in a row using both arms and finger. Betting your brain is faster than the MPU one reset program cycle will break into the looping cycle runaway function and program the target.

  • 0
    Guru 56043 points
    >>The item "2. Changing the function of the Port C[3:0] pins, which are muxed with the JTAG pins.", hit home as I was attempting to use PORTC. >>Once I loaded the code with the PORTC configuration code, in to the LaunchPad it stopped communicating.

    Those JTAG lower pins on port C are protected and require an unlocking code when programming the GPIO order to change default setting. Unless U provided an unlocking code when setting GPIO port C pins it is unlikely they were changed and still support JTAG.

    Amit offers several good solutions - I have noticed the wacky hold reset message makes no sense and often works backwards. Sometimes when the DAP is locked you have to also screw around with how fast and when you click unlock also a two arm 2 finger event. Bill Gates moves!