EK-TM4C123GXL: LaunchPad not turning on/ being recognized by computer

Jesse J said:

the green pwr indicator LED blew and began to smoke.

That's unfortunate - feel your pain - yet (much) of that damage could have been prevented!

1. ALWAYS - the 'Correctness of the Power Source' should be 'Confirmed' - prior to the connection.   It is believed that your 'battery source' (likely) survived - what is the voltage output?   (and - does that (near) match the battery's specification?)
2. WHERE did you apply the Battery's (+) lead?    If you connected to the '3V3' pads on the board's headers - and the battery voltage was, 'Much Above 3V3' - it may be (unfortunately) that 'Destruction Expanded beyond your hapless green Led!'   (i.e. potentially to the MCUs (both of them) thus Disaster.)
3. A multimeter set to 'Resistance' can measure between 3V3 and Gnd and also between VBus & Gnd.   Do report those results.
4. Identify the position of the slide switch (Device or Debug) during the 'Battery Interlude.'

Based upon these measurements - it (may) be possible to repair your board @ minimal cost - yet it is premature to 'Raise Hope.'

BTW - even if you mistakenly, 'Applied 12V to the '3V3 Bus'

• only 12V minus the Led Drop (~2V) thus ~10V
• passed thru 330Ω - yields (just) 30mA - which (may not) prove sufficient to 'KILL' that green Led!
• instead - that hapless '3V3 Voltage Regulator' - was far more likely - to have emitted: light/heat/smoke
• And - if fortune shined - that destruction (may) have 'clamped down upon your battery voltage' and (maybe) saved (both) the ICDI & Target MCUs!

Follows now a 'Guiding extract'  from the '123 LPad's schematic' (contained w/in the '123's LPad User Guide.'

Introducing external power into (any) of the board's '3V3' marked header pins is (almost) certain to 'destroy' the board's Voltage Regulator (U8)!

The LPad's spec notes that 4.75-5.25V is the 'acceptable' voltage input - again (introduced via 'VBus') when externally (non USB) powered.

Note: 'VBus' appears at, 'Pin 1 of the 2nd (leftmost) column of header pins.'   (when board is oriented w/ICDI MCU up top)

Bob Crosby said:

If the green LED (D4) smoked,

And that 'Destruction of the LED' may be subject to debate!    Here's my case:

• That LED (D4) is exactly 3mm distant from the voltage regulator - and as earlier noted - w/current into the LED limited by R27 (330Ω) - destruction is unlikely to be immediate.
• We've no 'assurance' that the (likely) excessive battery voltage was applied to the 3V3 rail.   If applied to VBus - the regulator (itself) 'May have failed open - extinguishing the LED' - while emitting smoke!

Kindly note that I 'made no claim' for the board's 'clear-cut' survival.   My quotes:

• "it may be (unfortunately) that 'Destruction Expanded beyond your hapless green Led!' 
• " it (may) be possible to repair your board @ minimal cost - yet it is premature to 'Raise Hope.'

What I did suggest was the, 'Quick/Eased' probing of the board - which costs 'little' in time/funds/effort - and is likely to encourage, 'More careful board handling behavior' in the future...

Note too - it has not been determined that the battery 'improperly' connected to the 3V3 power rail.   Destruction may have occurred if the battery was introduced upon 'Header pin 'VBus' or via a 'hacked' USB Cable - when inserted.    Should the battery voltage have:

• been applied to VBus
• and exceeded the VReg's 'Max Input Voltage Rating' - the VReg likely failed - and (if it failed 'open') perhaps, 'No destructive voltage 'passed thru' to either MCU!

ALL of the facts must be known - and admitted into evidence - prior to 'logical conclusions being formed & properly verified.'    I believe the 'key conditions' have been identified - and these initial conclusions are systematic & logical - yet await poster's, 'Introducing the requested details.'

I connected the positive(+) terminal of the battery pack to the VBUS pin and the negative(-) to the ground pin. The battery source connected was a holder that held six AA batteries. The resistance between 3.3V and GND is 3.0 and between VBUS and GND it reads a little under 200 ohms and then stops reading. The switch was in the debug position when the LED popped.

I think the green LED on my board is D2: it lies between R27 and R19. Also, I connected the power source to VBUS not 3.3V

Greetings,

Thank you - you've answered 

Jesse J said:

I connected the positive(+) terminal of the battery pack to the VBUS pin and the negative(-) to the ground pin.

Excellent - that reveals a 'considered application of battery power' - but for the (likely) battery voltage EXCEEDING the board's 4.75-5.25V ABS. MAX. rating!

Jesse J said:

The battery source connected was a holder that held six AA batteries.

Pardon - the description of '6 AA batteries' proves, 'Not Definitive!'   Here's why:

• Those 'AA' batteries could be: Alkaline, NiMH, or (even) Lithium.   Different voltages are produced by 'differing battery chemistry' - are they not?    If your batteries are alkaline - and fresh - the output voltage should be ~9VDC.    If NiMH - -  ~7.2V - it is (unfortunately) believed that 'either' voltage exceeds the input capability of your board's VReg!
• It is 'normal/customary' for such 'battery holder' to, 'Connect the batteries in Series' - yet you should confirm that as fact.   (my firm has such holders which are able to 'parallel connect' - while (somewhat rare) it is 'w/in the realm.'

Jesse J said:

The resistance between 3.3V and GND is 3.0 and between VBUS and GND it reads a little under 200 ohms

Can you confirm that those measures were performed w/your (likely) DMM's ground lead tied to 'board ground?'    Between 3V3 & Gnd - does '3.0 mean 3 ohms?   (i.e. what scale was employed?)

We've tested 3 of our boards - VBus to Gnd is in the MegOhms, 3V3 to Gnd is ~65KΩ.    And our board - like yours reveals 'D2' to be the 'Power Monitor' - although ours is yellow (on 3 boards.)   LED D1 is multi-color & located just beneath the Reset Switch.

*** There IS a key action you can take - which (likely) will reveal if your 'Target MCU' (U1) has been damaged!    Just beneath the VReg is a, '1x2 header' w/a removable jumper.    When that jumper is removed - you 'isolate' MCU U1 from the board's 3V3!    You may then measure the resistance between U1's 3V3 (which is accessed via the 'right side pin' of the 1x2 header) and Gnd.    (the left side of the header ties to board's 3V3 - output via the VReg.)    Should that right side pin also suffer low resistance to ground - then your target MCU is (almost) surely destroyed.    Again this method nicely reveals if U1 (your target MCU) has been damaged!

It may also prove useful to have U8 (the VReg) professionally removed - and then check for 3V3 to Gnd resistance.