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TM4C123GH6PM Power Supply in Device Mode having erroneous data output

Lili Andrea Pinero
Prodigy 40 points

I'm using  TM4C123GH6PM as a microcontroller for this energy project I'm making.  I use it to collect voltage and current readings. Another device called TelosB is connected to the Tiva board using UART interface to gather/transmit data. These readings are then received to a base station mote (also TelosB).

When I use Tiva with my PC in debug mode, everything is working smoothly, the values I gather are correct. When it reads 220V in the IAR watch (debug), the base station also receives 220V. However, I want to make it stand alone and use the device mode as its power source. I used a 5V/1A DC regulated charger adapter as a power source. The problem now is that all data becomes erroneous. For example, I expect that the value is 220V, but the gathered data is only at 1V.  I suspect this is a hardware, power supply problem but where could possibly be the error?

I also tried following the suggested reply of Francisco in this thread https://e2e.ti.com/support/microcontrollers/stellaris_arm/f/471/t/322254 by instead having the supply of the Tiva at the +VBUS pins beside SW1, yet it still had the same problem. 

FYI, these are my ADC and UART pin configurations:

Voltage:

VT1 --> PE1

VT2 --> PD0

Current:

CT1 --> PE2

CT2 -->PD1

For TelosB:

UART: PE5 TX, PE4 RX

Digital In --> PE3

Digital Out --> PA6 

Anyone there kind to help? This is an urgent matter. :(

Thanks,

--Lili

  • 0
    Guru 27665 points
    This is rather suspiciously similar

    e2e.ti.com/.../490393

    Same project?

    Robert
  • 0 in reply to Robert Adsett
    Guru 47900 points

    "Suspiciously" to be kind!   But 220VAC - that's a MAJOR Concern!

    Clearly - both posters (thus far) should engage qualified experts - and avoid ALL connections to voltages deemed dangerous.

    A qualified expert may confirm that SAFE grounds are not being properly implemented.

    Such high-voltage IS lethal - only those experienced, qualified & properly licensed should access such potentials...

  • 0 in reply to cb1
    Guru 27665 points
    Good point about the safety, even worse if it's DC. I was thinking the value had to come from an isolated sensor but if not.....

    Robert
  • 0
    Guru 26105 points

    Hi,

    Why do you need an interface with Tiva micro? since the TelosB have 1MB flash memory to log data - I think you need just to instruct it what to do for you - it is what I read from your link provided. ( )

    Edited -

  • 0 in reply to Petrei
    Guru 47900 points

    I'm not so sure your, "Throwing caution to the wind" due to the presence of 2 AA batteries - meets safety requirements!

    Equipment does FAIL - and we are unlikely to know the extent & excellence of each/every protective and/or safety circuit - and 220VAC is - without doubt - LETHAL!   And - do not posters and experimenters (often) "do the unexpected?"  

    Can the presence of 2AA batteries protect everyone - in all circumstances - at all times?   (that appears the thrust of your comment, Petrei)

    I submit that there is ALWAYS - AND SPECTACULARLY - NEED FOR SAFETY!  

    (May I urge you to remove your, "No need for extra "safety" comment - even w/the legal protections afforded humble, "content providers" - which my efforts added to forum boiler-plate (below) - your,  "No need for extra "safety" comment should be deleted!)

  • 0 in reply to Robert Adsett
    Prodigy 40 points
    Yes,

    I added perhaps some imporntant details weren't mentioned.
  • 0 in reply to cb1
    Prodigy 40 points
    Let me clarify, the 220V from an AC source has been stepped down to 12VAC using a transformer. The 12V becomes the input source to the Tiva ADC.
  • 0 in reply to Petrei
    Prodigy 40 points
    Hello Petrei,

    A conditioning circuit is needed for the input signals from my current and voltage sensors (2pairs each for a three-phase circuit using 2-watt meter method). The TelosB mote cannot accommodate all the input signals thus we have to use the Tiva micro to translate analog signals to digital form. From Tiva, data is transmitted using UART serial comms TX/TX to the TelosB.
  • 0 in reply to Lili Andrea Pinero
    Guru 27665 points
    Which must be further conditioned. Also you need to consider what happens if you lose power while still connected to the signal since the signal is both independently powered and likely capable of fairly significant power..

    My comments on the twin thread still stand and are joined by cb1's caveats on working with high voltage.

    Robert
  • 0 in reply to Lili Andrea Pinero
    Guru 47900 points

    Lili Andrea Pinero said:
    Let me clarify, the 220V from an AC source has been stepped down to 12VAC using a transformer.

    May I clarify as well - transformers may (and do) fail - and a primary to secondary short (introducing 220VAC to your Eval board) - may prove deadly!

    I would not "look" into the barrel of a Howitzer artillery piece - likewise - relying upon the manufacturing & handling "soundness" of a (likely) "hobby grade or similar transformer" too often provides, "FALSE" comfort!   Your school - or other directors of your project - may do better to consider low cost DACs - which can effectively generate the desired sinewave - while avoiding (entirely) the danger of line voltage.    (Such DACs may operate at a variety of frequencies - further strengthening their "use proposition!")

    Safety must come ALWAYS first!   All else must follow...