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MSP430FR6989: Infinite power?

Michal Jazwinski
Prodigy 40 points
Part Number: MSP430FR6989
Other Parts Discussed in Thread: MSP-EXP430FR6989, , ENERGYTRACE, MSP-FET

Hi,

I wrote a simple code to read analog value and show the value of the voltage on the attached LCD. Mainly I modificied OutOfTheBox programm. My goal was to provide the lowest energy consumpition I can get based on my current knowledge (it's my very first own piece of the code).

The program is running and everything seems to be ok, so after measuring energy consumpiton with Launchapad powered through eZ-FET (Rev1.2) I decided to remove 3v3 jumper from isolation jumper block (J101). But, what suprised me, after I put USB cable back to my PC Launchpad is still working.

My currently jumper block connections looks like that:

5V, 3v3, RTS, CTS jumpers removed

All the rest jumpers are on the place.

So, am I doing something wrong or my Launchpad is damaged? I just want to measure current energy consumption with external energy source.

I attached my code.

I'm using MSP-EXP430FR6989 Launchapad.

Thank's in advance!ADC_LCD_rev1.zip

Thank's in advance!

  • 0
    TI__Mastermind 49692 points

    Hello,

    Thank you for your detailed post.

    I suspect that the MSP430FR6989 is getting back-powered through the pins connected to populated jumpers across the isolation jumper block. It's recommended that the MSP430 is powered up via VCC before applying signals. If not, unknown behavior or even damage to the device can occur.

    For accurate energy consumption measurement, I would suggest using our EnergyTrace feature in CCS, which is supported by the on-board eZ-FET emulator. What I'll do is populate all the jumpers across the jumper block, plug in the LaunchPad to the PC, program the MSP430FR6989, halt the debug session, unplug the LaunchPad, remove all the jumpers except 3v3 and GND and any other jumpers on the board (for LEDs, etc.), plug the LaunchPad back into the PC, and start EnergyTrace in CCS.

    Also, the ULP (ultra-low power) tool is integrated into CCS. It offers advice on how to reduce power consumption, so the resources below should be helpful.

    Hopefully this helps.

    Regards,

    James

    MSP Customer Applications

  • 0 in reply to James Evans
    Prodigy 40 points
    Thank's for the answer it was very helpfull.
    Just one more question, what if I want to power up my Launchapad through externall source of enerrgy (ex. battery) and measure power consumption with eZ-FET and EnergyTrance?
    So far I get GND, SBW RST and SBW TST jumpers populated and battery connected to pin 1 on J1 header. The Launchpad is powering up properly but EnergyTrance shows zero in basically all fields.
    Sorry for dummy questions.
  • 0 in reply to Michal Jazwinski
    TI__Mastermind 49692 points
    Hello Michal,

    If you do use EnergyTrace, you'll only want the 3V3 and GND jumpers populated.

    EnergyTrace is the most accurate method for measuring the power consumption, since it can measure the currents during different LPMx modes very quickly. Basically, the debugger (e.g. eZ-FET, MSP-FET) measures the voltage drop across a dedicated low-resistance resistor as the current supplied to the 3V3 pin flows through it. Thus, EnergyTrace cannot be used with an external power source like a battery.

    Another common method is connecting a multimeter in series with the battery and the load, but this tends to show the average current, which ultimately depends on the LPMx modes in the code. Another, better alternative to the multimeter would be a DC power analyzer. This way, you could provide the exact supply voltage as your battery would supply and with the observed current consumption, you could calculate how long the battery would last.

    What's the type and output voltage of your battery?

    Regards,

    James

    MSP Customer Applications

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