Jump to content
kenyee

Turn off Bright Green power LED when running MSP430 Launchpad on Battery?

Recommended Posts

ok...I've dug all over the place w/ Google and had no luck.

 

Is there any simple way to turn off the bright green power LED on the MSP430 Launchpad (1.5 if that matters) when it's not running off USB power?  I'm trying to power it w/ a coin cell battery to see how long it'll run, but that bright green power LED is killing battery life so a CR2032 only lasts 2hrs :-P

 

Share this post


Link to post
Share on other sites

I think if you take the VCC jumper off, it cuts off power from the emulation portion of the board (I seem to remember that this is used to measure current in the getting started labs).  Unfortunately - I believe it also cuts off power from the 3 pin power jumper - you'd have to power the board using the GND/VCC pins from the two 10 pin headers.

Share this post


Link to post
Share on other sites

I think if you take the VCC jumper off, it cuts off power from the emulation portion of the board (I seem to remember that this is used to measure current in the getting started labs).  Unfortunately - I believe it also cuts off power from the 3 pin power jumper - you'd have to power the board using the GND/VCC pins from the two 10 pin headers.

That's not the case. Just did a continuity check on my v1.5 board, with the vcc jumper off at the top. The 3 pin vcc-gnd-gnd still has continuity to the vcc and gnd connections on the 2 ten pin headers.

Share this post


Link to post
Share on other sites

What's weird is my code (programmed into the MSP430) doesn't seem to run if I pull the VCC jumper off (my code blinks the programmable green LED on startup).

CR2032 is wired into 3 pin vcc/gnd/gnd connector.  If I put the VCC jumper on, the bright green power LED lights up and the programmable green LED blinks...

Share this post


Link to post
Share on other sites

Bingo!  :-)

Specifically, the reset jumper.  I put the test jumper back in w/o problems.  Weird.

 

ok, so for battery use, connect it to the vcc/gnd/gnd (only one gnd has to be connected to the battery).

Pull off the vcc/reset jumpers in the block of jumpers in the emulation section.

 

It's now running happily off a cr2032...

Share this post


Link to post
Share on other sites

@kenyee - will you report back how long you manage to get it to last? Also, whats your application doing? Is it an on-all-the-time style Arduino/Energia application or does it sleep and wake?

 

The solution is a simple hardware one: remove the Vcc and reset jumpers. 

 

The LED is a USB power indicator.  Powering via the (3V3) 3-pin header on the opposite corner from the USB connector will bypass the USB power.  However, unless you remove the reset and Vcc jumpers, the battery power will be used to power the (unneeded) programming side of the LaunchPad, including the power LED.

Share this post


Link to post
Share on other sites

@kenyee - will you report back how long you manage to get it to last? Also, whats your application doing? Is it an on-all-the-time style Arduino/Energia application or does it sleep and wake?

 

It lasted roughly 1 month (I was hoping to get at least 3) and goes into deep sleep after a few minutes (blinks an LED when it's awake and that uses more power than the wake mode)-:.  It's a sleep and wake app...that's really the only way you'll be able to get decent battery life out of the MSP430.  The MSP430 uses more juice than some other microcontrollers while running at full speed, but it sleeps deeper.

Share this post


Link to post
Share on other sites

And it sleeps more shallow if needed without sacrificing all features.

I think that is one of the main reasons for TI to move so much stud away from the core, so that it might stay awake if required.

LEDs are very power hungry, alas.

Share this post


Link to post
Share on other sites

The solution is a simple hardware one: remove the Vcc and reset jumpers. 

 

The LED is a USB power indicator.  Powering via the (3V3) 3-pin header on the opposite corner from the USB connector will bypass the USB power.  However, unless you remove the reset and Vcc jumpers, the battery power will be used to power the (unneeded) programming side of the LaunchPad, including the power LED.

Wish I'd remembered this thread when I was testing the LiPo boosterpack this weekend.  Leaving on the RST jumper doesn't seem power the emulation side of the board (at least the LED doesn't turn on) - but it does keep the MCU in reset.  Voltage on the reset pin is something like ~1.4v instead of 3.6 that I get when I pull the RST jumper.  I did a check on the resistance - and the resistance is lower when the jumper is on.  I'd have to take a look at the schematic more to figure out exactly what's up.  Thought I was going crazy until I realized I had to pull the extra jumper.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...