LiPo Powered Stellaris Launchpad

Want mobile power for your Stellaris Launchpad development board? [Philipp] was looking to add some lithium power for the Launchpad. He used an off the shelf single cell LiPo battery and connected it to the 5V rail of the Launchpad board. It didn’t work.

So [Philipp] started looking through the schematics and noticed that the regulator was working fine, but the Stellaris wasn’t starting up. He tracked down a voltage supervisor connected to the Stellaris reset pin. After some investigation, it was clear that this supervisor was holding the device in reset.

The solution is a quick and dirty hack: cut the trace that connects the reset line to the voltage line. With this modification, the device starts up from the LiPo without any issues. [Philipp] does note that you should be careful about battery under-voltage and over-voltage. This hack doesn’t handle charging the LiPo battery, but we’ve discussed that in the past.

Comments

  1. holden says:

    would be a good idea to get a protection pcb for the battery and a usb charger board from sparkfun or make ur own. thats how i have my xbox 360 wireless controller setup with a LiPo battery and i can charge while i use it.

  2. Smoketester says:

    Still waiting for mine to arrive for my opportunity to “outsmart mission control.”

  3. jasonstapels says:

    Might be easier to just get get a two cell LiPo and hook it up with a diode. It seems really odd to me that Ti would have spent the money to verify 5V if it wasn’t needed. Although it might be a simple way to sanity check that the USB isn’t acting up.

  4. fartface says:

    Because designing a proper battery power supply is too much of a bother?

    come on people, the chips are all over the place that do this for you and lets you get a full discharge cycle out of the battery.

  5. fonz says:

    some weird choices TI made, why put the supervisor on 5V input and not on 3.3V which it what really counts, and while they were at it why did they not pick one of the LDOs they have with powergood/reset output

    guess those parts they used where first in like for some advertising

    • cde says:

      Probably because some of the programmer side chips use 5v. The RGB Leds do, the extended boosterpacks do, the In Circuit Debugging Interface does.

      So with this, some if not most new extended boosterpacks won’t work if they don’t arn’t designed to run off low voltages on J3/J4.

      • Philipp says:

        If I didn’t miss something in the datasheet, everything on the launchpad except for the green power led and the RGB led runs of 3.3V, including the debugger interface. +VBUS is only used for USB presence / power detection and maybe some XL boosterpacks which have to be released.
        But of course you’re right, if a boosterpack makes use of +VBUS it propably expects stable 5V and it propably does not work powered by a lipo.

  6. Peter says:

    Lifting the common leg of D2 with a soldering iron would have been a more elegant and more easily reversible solution. Still waiting for mine.

  7. 556NATO says:

    Wow, plug a battery into an EVM, and call it a hack.

    I’m sorry, but this site is getting pretty pathetic…

  8. n0lkk says:

    Sheet the not a hack sentiment rises again. Using the battery wasn’t the hack, cutting the trace to get the combination to work is. In the world in I grew up a hack is lazy- impatient-inexpensive way to get something done, regardless of hazards. The term hack was/is used in a dismissive matter, not in a sense of pride My intention is not to be critical of Philipp, but critical of “not a hack”. Particularly when something fits a long time nearly universal definition of hack.

    • Philipp says:

      yup, I have the same definition of a ‘hack’.
      one might call it not a hack but a mod or just some tinkering, but for me it served a purpose.
      I was unsatisfied that I could not power my brand new, beautiful and cheap dev kit with a lipo, so I started tinkering. I found a solution that works for me and that did cost me nothing. I didn’t bother to design a boost converter / charging circuit to make use of a full battery cycle, because time and money for that would have been way beyond the 4.99$ I paid for the Launchpad.
      The proper charger / booster converter solution from sparkfun is 19.99$ btw ;)

  9. Pietro says:

    I’m not entirely sure about this, but..can i use the +vbus to source energy for some leds using transistors? as the GPIO’s doesen’t have enough current to do so, Or i’ll really have to use some external energy source..?

  10. lmn says:

    What about 2xAA box connected to 3.3V? Should it work?

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