Newbie questions about MSP430 & LEDs...

Development Boards MicroMod
1

Hello,

I’m trying to use a MSP430F2012 to operate some LED and a buzzer on a flying helico RC model, which is a quite simple task, but not for a newbie like me…

I have a few questions for which I can’t find answers, even through Google nor reading the MSP430F2012 datasheet and user guide…

  1. The I/O seems to have some pull-up/down resistor (35k) which I guess allow me to connect directly some LEDs without adding resistance ?

  2. If I drive them directly, the current will be driven from the MSP430F2012, and I guess that there is a maximum value, for each I/O and globally, but what are those values ? I don’t want to burn my MSP430 and I couldn’t find any clue on the TI documents…

  3. If the current to light the LED musn’t be driven from the MSP430 I/O, what would be the simpliest (less components) schematic to interface them ?

Thanks in advance for your help!

Have fun.

2

The pull-up/-down option may be used when you configure a Port pin as input. It should not be used when a Port pin is used as output.

As an output, a Port pin can drive/sink up to 6mA. This (as well as other) specification can be found in the data-sheet. The data-sheet and the user’s guide are your primary sources for information. TI also has a lot of code samples, application notes, etc. Seek and thou shall see.

6mA should be enough for most LEDs and you can use a Port pin to drive it with a current limiting resistor in series. TI’s eZ430 target boards all have such a LED at P1.0. They use a 330R to limit the current to about 5mA. If that is not bright enough for you, then you need a bigger/brighter LED and a transistor to drive it.

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Thanks for your help !