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newbee alert! questions about MSP-EXP430FR5739


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Ok, at $15, I could not pass... this is my first time playing with microcontrollers.

 

With a coding background, getting the demo recompiled under CCS went smoothly.

After spending a weekend trying to clobber my own code together, I have a few questions:

- I got the code to drive servos working. But, once it runs ( and the 2 servos are powered through the VCC pin on the board and it is in turn powered through the usb cable), the usb connection goes in and out making it very difficult to push new code or debug! Is this due to a lack of power or something else?

 

- To attempt to eliminate the power possibility, I tried to connect a 1C lipo battery to VCC & GND... not good... I nearly lost the magic smoke as the controller got real hot! What jumpers / how can I power this board bypassing the usb power?

 

Thanks!

 

-Fred

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First Don't run the servos off of Vcc

 

this is bad and could cause issues!! you are pulling in way too much current and causing brownouts and possibly overloading the voltage regulator, and funny things may happen

 

the servos should have there own power supply, with only ground connecting all of them together.

 

 

this should solve your power issues

 

as for external voltage with out using usb, you will have to hook up 1.5 to 3vs to Vcc, but double check with the datasheet for that chip. you are very lucky you didnt fry the chip by putting that battery on there

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The VCC is rated at 3.3V. Lipos are 3.7V so you are really lucky that something didn't lose the blue smoke.

 

There is a +5V test point on the MSP-EXP430FR5739 board near the USB port where you can pull voltage from. USB ports are limited to 500mA so you should be ok with 1 servo but for more I would just get a separate voltage supply. I have safely powered one servo this way.

 

The reason the usb connection goes in and out is that the onboard 3.3V regulator is not rated to take the amp draw from those servos so it probably either shuts down automatically or overheats then shuts down.

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