Caio Santos

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7 years ago.

Problem with External Power Supply in FRDM K64F

So I am using a FRDM K64F and a LCD 16X2 to control some Optical Amplifiers. During the test phase I would power everything with an external power supply of 5V and 2A and used an USB on my controller to Debug and such. Everything was working fine and I finished the project so there was no need to keep on using the USB. So I removed the USB and to my surprise, the LCD doesn't work. The following happens:

  1. If I power everything without USB, the LCD just stays blank;
  2. If I power everythign with the USB connected it works fine;
  3. If I power with USB and remove the USB afterwards, it works fine;
  4. If I power without USB it doesnt work, but if I plug the USB afterwards it starts working.

I think it might be a problem with the external power supply, but 5V and 2A is more than enough for the application. I am powering the board using the Vin pin. All grounds are connected.

Anyone have an idea to why this happens? Thank you for your time.

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