Arduinio Pro Mini Issue Fast blinking LED

I have a wireless project so I have two arduino pro minis as a receiver and transmitter. both are powered the same through an AMS1117 5V regulator which is good to 1A going to VCC directly (not vcc raw)

I use the FTDI programmer. one of the arduinos works perfect. The other only works when the programmer is connected. With or without power going to VCC it works fine.

I am testing wow with the blink program.

When I unplug the FTDI programmer, or rather don't have it connected, the LED blinks rapidly (the one on pin 1). It doesn't matter what sketch I upload it does this same thing when powered by VCC only.

For the messed up one, I can upload sketches etc just fine as long as the programmer is connected.

I understand there is an issue here on my part but what does this strange behavior mean? Just stumped because I would think if there is a short it wouldn't work with the programmer installed.

I suggest try:

  1. check that you have a good ground connection.
  2. check for a good ground connection again. :slight_smile:
  3. switch the pro minis so the bad one is powered by the actual power and ground wires which make the properly working pro mini work.
  4. see what happens when you power the bad pro mini through the raw pin.
  5. check the solder joint on the vcc pad/header pin.
  6. check with volt meter to make sure you are getting 5v at the vcc pin.
  7. try the other vcc pin and other ground pin to power your pro mini. The pro mini has 2 vcc pins and 4 ground pins.

It was #1 and #2, I forgot to hook up ground! I had some other stuff connected it must of been getting power from another device.