Can't receive serial data from Arduino

Hi everyone, I’ve been working on data logging a project with Arduino, and so far it was working ok, except for some variations on the ADC readings… Anyways, I was able to receive data measured by the arduino on the serial monitor without trouble, but now when I connect it it won’t send any data.

  1. The Tx light doesn’t blink.

  2. I thought it could be the RTC I’m using, so I made the arduino show me the time (this was the solution I used before and it was just a time reset), but it doesn’t show a thing!

  3. I’ve measured 5.1 V from my USB port, and the Arduino 5V output gives around 4.6V

  4. I’ve tried with two different Arduino UNO R3 boards, and both behave the same.

I really would appreciate any thoughts on this, thank you all!

Fixed it! It seems like the RTC wasn't connected as it should be. =D