This is a weird one I haven't been able to figure out.
I'll list out the facts:
- Running 3.3V standalone arduino, uploading sketches via Uno ISP and logic level shifters
- 3 different options for power sources: 3.7 li-ion battery with 3.3V voltage regulator, Uno's 3.3V output pin, or FTDI V out. I typically use the external battery or the Uno's 3.3V one
- Using Sparkfun's USB to FTDI [https://www.sparkfun.com/products/9716 , 5V which I've converted to 3.3V] for serial monitoring for debugging
- Using a 5 year old MSI Laptop GP62 2QD Leopard running windows 10
- Arduino 1.8.12
Now, everything was running fine on my set up. I could upload sketches and succesfully read the serial output from the standalone arduino. The standalone arduino is also functioning as intended i.e. LED's are turning on when they are supposed to and voltage levels look normal.
However, a major Windows update came by a few days ago and I noticed my FTDI voltage output is now at 3.43 volts (up from 3.3V) and is no longer able to read the serial output from the standalone arduino (which is operating at 3.3V). Although oddly enough the FTDI is not able to read the standalone output even if the FTDI is powering it.
I was also getting weird power fluctuations in my mouse: the cursor would move erratically around the screen (i.e. jump around) and have random clicks.
I have solved this problem by removing the webcam and disabling the Realtek USB 2.0 card reader (which according to USBDeview was taking 500mA) and have deduced that something is wrong with the hardware of the laptop.
The FTDI still successfully reads the Uno's serial output (which is running at 5V).
I have a feeling that the Windows updated affected my laptop OR something in the laptop coincidentally broke down.
However at this point I'm not sure what to do. I'm about to open my laptop but any advice on this matter would be appreciated. I'm not sure how exactly to troubleshoot this. I've ordered another FTDI board but it will take a week to arrive.