I am using an external power supply but the usb adaptor and power adaptor share a common ground.
I'm using a mac and esp tools to flash it, and it has worked before.
The command I am using is:
sudo ./esptool.py --port /dev/tty.wchusbserial1410 write_flash 0x00000 AT22SDK10020150320boot12.bin
But the response is:
A fatal error occurred: Failed to connect to ESP8266
This make me think something is wrong with receiving data from the ESP because when attempting to connect, the ESPs blue LED flashes.
My usb to serial adaptor works fine though as i've tested it with my arduino.