Wrong way to power microcontrolers (i2c project 3,3V & 5V)

Other Hardware General Electronics
6

It's for this project: GitHub - ricaun/DuinoCoinI2C: This project design to mine Duino-Coin using an Esp8266 as a master and Arduino as a slave.

I solved the problem: the FTDI adapter which I tried to use to read the TX pin was not grounded...