Hello friends! Today we will install the Arduino bootloader on an ATmega328P using a second Arduino Uno as the programmer. This is useful when replacing the socketed processor on a classic Uno or restoring a compatible target whose serial bootloader has been erased. We will follow the original two-board arrangement: board B is the working programmer, and board A contains the target processor. Giving the boards separate roles helps prevent a common mistake, which is changing settings for one board while accidentally programming the other. The title uses the familiar ATmega328 family name, but the standard classic Uno configuration targets the ATmega328P. Read the marking on your chip before starting. An ATmega328, ATmega328P and ATmega328PB are different device selections; a similar name is ...