One of my first board designs also happens to be one of only a hand full I designed in Fritzing.
Tag: Arduino Uno
Atmega328 Bootloader For GRBL
While brainstorming ideas the other night. I found a few threads online saying how the default behavior of Optiboot to flash the led residing on Arduino pin D13 could cause things to act randomly when using this pin as a output to control something like a relay.