In Arduino 3.0.0 there is a new feature called Peripheral Manager. In the specific case of SPI, when any of its 4 pins (MOSI, MISO, CLK and CS) are used for any other function, for instance, with ...

The DTR pin must be set to high (+5V) -- pin 4 on the DB9. Also RTS pin -- pin 7 on DB9 -- must be tied to ground. DTR and RTS together provide the power to the optical RS-232 interface. Pin 5 on the ...

An Arduino is allowed by the DTR pin to auto-reset when a new Sketch is downloaded. This is a nice feature to have and without having to hit the reset button, it allows a Sketch to be downloaded. The ...