1.2 Uno versions

Arduino & Co – Measure, Control, and Hack

Here, note that the pins for the serial port (right) are reversed. The adapter must thus be connected the other way around.

In this example, the serial port pins are also reversed. On the left, adjacent to pins A4 to A7 are a few more pins, but these are already available on the bottom row. MOSI, MISO, and SCK (identical to Pins 11, 12, and 13) can serve as an SPI bus if required. (This is a different kind of serial port, which we’ll discuss on page 256.)

Fig. 1.1d

Fig. 1.1e

For the ATmega328P, there are also larger boards. The best-known is the Uno, and there are many variations of it, such as the original Arduino Uno Rev3 and a plethora of other Uno-compatible boards. Elektor even has its own Uno board, the UNO R4, that, with its ATmega328PB variant of the chip, has additional timers and other features.