I bought this Arduino clone over eBay. It seems to have an extra SPI and serial ports. How do I use these?

  • Even without extra ports, you can use multiple devices on a single SPI or I2C port anyway by their chip select lines / device addresses respectively. Commented May 5, 2015 at 16:06

2 Answers 2


UNO means ATmega328. It has always only one serial and one I2C port regardless of how many connectors (or solder pads) it is hooked to. They are just parallel outputs to ATmega pins: D0 - TX D1 - RX A5 - SCL A4 - SDA

Extra pads are just for user convenience, for easier wiring.


Those are not additional I2C and UART ports, those are additional connectors connected to the normal peripherals. They are used in exactly the same manner as the normal connector.

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