T 20 Digital input / output ports:TX, RX, D2 ~ D13, A0~A5 8 analog inputs ports:A0 ~ A7 1 pairs of TTL level serial transceiver ports RX / TX 6 PWM ports: D3, D5, D6, D9, D10, D11 Main ChipAtmel Atmega328P-AU Support Serial Download Support external power supply 3.8-12V DC Support 12V or less than 12V battery power supply 16MHz clock frequency Size: 33.8mm x 18mm