processor and memory
● Atmel 32-bit microcontroller
● Speed: 48MHz, ARM7
● Code Storage: 152 KB
● RAM: 64 KB
digital i/o features
● all 16 digital and analog pins: GPIO
● pins 1-3: RS232 TX, RX, DTR
● pins 9-10: I2C SDA, SCL
● pins 11-12: UART 1 TX, RX
● pins 14-16: SPI MOSI, MISO, SPCK
● pins 17-20: PWM, PWM, PWM, PWM
power pins
● pin 4: GROUND
● pin 21: 5 VDC regulated (input/output)
● pin 22: /RESET
● pin 23: GROUND
● pin 24: 7.5 - 12.0 VDC (input)