This manual introduces the XLR8 FPGA development board, including function introduction, usage method, difference between XLR8 and Arduino Uno/Sparkfun RedBoard, USB, Xcelerator Blocks, Reconfigurability, I/O, ADC, Bootloader and ICSP header, I2C/Two Wire Interface (TWI), UART, SPI, Analog Compare, EEPROM, Power, Pin13 LED, JTAG Interface, ATmega328p features not implemented, Fuses, Power Reduction and Xcelerator Blocks