GH327 Interface Board Reference Manual
The GH327 Interface Board provides either a stand-alone FM RDS application device, or an interfacing bridge to other devices via either a UART interface, or an XBee ZigBee RF module. The board uses an 8-bit AVR MCU to control all the interfaces, including the FM board. The MCU can be reprogrammed via an ISP header on the board. The GH327 Interface Board also contains a RS232 transceiver converting the UART interface into a PC compatible RS232 port. Lastly, the board should be powered by a 5V source of at least 100mA.
Component Descriptions
MCU: ATMega644
The ATMega644 is a general purpose MCU with a rich set of peripherals built in. The processor is clocked with an external 8MHZ crystal, but a value of up to 10MHZ can be used. The MCU features a built-in Flash and EEPROM memories. The flash is used to store code which can be reprogrammed via the ISP header on the board. The EEPROM memory can be used by the application programmed into the chip, one such application is to provide a unique ID to each board as no unique hardware ID exists on the board.
The ATMega644 is the heart of the board, it interfaces to the FM RDS chip, as well as the UART bus. The MCU makes use of the UART bus by a built in UART peripheral. The UART bus can be used in two ways, either to interface to the XBee ZigBee radio, or to interface to an RS232 port through an RS232 transceiver. The UART peripheral can be programmed via either interrupts, or polling. The interface to the FM RDS chip is realized with the use of an I2C peripheral also built into the ATMega644. The bus is pulled up sufficiently via resistors to allow for the maximum 400Khz communication speed. Like the UART peripheral, the I2C can be programmed using interrupts or polling as well. Please refer to the ATMega644 datasheet for more information on these peripherals, and others.
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