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The Raduino is a DDS VFO based on the Silicon Labs 5351A DDS Chip, an Arduino Nano Module, and a parallel LCD display.

The Si5351A is controlled by the Nano via an I2C bus and provides three clock outputs, one of which is currently used. The Wire.h library handles the low level I2C bus commands and the si5351.h library handles the low level interface to the DDS chip.

The LCD Display is a common parallel interface LCD module used in 4 bit mode to conserve I/O pins at the cost of two transfers per character. These modules typically use the Hitachi HD44780 display controller and command set. The LiquidCrystal.h library handles the low level interface to the LCD module.

The Arduino Nano with the Raduino.ino sketch(aka program) turns all of these parts into a DDS VFO. The Nano is based on the AVR ATmega328 8-bit processor running at 16 MHz. The Nano has 32KB Flash, 2KB SRAM, and 1KB EEPROM memory. Nano I/O consists of 14 digital pins and 8 analog pins. Note that Arduino I/O pin numbers are an abstraction and don't correspond to chip or module pin numbers.

Two headers provide access to the various DDS VFO signals. The 16 pin "Oscillators" header provides access to the three clock outputs and Nano digital I/O pins D2-D7. The 8 pin "Controls" header provides access to Nano analog pins A0-A3 and A6-A7(A4(SDA) and A5(SCL) support the I2C bus and are not brought out on either header). Note: Analog pins, except A6 and A7, may also be used as digital I/O pins.

The Nano pin assignments are as follows:

     1    D1/TX/USB             USB Interface to PC, Downloading and Serial Comms
     2    D0/RX/USB             USB Interface to PC, Downloading and Serial Comms
     3    RESET
     4    GND
     5    D2           OC6        External Interrupt Pin - Spare(?)
     6    D3           OC5        External Interrupt Pin - Spare(?)
     7    D4           OC4        TX_LPF_SEL
     8    D5           OC3        CW Key(future)
     9    D6           OC2        CW Tone(future)
    10    D7           OC1       TX/RX(future)
    11    D8           LCD4      LCD RS - Parallel LCD Module in 4-bit mode
    12    D9           LCD6      LCD R/W
    13    D10         LCD11    LCD D7
    14    D11         LCD12    LCD D6
    15    D12          LCD13    LCD D5
    16    D13          LCD14    LCD D4
    17    3V3
    18    AREF
    19    A0           CC8        Spare(?)
    20    A1           CC7        Analog Keyer(future)
    21    A2           CC6        Calibrate Push Button - Digital w/pullup
    22    A3           CC5        Function Push Button  - Digital w/pullup
    23    A4/SDA    SI5        Si5351A I2C SDA
    24    A5/SCL    SI4        Si5351A I2C SCL
    25    A6           CC2       PTT(future)           - Digital w/pullup
    26    A7           CC1       Tuning Pot Wiper      - Analog
    27    +5V
    28    RESET
    29    GND
    30    Vin

    OC  - Oscillators Connector
    CC  - Controls Connector
    LCD - LCD Connector
    SI  - Si5351A Pins