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