LM373 ~ Arduino & Si5351

The use of the Arduino and the Si5351 can cause hair pulling, fallen arches and a bad case of dandruff! The problems typically encountered can be traced to the builder and not the code or the hardware. So beware and follow closely what is being shared and this shouild result few if any problems.

The Arduino essentially provides the control and traffic direction for operating the Si5351 PLL Clock Generator and the 160X128 Color TFT. But it is not just a simple matter of connecting a few wires and you are done, as there must be much in the way of preparatroy work that must be accomplished first. If taking that path conflicts with an individual's slash and burn attitude, then you best build an archaic analog VFO and BFO. So if you want to go modern here is a check list of things you will need just to start the process.


1 Arduino Nano
You can use a Uno R3 or Pro-Mini. But the Uno is a much larger footprint and the Pro-Mini lacks a 3.3 Volt Regulator which you will need for the display. I have used a Pro-Mini but added an external 3.3 VDC Regulator. by and large the Nano is the best choice.
Adafruit Si5351 PLL Clock Generator
Be sure to order the SMA connectors for the board. Don't skimp --get the connectors.
2 Foot RG-174/U Coax cable with a male SMA at each end.
This cable can be purchased from Jameco Eelectronics. Cut the cable in half and you will have two 12 inch long cables with a male SMA at each end the the wire end is soldered to the circuit board
Circuit Board
Purchase a prototype circuit board with plated through holes. The size should be about 2.5 inches by 1.5 inches. There is enough room on the board to install the Nano, the Si5351 and a 9 VDC @ 1 amp regulator. I use pin headers (two rows along each side of the Nano) and then connect each Arduino pin to the header pins.
Jumper Wire Pack with a Female to Female at each end. Get the 8 inch long ones.
Using the jumper cables enables going from the header along each side of the Nano to the display -- all that is involved is a simple plug into the Arduino header on one end and the header on the display. There are 7 wires for the display. For the encoder I plug into 4 pins on the header and then cut the other end of the cable so that the four wires are then soldered to the encoder. The same process applies to the two switches (USB/LSB Select and Tune). An additional cable is plugged into Pin D6 and that is the output from the Tone Pin used on tune up. The other end of this cable is soldered to the RC filter.
I use a mechanical encoder from Bourns and available from Digi-Key. These cost about $1.50 and are good for 100K rotations. They have no detents and provide a smooth transition. The Step Tuning Rate Push Button is integral with this encoder.
Color TFT
The unit chosen is the 160X128 as this provides just the right size of viewing area and has four "real mounting holes. The 128 X 128 is smaller and not easily mounted to the front panel. Avoid using the Nokia Black and White display model 5110 as well as the OLED. The problem with the OLED is that you must add a measure of sheilding and bypassing to avoid "oled noise" from being heard in the receiver.
You will need libraries for the Display and the Graphics package. Both can be downloaded from Adafruit. Note the sketch was developed using Arduino IDE 1.0.5 (an oldie) You will also need files for the rotary encoder and the Si5351. I will include these files as a link with this page.
9 VDC Regulator
The power supply for the Nano is derived from a 9 VDC TO-220 style regulator mounted on the circuit board.
Aluminum pillars, molex connectors (4 pin and 2 Pin), nuts, bolts, 15 pin headers (two each). multicolor wire.


Arduino Pin Assignments


The several files provided below are in a Notepad Text format. Copy and paste each file into an Aruino IDE save the 5 files in the same project folder in your Arduino Directory. If you have questions at this point about how to do this--don't build the project ! You must also have in your Arduino Library folder (part of the Arduino Directory) the necessary libraries to run the 160X128 Color TFT. These are both (GFX and 7735) available from the Adafruit Industries website. If you have questions about how to do this --don't build this project.



Special Note about the TUNE function. To engage the TUNE function simply switch the MOX button (a panel mounted switch in parallel with the PTT) and then hit the TUNE momentary Push Button. For about 10 seconds a pulsed 988 Hz tone is fed into the SBL-1 Balanced Modulator. Don't skip adding the RC Filter as this takes the 50% duty cycle square wave from the Arduino and makes it look closer to a sine wave. When the timing cycle is over, disengage the MOX switch and the rig is returned to receive.

The MOX button is a throw back to the old days of early SSB Transceivers; but I find it nice to be able to turn on the transmitter without having to hold down the push to talk switch. This was esepcially useful during the early stages of aligning the transceiver. But undoubtedly this approach will be the butt of jokes and comments on the illuminati reflectors.

So if you do not want the panel mounted MOX toggle switch, built into the code is a way to do it so when you hit the momentary Tune Push Button, the rig will automatically go into the Transmit mode. Pin 7 on the Arduino is identified as the LED in the code and will go "HIGH" upon engaging the TUNE routine.

Already existing is the DC switch which toggles the PTT relay. When the Solid State Switch is transitioned to Transmit and Supllies 11 VDC to various parts of the citcuit that also supplies "juice" the the PTT relay by closing a transistor switch connected to this relay.

A connection is made from 11 VDC "T" to a 10K, 1/4 watt resitor and the other end of the resistor is connected to the base of a 2N3904 transistor. The Collector is connected to the relay terminal (Bottom End) and the Emitter to Ground. Power for the 2N3904 comes through the TR relay coil. The 11 VDC VDC on the Base is the switch trigger.

A second complete transitor switch circuit can be connected in parallel to the Microphone PPT that is now triggered by 5 volts from Pin 7 on the Arduino. On TUNE the second transistor switch will close the relay and no need for the MOX switch. So OK you just had to look at the Arduino Pin Assignments and you will indeed see "Hot Pin on Tune" for D7! I guess I am now square with the illuminati reflectors. Or you could leave the MOX switch and it is only used for manually turning on the transmitter circuits.