An Arduino Si5351a quadrature VFO controller

https://github.com/nick6502/Si5351a_quad

I’ve decided to start keeping my files on github.com because updating and maintaining posts on dreamhost using WordPress is just too complicated for me.

But isn’t github also complicated?  Yes, it is. But if you just want to download the files, it’s easy. Just go to that green button that says “Code” and click the drop-down at the right and then select “download zip file”.  You’ll get a zip with all the source code, the manual, schematics and whatever.

Hey, when I inserted the github link, my entire post disappeared! I guess that validates what I was saying. No matter because there’s a complete manual in the github file package.

But I’m going to cross my fingers and see if I can paste in an overview from the manual:

This document describes my Arduino Si5351a controller program for the Arduino.

Features include:

• A keyed line input, so the controller can swap between TX and RX frequency outputs as required as the user keys and un-keys the transmitter.
• A TX_Out output pin echoes the keyed line input, but doesn’t change state until the TX frequency registers have been sent, and changes back to key up before the RX frequency registers are sent.
• An LCD display to show the frequency I’m on, menu options and so on.
• A user settable CW Pitch value which is the amount that the VFO shifts between TX and RX states if in CW mode.
• CW/Phone mode selection which functions to enable or disable the CW offset shift when the key line is closed.
• LSB/USB selection. This chooses the direction of CW offset in CW mode, so the user can listen to a station on either side of zero beat. In CW it’s sometimes called NORMAL and REVERSE operation. There is also an output pin SB_Relay than cab be used control a sideband select relay in the receiver. Also, the phase difference between the outputs alternates between 90° and 270° when this selection is made.
• RIT control. This provides for separate TX and RX frequencies, with both displayed. The receiver can be tuned without disturbing the transmit frequency. RX and TX frequencies can be swapped and the offset can be zeroed without turning off RIT.
• Frequency step selection. There are both a menu for selecting from seven step sizes and a quick pushbutton selected step change between fine (10 Hz), medium (100 Hz) and fast (1 kHz).
• Band selection with all ham bands from 3.5 to 144 MHz selectable, but unwanted bands can be omitted from the sequence.
• A Save State menu option which writes most of the current parameters into EEPROM so the VFO will start in the same state the next time it is powered on.
• Three miniature pushbuttons allow quick selection of often used functions while a menu controlled by the rotary encoder is used to access other functions. The pushbuttons operate with the familiar TAP and HOLD logic, giving two uses for each.
• A sidetone which sounds when the key is closed. A menu option can enable or defeat this function.
• An option for superhet operation with an I.F. (intermediate frequency) offset added to the displayed frequency when in receive mode.
• A separate transmit output on clock 2 may be specified. It is keyed via key or PTT input.
• A simple VFO mode where output is ON when the key is down and OFF otherwise, for driving simple transmitters.
• The ability to control a PCF8575 IC which has 16 output lines and can select relays on a per-band basis. For example, to select low-pass filters in a transmitter.