vfo.md

VFO USB Knob

The Idea

It was brought up and decided that there should be some facility to accommodate fine tuning the VFO if the user happened to be using a remote rig. Further it was agreed that some sort of USB VFO knob would be the best fit.

The Hardware

I didn't have one of these old-fangled USB rotary USB devices. But what I did have was a junk box.

I've paired a Raspberry Pico with a cheap but decent rotary encoder that has no detents, so smooth rotation. The two together were under 20 bucks.

The encoder can operate between 5-24V, and has 600 pulses per revolution. 4 wires from the encoder are VCC and GND for power, and A+, B+ for pulses.

Even though the Pico is a 3.3v device, the 5v can be pulled from the Pico's VBUS terminal.

So connect the encoder VCC to VBUS, GND to GND, A+ to GPIO22 and B+ to GPIO21.

The Firmware

Load the Pico with CircuitPython. Copy the script below over to the Pico and call it code.py

import rotaryio
import time
from board import *
import digitalio
import usb_cdc

led = digitalio.DigitalInOut(LED)
led.direction = digitalio.Direction.OUTPUT
serial = usb_cdc.console

enc = rotaryio.IncrementalEncoder(GP22, GP21,3)
enc.position = 0
last_position = None
inputstring = ""

def out(data):
    usb_cdc.console.write(data.encode())
    
while True:
    if usb_cdc.console.in_waiting:
     led.value = True
        incomming = usb_cdc.console.read(usb_cdc.console.in_waiting)
        inputstring = inputstring + incomming.decode()
        if inputstring[-1] == "\r":
            if inputstring.strip() == 'f':
                position = enc.position
                out(f"{position}\r\n")
            if inputstring[0] == "F" and len(inputstring.strip().split()) == 2:
                freq = inputstring.strip().split()[1]
                if freq.isdigit():
                    enc.position = int(freq)
            if inputstring.strip() == 'whatareyou':
                out("vfoknob\r\n")
            inputstring = ""
        led.value = False

Misc

I've also included an STL file to 3D print a knob and enclosure and a DXF file for a faceplate.

Located in the usb_vfo_knob folder.