This project has been fun so far, but it’s hard to see the final, working product. I began this journey with the Arduino Nano R3 to be my choice of digital microcontroller. With the Nano, one can create it’s firmware using the Arduino IDE on any computer. The Arduino Nano is very popular, I got 3 of them on Amazon for like $13 with USB cables. I was hooked. I had a little computer that I could program with digital pins I could use to control things for my radio. I had my microcontroller.
I initially had visions of 7 bands, 10m, 15m, 17m, 20m, 40m, 80m, and 160m. I also needed a way to push a button or cycle through a single button to select my band. A computer program, called a sketch for the Arduino, could monitor digital pins that are grounded with a momentary switch. A loop method or cyclic listening function would monitor 7 digital pins and then do something else based on the grounded pin. With the selection of these 7 pins, they are now reserved for this radio operation function or band selection.
The Arduino has analog and digital pins. Some of the analog pins can be made digital but the digital HIGH is labeled floating. Normally the digital pin would be HIGH or 5V but for the analog pin it can drift. The solution is a pull-up resistor and 5V applied. The values are based on pin usage so I’ll not discuss that here. I will however, say that the digital pins are priceless because they can be used as sensors (incoming, grounded, sensing, etc.) or they can be digital representation. The analog pins can be used as sensing too but in an analog way, i.e. they can sense variations from 0 volts to 5 volts.
I have tested a makeshift VFO with a single frequency. I have wired and tested an encoder with this VFO where 4 pins are used on the Arduino that do not interfere with the band select pins. Two pins are currently used to connect with another microcontroller, the Arduino Mega 2560. These pins are serial transmit and serial receive. Two pins are currently used for the I2C protocol. I have tested those with a programmable clock generator chip Si5351a that uses the two pins to send an address and then communicate with that device. The two pins on the Arduino can be an I2C bus if the pins are held high with the right pull-up resistors. I’ve tested continuous frequency memory with each band. I have three dedicated pins for addressing of RF switches.
I also need more pins which I do not have for new features that have not been designed and tested. I ordered a breakout board with the MCP23017 GPIO extender that will give me 16 more digital pins for use with the Arduino. I have not tested it yet. Enter light bulb moment.
Look at this post’s featured image and notice the Arduino Mega, shield and TFT display. Notice the convenience board with screw terminals around three sides. Notice the only two wires. They are serial transmit and receive. You can’t see the ground from the Nano in the photo. Well, you can see that wire crossing over the shield. Only three wires into the complex being. And, notice the little lower life form to the left. You don’t see the momentary select wires into the terminals but all the pins are reserved for something.
Could the Arduino Mega be used for everything and can I use just one complex life form? Yes.
I’ll take an aside on this post to tell you that I’m focused on modular components for my radio. I’ve also made some solid PCBs, i.e. I’m satisfied that they meet my requirements for the proof of concept (POC). But I’m glad that I’ve only done some draft schematics for the controller and display focus.
UPDATE: I’m not going to re-write this posting but I’m now using two Arduino Mega 2560 microcontrollers, one solely for display and the other strictly for control.
My About page provides the background of my project, the Freedom7 HF Transceiver.
If this story resonates, comments are welcome. You can also reach me at david [at] kr4bad-dot-communications. no com
And if you believe understanding matters more than black boxes, you can subscribe to my WordPress https://kr4bad.com/?subscribe=1.
73 KR4BAD David
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