Tuesday, May 19, 2020

An updated version of my VFO-BFO

A couple of the projects I have been working on have been put on hold because of the shipping delays caused by the Covid shutdown in many places.  Looking around for something that only required what I knew I have on hand.   I rembered seeing a YouTube video of a SI5351 based VFO with a small TFT display that very nicely simulated a mechanical dial.  Going back I found the video, and there was a link to the website of JF3HZB, the schematic , and Arduino code for the project.  It uses the same 128 x 160 TFT display I have in my VFO-BFO, and a ESP-32 dev. board.  Looking at what pins are required, the small Wemos Mini I have should work nicely.
I downloaded the software, and got  it to compile without any problem. After looking at the code, I can see where having two 240 Mhz. cores doing the processing is nearly a necesity for something like this.  And also still has plenty of  room and power to addd other features.  I quickly built a simple board to see how it looks, and works . 
After getting the basic software running for the display, I did some modifications to add a couple things I want to have on the display. a LSB/USB indicator and I will probably add a T/R indiator light of some type.  The response of the display is really nice, except for some small jumping around that is coming from the really cheap rotary encoder I used.  I have  a couple better ones that I will use after I get a board designed, now I will see if I can correct with some filtering capacitors.

I plan on using one of the Adafruit SI5351 modules I have, so will have to see what if any changes I have to make to use them with 3.3 volt logic instead of 5 volt.  I have not looked at the 5351 library used with the original  software, so do not know if I will keep it or use the same library I have used before.

Trying to think about what I want to include on the board design. All the pins required are on the inside set of pins on the Wemos module. That means I can just add some header pins to the top of the Wemos module instead of having to route them  on the board. This should allow for fairly easy expansion. 

I like the single analog pin method for monitoring multiple push buttons.  I will probably add the resistor chain and some header pins on the board to make it easy to add several push button controls.  Also thinking of having provision to add a retoary encoder directly on the board, or  a connector for adding an external encoder.
 I will get started on the board layout, then decide if I want to order some from one of the board houses.  They all offer DHL shipping, so should not have to wait too long to get them.

I tried to make a video of the board working, but couldn't find a way to keep the camera steady while operating the encoder.
So here is a link to the original YouTubevideo I watched.

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