Basic Arduino VFO for crystal replacement

VK3ZYZ

Moderator
This will be the next version of my basic Arduino VFO to replace crystals in old sets.
The board size is a little over 2" a side.

NanoVFO_20200818.png
It is a pretty minimum system, but does include CTCSS. The encoder and display are not mounted on the board and all interconnects are with wires soldered on. No connectors, unless you want to use the Si5351 board COAXs for the VFO outputs.
NanoVFO_cct_20200818.png

I intend to get a batch of these made.
Any comments appreciated.
 
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VK3YNV

Moderator
Hi Denys,

Thats almost exactly what I need for the FM 828 conversion, any chance you could fit a 5V regulator on there?

I'm not sure what supply rails are available in the 828, and I could just put a recom 5V 0.5A regualtor in a corner somewhere.

Put me down for at least 3.
 

VK3ZYZ

Moderator
I was thinking of a 5V reg too. The nano reg may be enough, but a 7805 is probably a good idea.
I'm about to have a try...
NanoVFO_20200818_reg.png

Here is the updated board design. The 5V external reg will mount under the board.
If it is not used, a link needs to be installed.
NanoVFO_cct_20200818_reg.png
 
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VK3YNV

Moderator
I should have checked the nano cct, they are using a 78M05 which should be good for up to 35V max and 500 mA So probably the only good reason to have a regulator external would be to remove some heat from the nano. Does the 78M05 get hot running off 12V?

How much current does the OLED and Si5351 draw?

Nano cct attached.
 

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VK3ZYZ

Moderator
I have not measured the current. It will be higher if an LCD is used as the back light will need more current.

Finally, after a bit of a problem with the files, 100 boards are on order :)
Look here in a couple of weeks if you want a board or boards.
 

VK3YNV

Moderator
Good news! What did you find out about the files not displaying on JLC?

Put me down for 10, I've thought of a couple of other projects I can use them on. :)
 

VK3ZYZ

Moderator
I think a couple of the layers I had selected were empty. That mucked it up somehow.
Not really sure.
I wonder if I should order the main parts and provide kits?
 

VK3ZYZ

Moderator
They look like "real" encoders. Not the toy ones I have.
But there is a bit of a cost difference!
But I have a couple off these...
Encoder-600P R.jpg
When testing them, I found more than 5V was needed. They are OC outputs, and quite a bit bigger that the toy ones.
Not too bad for around $20.
 

VK3ZYZ

Moderator
Just because I wanted to see if I could, here it is running on an STM32F103 board. This has taken me many days, even with starting with working Arduino code!!!
My son helped me with a syntax problem as I could not figure out how to write to a port, as distinct to a pin.

GPIOA->regs->ODR = 16 ; // This writes the value of 16 to the port A. Obvious ?????????

I've done some kludges, but they seem to be working. Note that I have not tested it with the Si5351 board as I'm waiting for them to arrive.
STM32F103 Development board.jpg
STM32F103_Subtone.jpg

I may do yet another PCB to suit the STM32. As they have a lot more memory than the Arduino, not to mention running at 72Mhs in stead of 16Mhz, more features, like a meter, may fit.

There is of course the possibility that 72Mhz x 2 = 144Mhz. I wonder what that could do?

Here is the code as set up for the Trio 2M set if you are interested.
With some tweeks, this will suit other radios.

EDIT: Added a delay at startup as the OLED display did not wake up on power up.
 

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BillC

Active member
HI Denys i am watching with interest. Your Vfo would suit one of my receiver projects. I have a Telrad 9 meg filter/demod board . The Si5351 would provide the three outputs required. clk 0, 0-31 meg vfo , clk1, 36 meg clk 2, 9 meg. In the mean time i am building a 9 meg. xtal . oscillator and multiplier to 36 megs. The Telrad board has a down mixer (1496 ) there are upper and lower sideband filters with sideband offset in each case , and each of the filters has its own 1496 product detector so 9 megs for the product detectors and 36 megs for the down mixer , 300 millivolts injection to the mixer and product detectors . The first IF is 45 megs . Cheers $%# .
 

VK3ZYZ

Moderator
Hi Bill.
Yes, it sounds like it will work ok.
On the Codan VFO, the Si5351 does generate 3 different frequencies.

I've just made a mod to my development board. There is now another socket for a second I2C display, and the on board one has the address select extended to a PCB switch so I can easily change the address.
Also, the Boot0 link on the STM32 board has a switch instead to the link.
STM32DevelopmentBoadsMods1.jpg
One trap is that the various I2C displays do not all have the same connections. That needs to be checked before a display is plugged in.
 
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VK3ZYZ

Moderator
I could not sleep as ideas were swirling around in my head. So I got up again and had a play.
Here it is with the second OLED display as an "S" meter on receive...
STM32_VFO_RX.jpg

and as a power meter on transmit...
STM32_VFO_TX.jpg
Note the ruler (with a coffee mug for weight out of the picture) pushing the PTT switch down as I ran out of hands!

There is a movie of it in action too.
Also, the code so far. That is more as a backup for me than anything, but is anyone wants a look, you are welcome to it.
The meters are not being fed with any signals as yet, and one problem I have to work out is how to write to just PA0-PA5 without disturbing PA6 and PA7 as I want to use them as analog inputs.

Now, maybe I can sleep ;)
 

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VK3ZYZ

Moderator
It looks to be working, at least as far as I have tested it. The Si5315 is missing as I don't think i have a spare not soldered down. More are due, so I will wait.
This test has a 2-x4 LCD just because it was what was on hand, and the address had to be changed to 0x27, and the lcd.begin to (20,4).
On the up side, it allows me to play with the test placement a bit more using the lcd.setCoursor(0,3) to start the text on the 4th line. (line numbers start at 0).
BasicVFO_running.jpg

I think I got her R2R resistors wrong as it looks like I am missing at least one bit. The R2R network may work correctly, I hope.
EDIT: Yes it does. The picture below is with crook resistors. I'll have to update it later...
BasicVFO_R2R-resistors.jpg
But with a bit of filtering, this will work ok as it is. At least the frequency is correct :)
 
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