开云体育

Curious, I still learn new stuff everyday.
I was expecting the REF pin to be high impedance.

I powered up a spare Nano??from 5v with some other project's code it it.
It draws around 17ma while the code boots,
Then after everything is initialized, it goes to 18ma.
We can expect that 18ma to vary by a few ma depending on what code is installed, but not much.

I then shorted the REF pin to ground.
Still 17ma while the code boots.
Then after a couple seconds, current from the 5v supply shoots up to 102ma and stays there.
When I remove the REF pin short to ground, the supply current then falls back to 18ma.

My code uses the ATMega328P's internal 5v rail for reference, just like all the uBitx code does.
I assume what happens is the code turns on an internal transistor switch that shorts the REF pin to 5v.
I have not tried it, but changing this line of code that gets executed during setup()
? ??analogReference(DEFAULT);
to this:
? ??analogReference(EXTERNAL);
should leave that pin in a high impedance state, and I'd expect the supply current on my Nano
to remain at 18ma even with the REF pin shorted to ground.
I may try that later today.

So, a shorted REF cap could go a long ways toward explaining why your Nano is drawing so much current.

But does not explain your 36 ohms from ground to 5V.
I measure over 1.05k on my good raduino with good Nano, and 3.1k on my spare Nano.
Neither changes when I swap my ohmmeter leads.
The Nano reading of 3.1k does not change when I short the REF pin to ground.
And your board is drawing way more than just an extra 84ma.
So you probably have a second problem on that Nano board, not just a shorted REF cap.

The Nano is tough to remove, if it comes to that.
I'd try a little rotary saw or grinder using my Dremel tool for all but the pins hiding
behind the LCD connector, then heat up those few pins on the Nano board to pull it free.
And then extract all the pins one-by-one from the Raduino.
And take care to wash all the metal bits from the Raduino.
If anybody has a better method, perhaps they could speak up.

You clearly know what you are doing, and are on the right track.
Good luck!

Jerry, KE7ER
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