Comments on AN217

[mikep]

I am posting this as it may useful to other people. I added AN217 to my project with of course a separate thread to do the monitoring (every second). I would rather simply look at the count to determine if the voltage is over or under some threshold.

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Private Const threshold as UnsignedInteger = 514 ' 10V

My suggestion would be to change the readADC() function to return the unsigned integer count. For example purposes you can do the actual voltage calculation in Main as follows:

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Private Const divider_ratio as Single = 7.788 ' discovered from measurement
Debug.Print "Voltage = "; Fmt(  CSng(readADC(PS_Bit)) * (2.56 / 1024.0) * divider_ratio, 3)

Of course now the floating point arthimetric can be simplified to a simple multiply. Multiply is much faster than a divide.

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Private Const ratio as Single = 0.01947 ' pre-calculated constant
Debug.Print "Voltage = "; Fmt(  CSng(readADC(PS_Bit)) * ratio, 2)

3 decimal digits precision is probably too much. I would round to 1 or 2 digits (not shown here).

[stevech]

considered using fixed point in an 16 or 32 bit int?

[mikep]

You may have misunderstood my intent. The original routine contains floating point math. I removed that math from the routine and used it outside only for displaying the output value for humans. For code purposes I suggested returning an integer and then do integer comparisons like this:

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Private Const lowBattery as UnsignedInteger = 520 ' approx 10V (520/52 = 10)

voltage = ReadADC(monitorPin)
If voltage < lowBattery Then
	Debug.Print "Low battery voltage"
End If