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Date: Wed, 30 Oct 2024 16:32:02 -0400
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On 10/30/2024 4:07 PM, john larkin wrote:
> Things I've seen, and even done, in Spice sims...
> 
> Bypassing voltage sources  (not me!)
> 
> Worrying about resistor power dissipation
> 
> Using standard parts values, like 4.7K ohms or 33nF, when the control
> loop will be mostly code anyhow
> 
> Using +-12 or some such opamp supply voltages, and scaling signal
> levels to fit. The LT Spice universal opamps will work with hundreds,
> or thousands, of volt supplies.
> 
> Drawing hideously ugly schematics without a title, author, date, or
> named nodes.
> 
> 
> So I'm rescaling a power supply sim (I'm waiting for a run to finish
> now) to have everything in actual 1:1 units. Then we will write the
> control loop code to work in those same real engineering units, not
> some goofy scaled integers or anything like that.
> 
> Keeping everything in true units as floats is ideal, but the RP2040
> floating point ops are kinda slow, so we may express things as 32-bit
> values, 16 bits of signed integer and 16 bits of fraction, as a sort
> of fast and cheap float. But 12.5 volts is still visibly 12.5,  just
> as if it were a float. That will be handy for debugging.
> 
> S16.16 is plenty good to express voltages and currents in a power
> supply.
> 


Floating point sucks for low frequency systems with relatively long time 
constants, anyway