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Wanna PSoC Dev Kit? | Cypress Semiconductor

Wanna PSoC Dev Kit?

Okay, I have one of my favorite PSoC kits (CY8CKIT-030) sitting here on my desk and it can be yours if you are the first to answer these three questions.
 
I have this equation below:
 
f(x) = [x(1/2,414,435)-1]*220     
 
1)      What function is this attempting to approximate?
 
 
2)      What is the significance of “2,414,435”?
 
 
3)      What would be the significance of “726,817”?
 
 

 

First to answer all three will win.  In case of a tie, here is the tie breaking question.

I think Dave is ...............

Fins

Comments

frturan's picture

1) (Possible) error amount for an output x of a 20 bit ADC.

2) Becomes error constant for 20bit ADC

3) Error constant for 19bit ADC

I think Dave is the one needs to be followed attentively.

frturan's picture

1) (Possible) error amount for an output x of a 20bit ADC

2) Becomes error constant for 20 bit ADC

3) Error constant for 19 bit ADC

I think dave is the one needs to be followed attentively.

frturan's picture

(I do not know whether my answers reach you or not, since the wesite does not show a message after submitting.
Therefore I am sending my answer one more time. Sorry if I sent same thing more than once.)

1) (Possible) error amount for an output x of a 20bit ADC

2) Becomes error constant for 20 bit ADC

3) Error constant for 19 bit ADC

I think dave is the one needs to be followed attentively.

hli's picture

1) The function approximates log(x) (the logarithm to base 10).
2) 2,414,435 is ln(10)*2^20 (rounded)
3) 726,817 is ln(2)*2^20 (rounded), meaning that you approximate log2(x) (the logarithm to base 2)
(I admit that I still try to understand how it really works - but KAlgebra and my old school math book helped a lot. I think it work via the identidy between nth-roots and logarithms)

strauch1's picture

Bravo! Give that man a development kit! I've been torturing myself for the last couple of days on this. And here I was pouring over the analog section of the PSoC3/5 TRM looking for clues. The answer was in plain sight. Brilliant!

hli's picture

Here is what I did: first I asked Wolfram Alpha about these number, but there seemed nothing special. Then I took out KAlgebra and drew the graphs (both of them). Then I cross-checked with my math book, and the only candidates for the function where the logarithms. The I tried to see which bases where the right ones for the logarithms, which gave me 10 and 2 (the graphs matched nearly perfect). When I found the identity between logarithm and nth-root, it was simple to find out what these numbers were for. I think the key here was to read Daves clues, and not to assume too much.

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