Fixed point coder log10 implementation

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Jogger
Jogger on 19 Nov 2020
Answered: Jogger on 26 Dec 2020
I am using 20*log10(val) to get power in a dB
y = 20*log10(3)
But When i am using matlab coder to convert the in c/c++ code.I am gettig an error
Function 'log10' is not defined for values of class 'embedded.fi'.
Can someone help me with alternate way of doing dB calculation.
Thank you

Accepted Answer

Jogger
Jogger on 26 Dec 2020
qsb = fixed.Quantizer(numerictype(1,32,24));
y0 = quantize(qsb,20*fi(log(double(x)),1,32,24)/fi(log(double(10)),1,32,24)); % log(x)/log(10) for log base 10 i.e. log10
y1 = 20*log10(x);

More Answers (2)

Darshan Ramakant Bhat
Darshan Ramakant Bhat on 19 Nov 2020
The function "log10" is supported for code generation in the latest version (R2020b) of MATLAB. You can find the list of supported functions in the below page :
  1 Comment
Jogger
Jogger on 19 Nov 2020
Thanks - I see, is there a way I can use with R2019b ?

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Jogger
Jogger on 20 Nov 2020
I made a test and I don't see the expected result
I am still getting the error following error
??? Function 'log10' is not defined for values of class 'embedded.fi'.
My question - did you verify log10 ?
Below is the matlab version
>> ver
-----------------------------------------------------------------------------------------------------
MATLAB Version: 9.9.0.1524771 (R2020b) Update 2
MATLAB License Number: 40523231
Operating System: Microsoft Windows 10 Enterprise Version 10.0 (Build 18363)
Java Version: Java 1.8.0_202-b08 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode
-----------------------------------------------------------------------------------------------------
MATLAB Version 9.9 (R2020b)
Fixed-Point Designer Version 7.1 (R2020b)
HDL Coder Version 3.17 (R2020b)
HDL Verifier Version 6.2 (R2020b)
MATLAB Coder Version 5.1 (R2020b)
Parallel Computing Toolbox Version 7.3 (R2020b)
  6 Comments
Jogger
Jogger on 21 Nov 2020
I found the right implementation -
qsb = fixed.Quantizer(numerictype(1,32,24));
y0 = quantize(qsb,20*fi(log(double(x)),1,32,24)/fi(log(double(10)),1,32,24)); % log(x)/log(10) for log base 10 i.e. log10
y1 = 20*log10(x);
Question - Matlab fixed point suggestion using fi(value) is not reliable .I don't know why it suggest that results in overflow.
You can try fi(3)
WL =16
FL= 13
Signedness =1
Try , you can see overflow. For me its not clear . Please help me
Thanks

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