ADC data for Fast Fourier Transform
Why is it common to use ADC data for input sampling to compute Fast Fourier Transform? Why is it a good sampling method for Fast Fourier Transform?
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strncpy chosen by linker from libc instead of rom version
I use 106Micro core and Xtensa toolchain (gcc) for ESP8266 chip.
Not sure what strncpy function is used
According to map file
.text 0x4010077c 0xfa c:/sysgcc/esp8266/bin/../lib/gcc/xtensalx106elf/5.2.0/../../../../xtensalx106elf/lib\libc.a(lib_astrncpy.o) 0x401007b4 strncpy
But also in ROM, there is a function that is already present with the same name
0x4000c0a0 PROVIDE (strncpy, 0x4000c0a0)
Since if function from libc is present in binary, seems that the ROM one was ignored. Most likely I haven't a prototype defined for ROM one (since ESP8266 has many ROM functions not explained, without an ykind of prototype) and due to the libc was chosen.
Now how can I include the ROM version, but keep the in program?
Thanks for clarifications,

C++ reference to volatile object  reasons and effects
I'm working on existing C++ code that has
volatile
references to objectsvolatile vClass & vobj;
I come from
C
so I'm familiar withvolatile
when used to access memorymapped IO like this:*((volatile unsigned int *) 0x12345678) = 0x5
QUESTION
What is the effect of applying
volatile
to (a reference to) an object?I would guess that all of its data members inherit
volatile
but what about if a member function has nonvolatile memory accesses likevoid vClass::AccessMem() {*((unsigned int *) 0x12345678) = 0x5;}
Would that memory access too become volatile?

Embedded RTOS Stop System
I'm learning FreeRTOS on a Cortex M0. (Simultaneously, I'm learning the Cortex as well...). I've got plenty of experience with 8bit MCUs.
I'm going through the newbie tutorials on FreeRTOS and I understand setting up basics tasks and the idle daemon.
I realize I don't really understand what the FreeRTOS is doing to manage the underlying timing mechanicals of the kernel. Which leads to one big question...
What is the ideal way to shutdown an RTOS when you want to turn your device off? Not idle the device, but put your MCU into the deepest OFF there is (whatever you want to call it).
It seems trivial, to idle between tasks, but shutting the MCU off and making sure it stays off, and the RTOS kernel doesn't trigger an interrupt or somethign else to wake the MCU back up...?

How can i use the curve Goodness of Fit?
I would like to use the the curve Goodness of Fit (GOF) in order to compare the rate of resemblance between the orignal signal and the filtered signal in Matlab

How to generate a string of guitar in matlab using karplus strong algorithm
I m searching for that how could i generate the string of guitar in Matlab using karplus strong alogorithm .. But i failed to find it on google or somewhere else.. Please if someone has the implementation of that and then provide it thanks

Number of overlapping frames generated by STFT
Im using
scipy.signal.stft
to get the stft of an audio. No porblem with that and I'm getting the results. But what I don't understand is, when an audio of169600 samples
whose sample rate isfs=44100 Hz
is used to calculatestft
, I get 3 returns asf, t
andZxx
. Here the shape ofZxx
is(2049, 84)
.For calculating
stft
I use a window of size4096
, and as the window type thehanning window
is used. And by default,scipy.signal.stft
uses awindow_size // 2
overlap between frames.My question: Is there
2049
ovelapping frames? if so or if not, how to calculate the number of overlapping frames in stft? if2049
is not the number of ovelapping samples, what does that number mean? 
Run an executable (exe file) that requires user name and password in R script
I was just wondering if there is a package in R that allows to run an executable that requires user name and password?
If yes, can you please provide an example?
so far, I only got
system("C:/Jts/tws.exe")

how to store the response of a system call from R studio to Mac OS X
Not sure how to best ask this. I want to store the response of a system command in R studio Mac.
For example, this command:
system("pwd")
Returns this:
/Volumes/chart/chart
I would like to store the return in a variable like this:
result < system("pwd")
but this does not work.

Connect to Wifi [without Internet] with a high priority [block auto connection]?
I have already asked this question, but it has no answers and I have to keep working. So here I ask this question for the second time.
old question: Connect to Wifi [without Internet] with a high priority?
I have a problem. I develop a android app, which should also connect to a wifi [without internet, just to controll a robot, webinterface: 10.10.0.1].
MY PROBLEM: If I connect to the robot wifi, Android prevents the connection and connect to my default home wlan.
What can I change to connect to robot wifi without problems?
My connection function:
public static void connectToWifi(String ssid, String pass){ WifiManager myWifiManager = (WifiManager) getApplicationContext().getSystemService(Context.WIFI_SERVICE); WifiConfiguration conf = new WifiConfiguration(); conf.SSID = "\"" + ssid + "\""; conf.preSharedKey = "\""+ pass +"\""; conf.allowedKeyManagement.set(WifiConfiguration.KeyMgmt.NONE); List<WifiConfiguration> list = MainActivity.wifi.getConfiguredNetworks(); for( WifiConfiguration i : list ) { if(i.SSID != null && i.SSID.equals("\"" + ssid + "\"")) { MainActivity.wifi.disconnect(); MainActivity.wifi.enableNetwork(i.networkId, true); MainActivity.wifi.reconnect(); break; } } }

Inverse Fourier of a Discrete and Finite Sampling Window
I am trying to find the inverse Fourier of a discrete sampling window with N_f = 11 elements. I am expecting to see a periodic Sinclike signal in the timedomain:
However, this is the output I get:
Why the number of observed oscillations in my output is more than the expected output?
N_f = 11; % Number of samples in the finite sampling window in Frequency domain delta_f = 1; f = [N_f/2+1:delta_f:N_f/2]; wf = ones(1, N_f)/N_f; % W(f):finite sampling window in Frequency Domain N_t =128; wt = ifftshift(ifft(wf, N_t))*N_t; % w(t):Inverse Fourier of the window

Fourier of a Discrete and Finite Window
Assume
W(f)
is a sampling window (discrete and finite signal) in Frequency domain that has only 5 samples with the amplitude of0.2
(as shown in the below figure). If we take the inverse Fourier transform of this filter, we should see a periodic Sinclike continuous function in the spatial domain. What is missing in the following code that I do not get the expected output?N = 2; k = [10:10]; W = max(k(:))min(k(:))+1; wf = zeros(size(k)); wf(1,W/2N:W/2+N) = 1/(2*N+1); wx = fftshift(ifft(ifftshift(wk))); %supposed to be a periodic Sinc (T=2*pi)

Hanning Filter in Spatial Domain
So, Hanning filter is:
H(k)=(1+cos(2*pi*k/W))/2 , W=2*kmax
and based on this, the inverse Fourier of Hanning filter is supposed to be:
h(x) = 1/2delt(x) + 1/4(delta(x1)+delta(x+1))
, where
delta(.)
is the Dirac Delta function. So, ifHk
andhx
denotesH(k)
andh(x)
, respectively:n = 128; Hk = hann(n,'symmetric')'; hx = ifft(ifftshift(Hk));
I tested
hx
andHk
on a sample 1D signal here, and the result seems to be working as I expected. However,hx
does not look as what I expected which is the sum of 3 delta Dirac functions. What is missing in my code? 
What is Setup and hold Time violation?
Why we actually worry about setup time and hold Time violation ? What happened if we donâ€™t setup voilation?

Which one is the best software to design PCB professionally?
I know about the regular PCB design software which are used for student purpose but I want to know about the software which are used for professional or commercial usage.

HiFi speaker hum noise issue and hush background noise while playing music
My speaker makes a hum noise even with no audio input plugged in and when I connect an audio input it makes a hush noise that makes it impossible to listen to anything. What could be the cause of the problem and how can I fix it