# Questions tagged [c]

C is a high level (i.e. not assembler) programming language often used to program DSPs and other embedded microprocessors as well as being used for systems programming. Features of the language make it especially suitable for programming hardware and writing device drivers.

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### filter single radio station with sdr [closed]

I want to write a program to filter a single radio station using SDR. Not for any application just a stepping stone to learn. I am going to use C so it is easier for me to see the steps and things ...
73 views

### simple iir filter implementation in C++

I am programming the simplest way of implementing and IIR filter. However, I am struggling with the use of buffers. Do any of you have any simple implementation of an IIR filter implementing manually ...
25 views

### Implementing a beamforing algorithm for radar

I want to implement Real-time Radar Beamformer algorithm in C language, and the Conventional beamforming algorithm is as follow : ...
110 views

### FIR filtering with C++ to a sinewave

I am translating my FIR filter script from python to C++. My problem is that I am following a workflow which in theory should work but I get weird results. 1st. I create a signal from 1 and 50 Hz sine ...
30 views

### How to apply an offset to a complex exponential without chopping it off?

I am trying to encode a bitstream as offset in a complex exponential, but when I do, the sinusoids get chopped off. Do I need to apply a lowpass to the bitstream or is there a more elegant way? ...
85 views

### Fast algorithm for n-dimensional DCT

I need to implement an encoder which compresses a 5-dimensional structure of 10 bits values. Each dimension has between 4 and 12 elements. If a dimension ever has more than 12 elements, it is ...
27 views

### Are there any State Space Control C libraries?

I'm searching for a C library which implements methods needed for state space control (e.g. state feedback controller and state observer equations). Googling various terms only brought up a non-C (C# ?...
64 views

### Sampling a low-frequency sound doesn't work at some sampling rates

When sampling a low-frequency sound (like a 55Hz sine wave) I hear an additional high frequency sound at certain sampling rates, but not at others. This happens in Audacity and in my own program. For ...
73 views

### Problem with natural logarithmic function in fixed point notation

I am facing a problem with natural logarithmic function in fixed-point notation. Let's say $$x = 0.54, \qquad\text{then}\qquad \ln(x) = -0.616186, \qquad\text{a negative number} \tag{1}$$ Then in ...
28 views

### Changing Coherence function from float to fixed point

I want to calculate the coherence between two audio signals. After referring a few websites, I found that the coherence is calculated by using the equation $(1)$ which is as follows \rm Coherence = \...
124 views

### Coding an LFO in C

I want to know how I could implement a Low Frequency Oscilator on a simple synth I've coded in C. First in order to understand how to make this happen I would like just to modulate a sine wave by a ...
136 views

### Calculating the true values of biquad filter coefficients from normalized form

I have a C code in which the IIR filter(BiQuad) uses only 4 (normalized) coefficients per stage (a2/a0,a1/a0,b2/b0,b1/b0) instead of 6 coefficients (a0,a1,a2,b0,b1,b2). I know that the value of a0 is ...
119 views

### Comparison of results with Direct form1 and Direct form2 implementation of IIR filters

The results obtained from Direct form1 and Direct form2 implementations (in C language) of IIR (BiQuad) filters are a little different. In the implementation, i have made the b0 coefficient as 1. So, ...
38 views

### Carrier frequency offset in Bell 103 FSK system

This question is a sequel of the discussion that started in this question. Dan Boschen suggested some very nice solutions to decode a Bell 103 FSK signal. I am especially interested in decoding the ...
49 views

### What's wrong with this implementation of my IIR filter?

I posted this originally in the electronics stack exchange, as it's for an electronic purpose (digitally controlled boost) but it was pointed out to me that this would be the more appropriate place - ...
177 views

### Decoding a PCM BFSK signal (Bell 103)

A recent project requires me to get into some basic DSP, in C. I receive PCM samples of a BFSK signal (Bell 103). The sample rate is 8 kHz. The mark and space frequencies are 1070 and 1270 Hz. To ...
19 views

### Looking for a good implementation / API for the radon transformation in C/C++

I am currently working on a project about Metal artifact reduction (MAR) for CT images. I am looking for a good implementation of the radon transformation and a backtransformation, ideally filtered ...
60 views

### Calculating Cross Power Spectral density between two complex signals

I have a small misunderstanding of cross power spectral density between two complex signals. I know that it is the Fourier transform of cross correlation between two signals. Let's say the complex ...
72 views

### dB SPL readings differ from external sound level meter?

I'm trying to write a program that takes values from a MEMS microphone and calculates the dB of the incoming audio data. The microphone i'm using is this: https://www.mouser.es/datasheet/2/218/...
73 views

### FIR Filter implementation without padding

Is it possible to implement FIR filtering action without padding the input and coefficients? i.e. Let's say if the input and filter coefficients are of size 4, then the output will be 7 samples. So, ...
82 views

### FIR Filter implementation vs Linear convolution implementation

I came across a C code for the FIR filter on one of the websites. It is as follows ...
6k views

### How can I generate a sine wave with time varying frequency that is continuous, in C?

How can I generate a sine wave with time varying frequency that is continuous? How can I resolve the following problem? I want a continuous graph. I'm generating this simply like this: ...
46 views

### Given a static time domain signal, why does the magnitude oscillate in the frequency domain after FFT?

I'm trying to: Generate a sine wave in the time domain (locally within my program at 500 Hz). Analyze it with FFT Print the results in the frequency domain. The expected results are that since the ...
53 views

### Kalman filter using only location information

I have never used a Kalman filter. Is it possible to implement a Kalman filter using only location information? In addition, if you can implement it, what kind of procedure should be used to program ...
168 views

### How to work with portaudio?

I am working in a project to record audio and process in real-time in C.For starting, I wanted to check how it works. I downloaded the pa_stable_v190600_20161030.tgz from here. I ran ,/configure and ...
168 views

### Understanding and converting Matlab's coarse frequency compensation function

I am trying to understand and convert to C Matlab's coarse frequency compensator the documentation for which can be found here: Documentation Matlab's design itself is based on this IEEE paper: ...
91 views

### Translating Matlab scrambler function to C

I am trying to implement the following matlab function in c: Mathworks scrambler Function Documentation This is the code I've written: ...
3k views

### How to design a digital filter in python that will run over an uC?

I am trying to implement a digital filter over a uC (it doesn't really matter which filter and which micro controller because I'm looking forward to learn how to do it in the future with different ...
100 views

### Hyperbolic sine “sinh” in fixed-point?

As part of an audio peaking filter calculation, I need to implement hyperbolic sine ("sinh") function in a fixed-point arithmetic (fixed-point DSP processor). What is the proper way to do this?
985 views

### Hilbert Transform in C provides possibly strange results

I am calculating some signals that depend on the Hilbert Transform and, after following various guides online and SO, my function looks like this: ...
509 views

### How to properly filter a BPSK demodulated signal?

I am new to this field and yesterday I began a project for BPSK modulation. So this is what i did: $\ x(t) = 0$ or$\ 1$ binary data $\ Fs = 15$ sampling frequency kHz $\ Fc = 10$ carrier ...
76 views

### BPSK demodulation [duplicate]

For experimental reasons i created a function that helps me to modulate a signal using BPSK, the input signal is {1,1,0,1,0} and it works fine ...
157 views

### Circular buffer wrap around with chorus effect

I am developing an embedded DSP audio processor and am trying to implement a chorus effect. To my understanding, the chorus effect is multiple delayed versions of the original signal, where the delay ...
6k views

### What exactly is “sparse representation”? [closed]

I saw a recommended topic for the final project in my university called "dsp and dip applications using sparse representation techniques (MATLAB, C, C++)". I consider taking this topic as my final ...
417 views

### how can I make a simple lowpass filter with this constraints? [closed]

I'm searching for a simple low pass filter code in C with this constraints a modulable frequency cutoff (how can I convert all these crazy coefficients into a frequency?) I could change with a slider....
80 views

### Pitch fluctuates unexpectedly in simple sine function

I wrote a very basic C program to play a sine of a user-specified frequency. In the interest of portability, I have it spit values directly to stdout, so hopefully you can reproduce my problem on your ...
80 views

### Difference between filtering using Matlab and filtering using C code generated by Matlab

hi，has anyone used Matlab coder to generate C code for a filter? Here is the thing: I tried to filter the same audio signal using Hamming window-based FIR bandpass filter, the filter is designed by ...
451 views

### How to convert floating point code to fixed point?

I am working on converting a floating point MATLAB code into fixed point C code. The code is to be run on a DSP platform, the specifics of which are yet to be decided. I'm new to floating point to ...
769 views

### IIR Lattice Filter in C programming

I would like to implement Lattice IIR filter in c, i can't defined the value of gN, i know that x(n) = fN(n), but how to initialize gN ?. you can find the algorithm here : n
45 views

### Finding a change in a signal

I am looking to some C algorithm(for MCU), where I have these signals : First graph you can see that there is an event in the middle and it goes back to normal, second and third there is some event ...
852 views

### Trouble with fixed-point arithmetic 2nd order IIR implementation in c

DSP newcomer here! I am tinkering around with a TI DSP and am trying to implement a second order IIR filter in C. Input is 16 bit 2's complement, as is the output, the accumulator is 32 bit wide. I ...
631 views

### How can i measure soundcard latency?

I want to write sonar/radar like sample application. For sake of simplicity (and not to use Arduino and specialized RTOS) - I simply used using audio in/out analog ports of a motherboard integrated ...
2k views

### Convolution and Deconvolution in C

I understand the theoretical foundations of convolution, but now that I'm trying to program it I'm having some issues conceptually. Say I have two blocks of 64 audio samples each. I also have access ...
2k views

### Decimation function implemented in standard C [closed]

I'm thinking in a decimation C function. The prototype of the function is: decimate(int N, float input[], float r, float output[]) where N is the length of array ...
805 views

### Biquad filter from Matlab to C using “tf2sos”

This is a biquad implementation I use: ...
654 views

### 4th order high-pass filter on a DSP: standard or biquads?

I have two C implementations of 4th order high-pass filter (fs = 16 kHz, cut-off=100 Hz, designed using Matlab ...
105 views

### Detection milliseconds signal using a DVB-T dongle as SDR in C (need idea)

I have probably amateurish problem. Assume that we have a USB tuner DVB-T + connected antenna. I would like to write a program that will detect the signals of at most a few milliseconds. Signal ...
333 views

### How to use linear predictive coding to compress voice diphone samples?

I'm working on an experimental diphone / unit selection speech synthesizer for my native language which lacks good speech synthesizer for blind people. The problem is that recorded unit library can ...
I can't find anything on this topic, so either I'm in the wrong direction or else there is just nothing about it on the internet. So let's say I have 3 $b_i$ coefficients ($b_0,b_1,$ and $b_2$) and 2 ...