A lifetime electronics and software hacker, and complete audio nutcase!

Re: ARM IIR Filter - Why No DAC Output?

Reply posted 2 months ago (07/16/2021)
Brilliant...that worked!So this furthers the question: what is the right way to match filter output amplitude to that of the input? At in-band frequencies why is...

Re: ARM IIR Filter - Why No DAC Output?

Reply posted 2 months ago (07/16/2021)
hi fred h,are you familiar with ASN filter designer?  According to the parameters this is a stable filter. Check attached screen shot.

Re: ARM IIR Filter - Why No DAC Output?

Reply posted 2 months ago (07/16/2021)
Well, I cleaned up code and it's now sort of working! Please see the attached photo. It starts right from the initial filter output. I set the scope to trigger on...

Re: ARM IIR Filter - Why No DAC Output?

Reply posted 2 months ago (07/16/2021)
Thanks Tim, I've removed the ping-pong at at least right now I can see some output post-filter although it's being chunked with inverted pieces - better than no...

Re: ARM IIR Filter - Why No DAC Output?

Reply posted 2 months ago (07/16/2021)
thanks robert,looks like it will be hacking to figure it out. If there's any good DSP practitioners that know the CMSIS DSP library and Cortex-M4/M3 processors,...

Re: ARM IIR Filter - Why No DAC Output?

Reply posted 2 months ago (07/16/2021)
Tim,Thanks for taking the time.Sorry, I should have been more clear. The ADC bus is running at 32MHz, and I have that divided down by 4.The sampling rate is 1.024KHz....

ARM IIR Filter - Why No DAC Output?

New thread started 2 months ago
Hello all,I'm hoping that anyone who's used the arm DSP function (or any similar function) "arm_biquad_cascade_df2T_f32" could perhaps have a look at this code and...

Re: Overdriven Sine Wave through DSP Filter

Reply posted 4 months ago (06/03/2021)
hi,Just wanted to give an update. After some testing I discovered how an overdriven signal causes fold back even when a strong IIR filter is used. In addition I'm...

Re: Overdriven Sine Wave through DSP Filter

Reply posted 4 months ago (05/30/2021)
Yes, these explanations make a lot of sense. in fact, I have previously observed a "regurgitated" signal that had to have come from harmonics at 100Hz (using a FIR)...

Re: Overdriven Sine Wave through DSP Filter

Reply posted 4 months ago (05/28/2021)
thanks philipoakley.Are you familiar with the CMSIS DSP libs? I am thinking that given the filter coefficients generated by ASN (about 12 entries) this must be more...

Re: Overdriven Sine Wave through DSP Filter

Reply posted 4 months ago (05/28/2021)
The BPF is an active filter with gain followed by another gain stage, so clearly it's the post BPF gain stage that needs AGC to limit the clipping! Thanks for your...

Re: Overdriven Sine Wave through DSP Filter

Reply posted 4 months ago (05/28/2021)
Hi ,The signal of interest is just 100Hz, that's all. Amplitude only with as little distortion as possible from noise, phase doesn't matter

Re: Overdriven Sine Wave through DSP Filter

Reply posted 4 months ago (05/28/2021)
Hi Fred, that is interesting. What is the file you sent? Not familiar with the extension/type.I should have been a bit more clear on the AGC. I *can* design the...

Re: Overdriven Sine Wave through DSP Filter

Reply posted 4 months ago (05/28/2021)
Hello all,Many thanks for all these responses. Again, I missed a key piece of info, sorry. The sampling rate will be 1024 Hz. Seems a base 2 value works well or...

Re: Overdriven Sine Wave through DSP Filter

Reply posted 4 months ago (05/28/2021)
Hi,Sorry, I should have known to put down the frequencies which might be useful in such a question. And also didn't mention this requires a bandpass. Since the IIR...

Overdriven Sine Wave through DSP Filter

New thread started 4 months ago
Hello,I'm not a DSP practitioner or even have the math background to fully comprehend the topic, but hoping to get a grasp on something. If a sine wave that is over-driven...

Re: Simultaneous Static and Dynamic Acclerometer

Reply posted 12 months ago (09/21/2020)
Thanks, all good information. The M4 has its limitations but that's what I have in the tool kit right now. I find the CMSIS libraries are a bit funky too. To start...

Re: Simultaneous Static and Dynamic Acclerometer

Reply posted 1 year ago (09/18/2020)
Yes, only the angle relative to the top of the circle.At present there is a basic LPF using 39nF caps on the outputs of X-Y-Z for a cutoff around 250Hz. Once I have...
Hello:The objective is to read the angle of displacement of the device enclosure in a noisy vibration environment. I need just angular displacement but somehow be...

Re: Curve Modelling

Reply posted 2 years ago (02/03/2020)
Ok, thanks for the insight, I'll check it out with your suggestion!

Re: Curve Modelling

Reply posted 2 years ago (02/01/2020)
Hi, Thanks for all of your answers! Appreciated. This is happening in a microcontroller so I have to derive the equation first and then apply the x-variable (current)...

Curve Modelling

New thread started 2 years ago
Hi All,I hope this question is OK here! If not, I'll go away...quickly. I  want to understand how an estimation for a curve fit polynomial could be created. I'm...

Re: Resolution vs Sampling Speed

Reply posted 3 years ago (10/08/2018)
Hello,Ok, that's helpful. Then - if I have sample rate of 1000Hz, can I then run a 512 point FFT every 0.5 seconds and expect to get a proper result? Or, if it's...

Re: Resolution vs Sampling Speed

Reply posted 3 years ago (09/27/2018)
I've tried to find a book with some practical examples of DSP in C, specifically overlap and add, but the problem of course is not knowing all the detail of what...

Re: Resolution vs Sampling Speed

Reply posted 3 years ago (09/27/2018)
Hi,Thanks for the clarification. Yes, correct - I do want to run it continuously.Is this what is called overlap and add?If I remove sample x[0] to x[127], and shift...

Re: Resolution vs Sampling Speed

Reply posted 3 years ago (09/27/2018)
Hi, thanks, your answer!If I understand correctly from your answer, it is not possible to get 1Hz resolution in less than 1 second time frame, no matter what sample...

Resolution vs Sampling Speed

New thread started 3 years ago
Hello:I'm asking this as a bit of a newbie (do embedded prg as well) and did not take DSP at secondary level, and have some exposure to it. I know there's DSP functions...

Re: FFT Speed, FIR Output

Reply posted 4 years ago (05/14/2017)
Hi Rick:You are right about this. I agree that any number of these solutions may work if implemented correctly, but the first step is for me to get a bit of background...

Re: FFT Speed, FIR Output

Reply posted 4 years ago (05/13/2017)
Hi Ced,This was an alternate approach using edge detection/capture. This is on a microcontroller with the inputs and abilities to use, so I thought I would try it....

Re: FFT Speed, FIR Output

Reply posted 4 years ago (05/13/2017)
Hi Rick,This solution also seems plausible, although I'll likely choke in getting from the math into working code. 8(Post filter, in addition to going into an ADC...

Re: FFT Speed, FIR Output

Reply posted 4 years ago (05/12/2017)
David,You are correct, I do not need to reconstruct. I was saying that only in the context of trying to get a grasp on the how, and how-to of the CMSIS libs, and...

Re: FFT Speed, FIR Output

Reply posted 4 years ago (05/12/2017)
This is excellent, I will read your blogs and keep you posted!Roger

Re: FFT Speed, FIR Output

Reply posted 4 years ago (05/12/2017)
Thanks for the detailed reply Steve. I'm going to try some of these things, including the filter type.There's little to no guidance or good examples (documented...

Re: FFT Speed, FIR Output

Reply posted 4 years ago (05/12/2017)
Thanks Fred,That makes sense. Using CMSIS, I found that the relationship between sampling rate changed the bin where the expected signal was. I think there is other...

Re: FFT Speed, FIR Output

Reply posted 4 years ago (05/12/2017)
Hi, Thank you for the detailed reply, very helpful. So, in essence, the FIR may not be required?Then the ADC output's array (outputBuffer) could be input directly...

Re: FFT Speed, FIR Output

Reply posted 4 years ago (05/12/2017)
And sorry, I did not answer your question: ideally, I would like to have the FIR output to "re-create" the signal (as I alluded to in my latest reply) without the...

Re: FFT Speed, FIR Output

Reply posted 4 years ago (05/12/2017)
Hi,I'm more interested in what I can accomplish with the FIR. So let's say I move the anti-aliasing hardware filter to a cutoff of 300Hz. Then I generate a set of...

FFT Speed, FIR Output

New thread started 4 years ago
Hello,Hoping there's some user experience here on the CMSIS libraries that could provide some assistance. Forgive my ignorance on some of these questions. As you...

Re: ARM CMSIS FFT - does it produce correct results?

Reply posted 5 years ago (01/13/2017)
I agree that there's something bizarre with it. Try a sampling frequency that is a power of 2. It seemed that when I tried using it, this was the case. I could only...

Re: Overlap-Save Size for M-1 Points

Reply posted 6 years ago (02/24/2016)
hi, thanks for your answer. can I ask you to go a bit further? I am using CMSIS libraries. I have a buffer with data in:  ADC_Samples, and an output buffer. Tap...

Overlap-Save Size for M-1 Points

New thread started 6 years ago
Hello:I am processing a sinusoidal signal that has an on time of about 100ms every 1000ms - a 10% duty cycle.The capture interrupt takes a 512 sample buffer every...

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