DD4WH
Senior Member

It would be good, if you tested the following audio lib example: examples/HardwareTesting/PassThroughStereo.ino Uncomment the following: const int myInput = AUDIO_INPUT_MIC; Connect headphones to the audio...

Brian, your code runs and performs very well! Well done, thats very good! I added some very small modifications in the example file --> AUDIO_BLOCK_SAMPLES, Serial printing processor load, fixing Serial while command...

Hi Brian, thats excellent news!!! Congrats! I wont have time to have a look at and test this until the weekend. Very good that you were able to optimize both processor load and latency. I will write some info...

It was YOU who put out the term "pro-audio circles" ;-) --> #10 Come on, I am not interested in fairy tales, give me something where I can learn, is there anything you guys published so we can learn from you, or are...

Thats interesting. Did those "pro-audio circles" publish anything (possibly peer-reviewed?), so that others can participate in your knowledge?

Yes, blind audition tests reveal how much of the dynamic range you are able to hear, good young ears (younger than 25 years !) are capable of 120dB of dynamic range, which is about 20 bits. But an ADC with 96dB SNR...

@highly: maybe this is what you need? https://forum.pjrc.com/threads/58054-CMSIS-5-3-0-and-CMSIS_DSP-1-7-0-on-teensy-4?p=219628&viewfull=1#post219628 to be honest, I have not understood from your description what...

Brian, that sounds good! I dont think, the compiler is so smart to use the CMSIS routines. No, it probably doesnt. But AFAIK the CMSIS routine does the same as I did: not using one loop with an index, but putting 4...

@Brian: that sounds really really good, that would be a major achievement to have a partitioned convolution audio object! @highly: hard to say whats going wrong, but it seems you misunderstood the reason for a...

Bit depth: Your ADC PCM1808 will hardly be able to really represent 24bits: according to the data sheet it has an SNR of 99dBA, which translates into an effective resolution of about 16bit. So, there is no need at...

Have a look at the "record queue"-object, which allows you to send realtime audio data from an input (eg. the internal ADC) to the queue object. You will find an example how to use this object in Audio->examples->...

Thanks neurofun! That low budget µSD card adapter worked out of the box when I tried it with a T4 and FrankBs MP3 library! Nice idea and realization :-) Thanks for providing the pictures in post #18, without them I...

Read this: https://www.pjrc.com/store/teensy36_pins.html If you want to waste your time or money and you want your project to be unreliably working or even not working at all, yes, then you should apply more than...

thanks for the hints on where to get the T4 audio board, will try it there. I added the code for T3.6 convolution code to the github. Have fun with the Teensy!

I have been playing around with the code a couple of days on two hardware setups: * T4 and DAC PCM5102a & ADC PCM1808 * T3.6 and Teensy audio shield rev B I have also tried T4 and the Teensy audio shield, but I...

@LoShu: if you use a Teensy 4.0, things will become much easier, because the T4 uses a Teensyduino version with the new CMSIS lib built-in. Have a look at the code here: ...

If you could explain to us what you mean precisely by "ratiometric", we could be better in answering your questions. If "ratiometric" means to you: "The ADC output value is proportional to the voltage at the input of...

Hmm, I have gone through the variables again and I fear we cannot save memory when going to a MONO version. These are the variables used in the Stereo version: FFT length is 256 partitionsize is 128 nfor is number...

Yes, it seems all options work, except the one I am most interested in and which I was originally targeting ;-). If there is any volunteer to put the code into an audio lib LOW LATENCY IMPULSE RESPONSE PLAYER object,...

I see you already answered some of your questions by yourself :-). Here are two possible answers to your "latency in SDR" question: https://www.n1kdo.com/sdr-delay-measured/ ...

Tom, you are probably aware of these resources already, but at these places I have prepared all the info regarding the Teensy Convolution SDR: ...

Tom, thanks for your thoughtful comment! When saying OFFTOPIC, I meant that MY comment on the Si570 was offtopic. However, you are right, this is the PJRC TEENSY forum and this thread is on Software Defined Radio...

The partitioned convolution code has been changed now (is on github), so that any recorded impulse responses can be directly put into the code (without zero insertion). If you have impulse response files as WAV...

@tschrama: I see (at least) three different applications for low latency partitioned convolution: 1.) guitar cabinet impulse resonse (IR) filtering: that is already possible with the existing code with recorded...

Just to confirm: minimum phase lowpass (real valued) FIR filters built with MATLAB also work well with the code and seem to exhibit low latency (as far as I can measure) and good filter effects. (latest code is on...

Hi Brian, yes, the k+31 change is not necessary. The code probably worked from the very beginning, but only with impulse response files, NOT with linear phase FIR filter coefficients (my testing was exclusively done...

The uniformly partitioned low latency convolution seems to work now with the guitar cabinet impulse files AND with low latency (as far as I can test it here). The recent version uses Stereo processing and...

OFFTOPIC: I would recommend to no longer use the Si570 unless you have a very good reason to do so . . . The Si570: * needs way too much power supply current * is much too expensive * is much too sensitive to...

It seems the uniformly partitioned convolution is implemented correctly, BUT the FIR coefficients are not calculated in the right way. Warren Pratt (the designer of the wdsp library, one of the ultimate SDR libraries in...

@Brian: I think I found something. Have you got an impulse response like the one you use for your guitar cabinet defined in C as a const variable, something like this: const impulse = {0.1, 0.05, .... } That...

@Brian: thanks a lot for your very insightful comments and observations. I have to admit that the partitioned convolution as it is at the moment still suffers from a problem: * if the code stays at it is (without...

@MICUPRE: great to hear its working for you! Just some short answers to your questions: 1. https://github.com/DD4WH/Teensy-ConvolutionSDR/wiki/Menu , also have a look at the other entries in the WIKI, maybe you...

same bug here on Windows 8, Arduino 1.8.10, Teensyduino 1.48: when I upload a sketch on T4, the time is one hour ahead (timezone here is UTC + 1).

Hi Brian, thanks a lot for your excellent measurements and information! I have to digest all that and think about that in order to understand fully. * as you said: the good news is that the latency problem is...

Brian! You already found it! You were just one off ;-). It had to be (k + 31) % nfor, NOT 32 . . . It seems the low latency fast convolution code now does what it should. It always has a latency of 128 samples...

Brian, nice to hear from you and especially that you optimized the low latency convolution object! At the moment, there is no need to get your scope (thanks for offering that), because I discovered that the new...

@Brian: before you get out your scope again, one idea: one could test the latency of the code by creating an impulse in software (just a 1.0 in one sample followed by all 0.0 samples) and then output the filtered...

Hi Eric, RTTY decoding as a special case of AFSK is implemented on Teensy here: https://www.kk5jy.net/modem-v2/ and (two different decoders) here: ...

The Teensy 4.0 seems to be able to perform a real-time two channel FIR lowpass filter with up to 21632 taps for audio I2S signals . . . See this code below which filters I2S audio (Stereo: left & right)...

@Joe: OK, now I understand, you mean 135.600kHz, not MHz :-). Yes, that is the expected behaviour of the SDR code to start with that band and that frequency! No, your configuration is not the complete...

@Joe: I do not know, because your setup is unknown to me. For the radio you need: T4, ADC, DAC, Si5351 LO, ILI9341 TFT, encoders, buttons, and a quadrature sampling detector (and RF input lowpass or bandpass filters)....

Do not hesitate to ask if you have any problems with the code!

@Joe: the only reason I did not use PJRCs audio board is that it did not work with my wild wiring :-). Now with version D available it is no problem to use the PJRC audio board and the T4. The Convolution SDR code...

@Joe: the Convolution SDR makes only very limited use of objects, it uses the audio lib queue object to gather the audio files from I2S and to push the files to I2S after treatment. ALL the audio processing,...

@MICUPRE yes, a larger TFT with the ILI9341 controller and the same number of pixels should work. If you want higher resolution, you would have to completely reprogram the display. Softrock should work. Does it...

Joe, not sure if I understand correctly: Do you mean a sketch to check functioning of the T4 and audio board? You could use the StereoPassThrough example from the audio lib. Or try the convolution filter object...

Oh, I was not aware that the syntax is still evolving, that explains a lot. For the moment, I tried to reproduce your RAM-Info, but I could not get imxrt-size.cpp to run . . . So I put together a...

Thanks Kurt! I still have problems understanding the syntax . . . Maybe it would be good to give some dummy examples and let you experts comment on that ? Is the following syntax/use example correct? I want to...

@Paul: thanks a lot for the graph and the explanation! That is what I have been waiting for :-). It was very hard (and still is hard) to understand how the memory is composed and especially how to use the different...

Hi Joe, I am pretty sure you did not have the Teensy Convolution SDR on a Teensy 3.2, because the Teensy Convolution SDR does work only with Teensy 3.6 or Teensy 4.0. It must have been a version of the Teensy SDR,...

The first one is intended and is no error ? It compiles for me and the fast log-approximation code is being used by the spectrum display code For the second problem you have to define your own hardware and define the...

First of all, it would be good to know what you want to do with the FFT!? Then it would be easier to decide whether you need a real FFT or a complex FFT. Regarding the code you posted: * you should NOT use the...

Possibly! Would be interested to hear if it works and please post a photograph of your setup.

You could also have a look here, Brian has done something useful for the Teensy 3.6: https://circuitcellar.com/cc-blog/fancy-filtering-with-the-teensy-3-6/ ...

I never had crackling noise with DAC alone, the ADC was the problematic part, so my thought was to add 100 Ohm resistors to all ADC clock lines (and to the master clock for DAC). I did not check systematically however....

Thanks to Henk, we now have an Excel file summarizing all pin connections between the ADC, DAC, T4 and the ILI9341 TFT for the current T 4.0 Convolution SDR ...

Yes, you can find an example here: https://forum.pjrc.com/threads/57267-Fast-Convolution-Filtering-with-Teensy-4-0-and-audio-board?highlight=convolution It uses a forward 4096-point-FFT, a complex-multiply with a...

@defragster @mjs513 , just for your records My experience with overclocking is the following: Yesterday, I could run your Buddhabrot example at 1008MHz for more than one hour without problem (I use set_arm_clock...

Thanks again for pointing me to the bugs! Now the software compiles for Teensy 3.6 (latest version is on github). I have also tested the fixed version on my T3.6-based SDR and it plays fine. For Teensy 3.6,...

Hi MICUPRE, sorry for that: I seem to have messed up the Teensy 3.6 configuration while I was working on the T4 version (which uses another TFT library and thus some other commands for printing text). I will...