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    Hi Esteban, while looking at your video, I...

    Hi Esteban,
    while looking at your video, I realized the rather high temperature of the T4 processor, if I read correctly it is 58 degrees C in the enclosure.

    That seems to me rather...
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    hi Tisho, very nice you got your SDR to...

    hi Tisho,

    very nice you got your SDR to work!!!

    I am also very impressed about the noise floor figures.

    When comparing with Sherwoods figures, here: http://www.sherweng.com/table.html
    ...
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    Excellent work! Really looking forward to testing...

    Excellent work! Really looking forward to testing and comparing :-)
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    Hi Les, * in WFM, the default is NO spectrum...

    Hi Les,

    * in WFM, the default is NO spectrum display (because of the high processor load at 256ksps sample rate), so this is intended behaviour
    * without a spectrum FFT being performed, there is...
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    Hi Joe, there are several aspects with this...

    Hi Joe,
    there are several aspects with this according to my experience:
    * convolution filtering is computationally less intense if you substitute FIR filters from about 60 taps onwards, so even...
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    @Karlchen: did you test one of the 2xfo-setups...

    @Karlchen: did you test one of the 2xfo-setups you posted in #403 in a real SDR frontend? I would be very interested in your experiences and the performance differences compared to a 4xfo setup!
    I...
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    Oh, thats a pity. A few years ago I purchased...

    Oh, thats a pity. A few years ago I purchased that chip in SOIC package, so at least they used to produce them for some time in history :-).
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    @Karlchen: you are right: switching time !=...

    @Karlchen: you are right: switching time != bandwidth of the chip.
    All recent designs for QSD frontends I know of now use the 3253 instead of the 4066. Potato offers a 3253 in SOIC16 package (easy...
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    OK, understood! However, I think the limiting...

    OK, understood! However, I think the limiting factor will not be the noise of the OP-Amp (most QSDs use low noise types, e.g. the LT6231 has 1.1nV/sqrt Hz), but the noise coming from the fast updates...
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    @Les, @Karlchen: for ICs with higher frequency...

    @Les, @Karlchen: for ICs with higher frequency capability, maybe you can find something useful here: http://www.potatosemi.com/

    They have 7474, 3253 and alike with switching frequencies up to 1GHz...
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    Congratulations! Very nice! I think the...

    Congratulations! Very nice!

    I think the filters can be built with SMD components. Use good (and expensive) NP0 capacitors.
    The coils are more critical, those with high Q are bigger and cost more...
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    I have to read a lot, because as a biologist many...

    I have to read a lot, because as a biologist many of this electronics / DSP stuff only becomes clear to me by reading the references :-).

    As far as I understand it, by using one ADC for the I...
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    Nyquist always plays a role ;-). We are using...

    Nyquist always plays a role ;-).
    We are using two ADCs with 256ksps each and we digitize I AND Q, so the resulting bandwidth is 2 x Nyquist == 256kHz bandwidth.

    That is the reason why we can...
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    Hi WH7U, very interesting simulations and...

    Hi WH7U,

    very interesting simulations and figures! However, I do not understand your scaling of the axes very well. Is the y-axis linearly scaled? Would be good to see a dB scale. And x-axis is...
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    Hi Esteban, thanks for the information! ...

    Hi Esteban,

    thanks for the information!

    How did you measure sensitivity? And which bandwidth/demodulator did you use? Standard sensitivity measures are usually made in SSB with very narrow...
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    Hi Esteban, that looks really great! And it...

    Hi Esteban,

    that looks really great! And it will be a great help for anyone trying to build a Teensy Convolution SDR (or any other QSD-based SDR).

    I am really curious about the Msi001...
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    How about this "ready-to-use" solution on the...

    How about this "ready-to-use" solution on the Teensy?...
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    I can confirm, it seems Italy is a little special...

    I can confirm, it seems Italy is a little special concerning highly exaggerated shipping costs.
    Here, in Germany, ordered at exptech: two T4.1 did cost 63,28€ == 31.64€ for ONE Teensy 4.1 including...
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    Hi Bob, really struggling here with the...

    Hi Bob,

    really struggling here with the OpenAudio lib . . . there are several issues:

    * the codec code for tvl320 seems redundant, it is present in the standard audio lib AND in the OpenAudio...
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    @WH7A: great to hear that! Could be an option to...

    @WH7A: great to hear that!
    Could be an option to lower the SPI speed for the TFT (70MHz), see one of my posts above.
    The QRP labs receiver is great! But it uses an audio transformer after the OP...
  21. Very interesting! Would be nice of you could post...

    Very interesting! Would be nice of you could post some more information, eg. name of the NGO or some preliminary details about the ventilator?
    You probably know this Arduino-based design?...
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    Hi Bob, thanks for the code on your homepage!...

    Hi Bob, thanks for the code on your homepage!
    However, I cannot manage to run it. I have the following problems:
    * I copied OpenAudio_ArduinoLibrary from chipaudettes github to my Arduino lib...
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    ... mine left PJRC on April, 21st, spent 18 days...

    ... mine left PJRC on April, 21st, spent 18 days in San Francisco and has now been held in customs in Frankfurt for two days, we´ll see when it arrives ;-).
    I purchased two T4.1 with exp-tech, which...
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    Excellent to hear! Have fun with it, thats the...

    Excellent to hear! Have fun with it, thats the goal ;-)

    Does it work with the original tft.begin settings (70MHz) ?
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    Hi Bob, excellent work! Very nice and easy to...

    Hi Bob,

    excellent work! Very nice and easy to use! As you requested, some first observations of a test with Teensy 4.1 & Teensy audio shield rev. D:

    * I had to adjust the input and volume...
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    Sounds exciting! I have to read more about that...

    Sounds exciting! I have to read more about that in order to understand what you did in the code!
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    One recommendation: * Do NOT mess with any of...

    One recommendation:
    * Do NOT mess with any of the calibration variables before you are perfectly sure, that everything is working correctly. Leave every calibration variable as it is !
    * the...
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    @WH7U: I guess you are nearly there :-). * it...

    @WH7U: I guess you are nearly there :-).
    * it would be best, if you have the latest Teensyduino software 1.52 and use that for compiling
    * the TFTs behave differently, even if they all say they are...
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    Excellent! It should not have an influence on...

    Excellent!
    It should not have an influence on the sound quality, but only on the ability to reproduce Stereo signals accurately, I think.

    Edit: "time division multiplexing": not sure, what that...
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    Teensy 4.1 pinout missing details

    The PJRC Teensy 4.1 page lacks some detail about the pins between the processor and the SD card (the backside of the pinout card is missing). Would be good to have them included on this page:...
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    Hmm . . . 1.) the main filter is a complex...

    Hmm . . .
    1.) the main filter is a complex convolution filter which calculates the coeffs with a function in the sketch. It does NOT use the CMSIS FIR filter function
    2.) the CMSIS FIR filter is...
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    I do not know what that means . . ....

    I do not know what that means . . . "time-reversed order"?
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    Hi Les, nice to hear that you had success in...

    Hi Les, nice to hear that you had success in building the SDR!

    * with T4.0/T4.1, you do not need to install a newer version of CMSIS. This is only necessary with Teensy 3.6
    * I would strongly...
  34. My recommendation would be not to use rev B/C...

    My recommendation would be not to use rev B/C with wires and T4.x. It will create all sorts of problems, I spent a lot of time on this and did not manage to get T4.0 & audio shield to work properly...
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    Thanks Kurt, thanks Michael! Excellent! Plugged...

    Thanks Kurt, thanks Michael! Excellent! Plugged out the Teensy and beginning to read now :-).
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    Need to read something about "cache" and how it...

    Need to read something about "cache" and how it works for the different RAM regions including EXTMEM. Do you have any suggestions where I could find something (beginners level, please :-) . . .)
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    Win10, T4.0 with ADC PCM1808 and DAC PCM5102a and...

    Win10, T4.0 with ADC PCM1808 and DAC PCM5102a and Ili9341_t3n (@70MHz) runs well with TD 1.52 beta6. Same setup also plays mp3 from SD card (flying wires soldered to a µSD-card adapter) with FrankBs...
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    @FrankB: * the sketch is for guitar cabinet...

    @FrankB:
    * the sketch is for guitar cabinet emulation: combines applying large impulse responses to audio together with minimizing latency. (and it consumes a lot of processor power and a lot of...
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    @manitou, @mjs513: thanks for pointing me to the...

    @manitou, @mjs513: thanks for pointing me to the speed change code for PSRAM SPI!

    I tried using T4.1 plus two soldered PSRAM chips and Teensy audio shield with partitioned convolution filtering...
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    Win10, Arduino 1.8.12, TD 1.52 beta6, T4.1 and...

    Win10, Arduino 1.8.12, TD 1.52 beta6, T4.1 and Teensy audio shield version D, 2 PSRAM chips, using EXTRAM as part of the audio buffering --> works with partitioned convolution filtering


    /*
    *...
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    at the moment I am experimenting with using 2...

    at the moment I am experimenting with using 2 PSRAMs with T4.1 for audio processing (guitar cabinet impulse - partitioned convolution filtering).
    However, it seems the PSRAM is too slow for large...
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    Win10, Teensy 4.0, Teensy Convolution SDR, works...

    Win10, Teensy 4.0, Teensy Convolution SDR, works well!

    Win10, Teensy 4.1, 2 PSRAM chips, tried several example sketches, including PSRAM memory display ("16MB"), works well so far, however the...
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    Excellent! :-) FLASH: 36048 0.44% of...

    Excellent! :-)


    FLASH: 36048 0.44% of 7936kB (8090416 Bytes free) FLASHMEM, PROGMEM
    ITCM: 24288 74.12% of 32kB ( 8480 Bytes free) (RAM1) FASTRUN
    PSRAM: 16 MB
    OCRAM:
    524288 Bytes...
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    Soldered a second PSRAM chip to the Teensy 4.1...

    Soldered a second PSRAM chip to the Teensy 4.1 underside and updated to Teensyduino 1.52 beta5.

    Using Pauls´ sketch from #478 it detects both chips:



    External RAM test

    PSRAM size is 16...
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    I received my two Teensy 4.1 ordered from ExpTech...

    I received my two Teensy 4.1 ordered from ExpTech two days after the order! My beta T4.1 sent from PJRC on April 22nd still seems to circle around somewhere in San Francisco . . .
    Some questions:
    *...
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    My T4.1 beta test board also is stuck with USPS...

    My T4.1 beta test board also is stuck with USPS in San Francisco since April 24th . . .

    I just ordered two T4.1 at exp-tech (32 EUROS each, thanks for the hint, sstaub & Michael), I bet those will...
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    Hi Keith, not sure how your frontend looks like,...

    Hi Keith,
    not sure how your frontend looks like, but a standard quadrature sampling detector does not need standard SBL-1 mixers and a splitter with the associated high losses. Do you use a "Tayloe"...
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    works very well with Windows 10 and Teensy...

    works very well with Windows 10 and Teensy Convolution SDR.

    Special thanks to you, Paul, for fixing the daylight saving issue ;-) !

    Central European Summertime seems to be supported by T1.52...
  49. Thanks Paul, for that quick and important info...

    Thanks Paul, for that quick and important info about the difference between T4 and T3.6 RTC setting on upload.

    I can report that the bug is still there with Windows 10 and Teensyloader 1.52 beta3...
  50. Is there any way to fix the annoying bug that...

    Is there any way to fix the annoying bug that causes the (S)RTC to lag one hour behind when I load a program into my Teensy?

    [I am using about 40 Teensy 3.6 in different audio and ultrasound...
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