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Thread: Teensy Convolution SDR (Software Defined Radio)

  1. #226
    Thanks Frank! The links provided help...
    Cheers,
    Jim

  2. #227
    Senior Member DD4WH's Avatar
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    Morse code (CW) decoding is now available in the Teensy Convolution SDR.

    Click image for larger version. 

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    We have implemented the decoder version supplied by Loftur (thanks a lot for putting that into the public domain! https://sites.google.com/site/loftur...olour-Graphics) based on an algorithm from a Master thesis from 1973. It is the same version as available for the UHSDR software.

    This is a first version, so there is some caution necessary:

    * the threshhold for detecting the Morse pulses (CW thresh) has to be manually adjusted according to the band noise, it has to be well above the band noise and well below the signal strength of the Morse signal
    * the tone detection uses a narrow bandpass filter (Goertzel) at 700Hz, so your signal MUST be tuned at 700Hz above or below the tune frequency (depending on whether you use USB or LSB demodulation). This will be made flexible and adjustable for the user in the next version
    * there is an automatic adjustment called ATC, but I have not yet experimented much with that
    * of course, the human brain is much much better than a machine in decoding morse code signals buried in noise: so, do not expect miracles from this simple decoder

    The latest version is on github: https://github.com/DD4WH/Teensy-ConvolutionSDR

    Have fun with the Teensy!

    Frank DD4WH

  3. #228
    Senior Member DD4WH's Avatar
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    There is now a small red symbol flashing in the same rythm with the Morse code tones when CW thresh is properly adjusted (it should not react to noise, but to the Morse code: this is essential for proper decoding). Also wpm display gives the speed of the morse code in "words per minute". One standard "word" is 10 dots and 4 dashes as in the word "Paris"



    What we hear is a signal by radio amateur Gyuri (HA5JI) from Hungary communicating with (probably) IK1WQK (we can not hear the QSO partner)
    Last edited by DD4WH; 09-27-2019 at 06:43 PM.

  4. #229
    Senior Member DD4WH's Avatar
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    The Teensy Convolution SDR goes 4.0



    Here, it demodulates FM stereo at 256ksps sample rate using the processor intense atan2 function with the double precision FPU of the Teensy 4.0. Processor load is now about 61% (in the video it is 44%, but I changed a bunch of things).

    For testing, I built up a new machine on a perf board with a common ground plane using:

    * Teensy 4.0
    * ADC PCM1808 module
    * DAC PCM5102a module
    * TFT ILI9341 2.4
    * quadrature sampling detector board containing:
    * Si5351 local oscillator
    * Johnson counter 7474
    * switching mixer == tayloe detector
    * OPamp after the mixer
    * three encoders
    * one cheap joystick containing the functionality of five pushbuttons
    * the antenna is a 2 x 0.75m wire connected directly to the quadrature sampling detector board

    The software is now usable with the Teensy 4.0 OR the Teensy 3.6. Use the compile time switch in the first script lines before compiling.

    https://github.com/DD4WH/Teensy-ConvolutionSDR

    There is plenty of room for optimization, eg. the IIR filters in the FM receive path have to be substituted by phase linear FIR filters to enable better stereo diversity.

    All the best,

    Frank DD4WH

  5. #230
    Senior Member DD4WH's Avatar
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    For those interested, this is the audio flow in software for demodulation of stereo wideband FM. If you have any suggestions for improvement, I will be very happy to hear about that! Also those interested in helping to decode RDS ID and text messages, please do not hesitate to post here.

    Click image for larger version. 

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  6. #231
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    Hi

    I have downloaded the most current version (2019_10_08). I'm using the Teensy 3.6. The relevant Audio shield has not been connected yet. I plan to use my own SDR that I built, the SDR has a si5351 onboard.

    I have been playing around with the code of the version earlier to this around Oct 3. The plan then was to display the screen and then work out the controls and their operation. No SDR was connected at the time, but the idea was to get a more general feel of the operation and the layout of menu items. I made the changes necessary I the library files based on the instructions and the screen displayed the necessary information and with trial and error and studying the code, I worked out each of the controls.

    I upgraded Arduino and that broke all the earlier work done on the libraries and so I started afresh.

    I now downloaded the version available but did not realise that it has been updated and this showed a number of errors at compile time which I corrected mostly library etc. I uncommented this line #define HARDWARE_DD4WH. However, I see from the code that several errors came up that did not show on the earlier version and example is DrawFloat which states that the member does not exist.

    Where do I set the code to use 3.6 instead of T4. There are some other bugs that are coming too for example on line 248 there is
    #elif
    #include <ILI9341_t3.h>
    #include "font_Arial.h"

    The above is an elseif with no condition.

    I have rechecked and rechecked the code, I'm not sure what I'm missing,

    Thank you.

    /MICUPRE

  7. #232
    Senior Member DD4WH's Avatar
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    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 repair that the next days and inform you as soon as the T3.6 configuration is working again and tested on my equipment. Will also try to clarify the setting of the compile time switches (which #define to uncomment/comment).

  8. #233
    Senior Member DD4WH's Avatar
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    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, compile with uncommented
    Code:
    #define HARDWARE_DD4WH
    and choose Teensy 3.6 180MHz in the Arduino compile options

    For Teensy 4.0, compile with uncommented
    Code:
    #define HARDWARE_DD4WH_T4
    and choose Teensy 4.0 in the Arduino compile options.

    For Teensy 4.0, you will find a menu entry where you can choose the CPU frequency you want. Beware to have a good heatsink installed when going over 600MHz.

    I have been able to run the T4 Convolution SDR at 948MHz for hours. Every CPU frequency above 948MHz causes the radio to crash (although not necessarily immediately . . .). But 948MHz is really fast enough for everything you would dream for in this radio.

    Have fun with the Teensy Convolution SDR,

    Frank DD4WH

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