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Teensy 3.2 w. Audio Board

When I first read about the Teensy SDR Receiver by DD4WH  resp. initially presented by Rich, it was just a question of the OnlineshopToFrank-time, how long it’ll take until it was on my desk 🙂

There are 4 videos on Youtube by “Franz DX”, that showed an impressive small and still interesting standalone SDR,  start with video #1 That videos inspired me to think about replica or derivate projects.

With my first quick setup I was very surprised. It performed much better, than I would an arduino-like platform expect to perform and that is mainly due to the 32 bit Cortex-M4 based board in combination with the SGTL5000 Audio board. It simply beats the computing capabilities of the – standard – Arduino in quite all points. CPU, Memory. Also there is a very active community around it chatting and helping each other in the forum. The extra memory makes it a 2016-ish feeling and the 96 MHz are great for all sort of calculations!

The creator and many contributors have built up an excellent C++ based library ecosystem around the platform, that makes it easy to take off in no time. That said, most of them are actually the arduino libs, with some tweaks. That saves you a lot of time when driving some accessory devices like LCDs etc. Especially the audio library is worth a look. The workshop video is fun to watch!

Personally I don’t like the Arduino IDE, because it tries to hide a lot of “complexity” of the underlying language. Might be nice for beginners or a short sketch, but not so cool when you’re about to put serious effort into development. Therefore I prefer to wrap Eclipse for Arduino around the Teensy/Arduino libs and build tools. It simply gives you a solid editor, common IDE features and doesn’t force you to work in a notepad style with this .ino skatches. Simply pure C++, as it should be. The How To section will guide you to set it in place for Teensy development. Since I’m bit a Jetbrains fanboy I’d like to see a CLion wrapper around the avr tools that actually work. I’ve used eclipse for many years and it’s just a not my number 1, but not a bad choice, since it allows good IDE aided development flow for the entire development life cycle.

Currently I’ve got a reasonable long list of SDR projects, that I’m doing some good progress on. I’m not about to jump right into a new project based on the Teensy, but it’s good to have it in the toolbox. It’s value for the hobbyist as a development platform is worth the price. So expect it to approach here and there in my future projects.

One new fun-project will go to my list: Combine the famous C64 SID 6581 chip – with all it’s analog, non linear unique sound – with some tiny DSP. Guess that’s a perfect math and think about the nice synthesizer samples, generated realtime on the SID! Non HAM project, I know, but in the end all is about waves 😉

Here is a first short video about my initial setup with a FFT on a post stamp oled display. Just ordered a higher res color SPI display, that should manage 30 frames per second.

08th Aug 2016: Updated the display and code:

GR-OSMOSDR updated to use SDRPlay API V. 1.95

I’ve always wanted to use the SDRPlay with my GNU Linux computers, that I’m usually working on. The previous version of the GR-OSMOSDR provided by the SDRPlay-Team was somehow not working and looked unfinished  ….at least not on my side, so I decided to implement the 1.95 API version on my own.

It might still be a bit unstable, but looking forward to some tests and review results to get this right.

The sources are here on Github and a short shaky handy video with some explanations here:

Open Matters, Slides & Links

This post will be updated soon. I’m waiting to receive the video files from the event hosts.

Today I’ve received the video from the event host. Excuse the poor quality. Audio/Video is a few ms out of sync so it looks/sounds a bit like bad dubbing 🙂 Anyway, enjoy!

Attached you’ll find my slides from my SDRA-2016 conference talk:

PDF Download



Please also take a look at my post @hamspirit.de https://www.hamspirit.de/5881/




SDRPlay on linux – work in Progress

Just a short post:

The SDRPlay linux adapter “play_sdr”  https://github.com/krippendorf/SDRPlayPorts is nowenough stable to generate quality FFTs / analysis in Baudline:

8000000Hz SampRate


Share your SDRPlay over the Internet / Browser with OpenWebRX

I’ve done a small proof of concept to use OpenWebRX with the SDRPlay. This would allow to share the SDRPlay over a WAN connection and just leave a RaspberryPi running at home. Wouldn’t that be nice? Currently it uses the sample play_tcp code that only outputs 8-bit IQ. I’ll change the code to get out the full 12bit along with some setup script to quickly setup SDRPlay with OpenWebRX. OpenWebRX was created by András Retzler (HA7ILM). (See his BSc. thesis here). He made it very easy to use other receivers, by just passing the IQ samples. Looking forward to be ready in a few days 🙂


—- Update 2016-APR-06

Pushed a 16bit play_sdr version to my repo https://github.com/krippendorf/SDRPlayPorts – Now OpenWebRX still just likes uint8….

Looking at 80m band, play_sdr16

OpenWebRx Settings 16bit

maximum Zoom

OpenWebRx SDRPlay 16bit


— —- Update 2016-APR-09

Merged play_sdr16 into play_sdr… testing with baudline:


SDRPlay now plays on linux

Started to play with the SDRPlay C/Linux api and forked RTL_TCP to PLAY_TCP. That allows to run the SDRPlay e.g. on a Raspberry PI in your local network. The first prototype is pushed to Github https://github.com/krippendorf/SDRPlayPorts 

It’s not mature code… but I first wanted to explore the API and learn how things are working in detail. PullRequest are very welcome.


Time to go from “quick and dirty” to “clean and tidy”

Invested much time exploring the FlexLib API the past days… but well invested time 🙂
Understood the concept of the radio… learned a lot about audio encoding, IQ etc. Now learning phase will lead me to a work phase to implement things clean and tidy instead of quick and dirty 🙂


Contact HB9FXQ!