Teensy 3.1 Impressions and the Audio Library

I have been hearing a lot of good things about the Teensy 3.1 development board regarding its use as a SDR platform HERE. It seems like it has a great deal of capability over the the Teensy 2.0 that I have been using. This power is due to it's 32 bit ARM processor. The coolest thing is that it uses the Arduino IDE and nearly all of your sketches will run on it. The Teensy SDR linked above exploits the Teensy 3.1 audio DSP functions and PJRC has created a simple GUI tool to help you create your audio projects easily.

As a simple test after I powered up my Teensy 3.1, I used the audio design tool to define two sine wave sources, mix them together and output them to the on-board DAC. Below is an image of my session with the tool (it is web based or you can download and run locally).

After the design is completed in the tool you just press the RED "Export" button and it will output the code for your sketch. I ended up tailoring mine to generate a Dial Tone and I was blown away how good it sounded! I just took the output of the DAC and feed it directly into a standard PC powered speaker.

You do need to do a little coding since the tool just sets up the streams. The tool generated the code that is between the "// GUItool ..." comments below in the example. I needed to call the audio objects in the "loop()" section which you can figure out from the docs and the examples provided. The comment section at the bottom is when I was playing with other Tel-co sounds (e.g. Busy Signal).

I am very impressed with the Teensy 3.1 platform and intend on replacing my Teensy 2.0 in my Proto Type Radio with it soon and try out some of the audio SDR functions.

Example Code:

 // Simple Mixer to generate a Dialtone  
 #include <Audio.h>  
 #include <Wire.h>  
 #include <SPI.h>  
 #include <SD.h>  
 // GUItool: begin automatically generated code  
 AudioSynthWaveformSine  sine1;     //xy=183,181  
 AudioSynthWaveformSine  sine2;     //xy=192,251  
 AudioMixer4       mixer1;     //xy=392,207  
 AudioOutputAnalog    dac;      //xy=591,178  
 AudioConnection     patchCord1(sine1, 0, mixer1, 0);  
 AudioConnection     patchCord2(sine2, 0, mixer1, 1);  
 AudioConnection     patchCord3(mixer1, dac);  
 // GUItool: end automatically generated code  
 void setup() {  
  // Audio connections require memory to work. For more  
  // detailed information, see the MemoryAndCpuUsage example  
  AudioMemory(3);  
  }  
  void loop() {  
  sine1.frequency(350); //350  
  sine1.amplitude(0.1);  
  sine2.frequency(440);//440  
  sine2.amplitude(0.1);  
  //delay(100);  
  //sine1.amplitude(0);  
  //sine2.amplitude(0);  
  //delay(100);  
  }