Klangstrom supplies an application structure to facilitate the development of applications.

Klangstrom extends the arduino idiom ( i.e setup) + loop() ) with sound, music + event related functions ( e.g audioblock() + beat() ). Klangstrom also implements a simple abstraction layer to unify access to peripherals ( e.g data_receive() + data_transmit() ).

the following functions can ( but do not have to be ) implemented in the application:

  • setup() called once at application start.
  • loop() called perpetually after setup is completed.
  • audioblock() called whenever the underlying audiosystem requires a new block of samples.
  • beat() perpetually called at a specific frequency.
  • data_receive() called when data is received from a sender.
  • event_receive() called when an event is received.

the following functions allow to configure and query application and hardware states or communicate with peripherals ( e.g LEDs, buttons, GPIOs, UART(serial), SPI, I2C, SD Card ):

in this examples a tone is played and changed periodically while an LED is turned on and off. in the setup() function two nodes are connected and the beat function is configured to be called once a second. the loop() function is implemented but does not contain any real functionality. in the beat() function LED and tone are changed every odd beat to one state and every even beat to another. in audioblock() the left and right output buffers are populated by the DAC node.

#include "Nodes.hpp"

using namespace klang;
using namespace klangstrom;

NodeVCOFunction mVCO;
NodeDAC         mDAC;

void setup() {
    Klang::connect(mVCO, Node::CH_OUT_SIGNAL, mDAC, NodeDAC::CH_IN_SIGNAL_LEFT);

void loop() {
    delay(10);                    // wait for 0.01 sec

void beat(uint32_t pBeat) {
    if ( (pBeat%2)==0 ) {
        led(LED_00, true);        // turn LED_00 on ( `true` is ON )
        mVCO.set_amplitude(0.25); // set amplitude to 25%
        mVCO.set_frequency(110);  // set frequencey to 110Hz
    } else {
        led(LED_00, false);       // turn LED_00 off ( `false` is OFF )
        mVCO.set_amplitude(0.0);  // set amplitude to 0%
        mVCO.set_frequency(200);  // set frequencey to 220Hz

void audioblock(SIGNAL_TYPE* pOutputLeft, SIGNAL_TYPE* pOutputRight, 
                SIGNAL_TYPE* pInputLeft,  SIGNAL_TYPE* pInputRight) {
    /* process next audio block */
    mDAC.process_frame(pOutputLeft, pOutputRight); 

see Klang documentation for further details on nodes.