andrewm@0: /*
robert@269:  ____  _____ _        _    
robert@269: | __ )| ____| |      / \   
robert@269: |  _ \|  _| | |     / _ \  
robert@269: | |_) | |___| |___ / ___ \ 
robert@269: |____/|_____|_____/_/   \_\.io
robert@269: 
robert@269:  */
robert@269: 
robert@269: /*
andrewm@0:  *
robert@269:  * Andrew McPherson and Victor Zappi
robert@269:  * Queen Mary, University of London
andrewm@0:  */
andrewm@0: 
robert@269: /**
robert@269: \example 3_analog_output
robert@269: 
robert@269: Fading LEDs
robert@269: -----------
robert@269: 
robert@269: This sketch uses a sine wave to drive the brightness of a series of LEDs 
robert@269: connected to the eight analog out pins. Again you can see the nested `for` loop 
robert@269: structure but this time for the analog output channels rather than the audio.
robert@269: 
robert@269: Within the first `for` loop in render we cycle through each frame in the analog 
robert@269: output matrix. At each frame we then cycle through the analog output channels 
robert@269: with another `for` loop and set the output voltage according to the phase of a 
robert@269: sine tone that acts as an LFO. The analog output pins can provide a voltage of 
robert@269: ~4.092V.
robert@269: 
robert@269: The output on each pin is set with `analogWriteFrame` within the `for` loop that 
robert@269: cycles through the analog output channels. This needs to be provided with 
robert@269: arguments as follows `analogWriteFrame(context, n, channel, out)`. Channel is 
robert@269: where the you give the address of the analog output pin (in this case we cycle 
robert@269: through each pin address in the for loop), out is the variable that holds the 
robert@269: desired output (in this case set by the sine wave).
robert@269: 
robert@269: Notice that the phase of the brightness cycle for each led is different. This 
robert@269: is achieved by updating a variable that stores a relative phase value. This 
robert@269: variable is advanced by pi/4 (1/8 of a full rotation) for each channel giving 
robert@269: each of the eight LEDs a different phase.
robert@269: 
robert@269: */
robert@269: 
andrewm@0: 
andrewm@56: #include <BeagleRT.h>
andrewm@56: #include <Utilities.h>
andrewm@0: #include <rtdk.h>
andrewm@0: #include <cmath>
andrewm@0: 
andrewm@0: // Set range for analog outputs designed for driving LEDs
andrewm@52: const float kMinimumAmplitude = (1.5 / 5.0);
andrewm@52: const float kAmplitudeRange = 1.0 - kMinimumAmplitude;
andrewm@0: 
andrewm@0: float gFrequency;
andrewm@0: float gPhase;
andrewm@0: float gInverseSampleRate;
andrewm@0: 
andrewm@56: // setup() is called once before the audio rendering starts.
andrewm@0: // Use it to perform any initialisation and allocation which is dependent
andrewm@0: // on the period size or sample rate.
andrewm@0: //
andrewm@0: // userData holds an opaque pointer to a data structure that was passed
andrewm@0: // in from the call to initAudio().
andrewm@0: //
andrewm@0: // Return true on success; returning false halts the program.
andrewm@0: 
andrewm@56: bool setup(BeagleRTContext *context, void *userData)
andrewm@0: {
andrewm@0: 	// Retrieve a parameter passed in from the initAudio() call
andrewm@0: 	gFrequency = *(float *)userData;
andrewm@0: 
andrewm@52: 	if(context->analogFrames == 0) {
andrewm@12: 		rt_printf("Error: this example needs the matrix enabled\n");
andrewm@0: 		return false;
andrewm@0: 	}
andrewm@0: 
andrewm@52: 	gInverseSampleRate = 1.0 / context->analogSampleRate;
andrewm@0: 	gPhase = 0.0;
andrewm@0: 
andrewm@0: 	return true;
andrewm@0: }
andrewm@0: 
andrewm@0: // render() is called regularly at the highest priority by the audio engine.
andrewm@0: // Input and output are given from the audio hardware and the other
andrewm@0: // ADCs and DACs (if available). If only audio is available, numMatrixFrames
andrewm@0: // will be 0.
andrewm@0: 
andrewm@52: void render(BeagleRTContext *context, void *userData)
andrewm@0: {
andrewm@56: 	for(unsigned int n = 0; n < context->analogFrames; n++) {
andrewm@0: 		// Set LED to different phase for each matrix channel
andrewm@0: 		float relativePhase = 0.0;
andrewm@56: 		for(unsigned int channel = 0; channel < context->analogChannels; channel++) {
andrewm@0: 			float out = kMinimumAmplitude + kAmplitudeRange * 0.5f * (1.0f + sinf(gPhase + relativePhase));
andrewm@0: 
andrewm@52: 			analogWriteFrame(context, n, channel, out);
andrewm@0: 
andrewm@0: 			// Advance by pi/4 (1/8 of a full rotation) for each channel
andrewm@0: 			relativePhase += M_PI * 0.25;
andrewm@0: 		}
andrewm@0: 
andrewm@0: 		gPhase += 2.0 * M_PI * gFrequency * gInverseSampleRate;
andrewm@0: 		if(gPhase > 2.0 * M_PI)
andrewm@0: 			gPhase -= 2.0 * M_PI;
andrewm@0: 	}
andrewm@0: }
andrewm@0: 
andrewm@56: // cleanup() is called once at the end, after the audio has stopped.
andrewm@56: // Release any resources that were allocated in setup().
andrewm@0: 
andrewm@56: void cleanup(BeagleRTContext *context, void *userData)
andrewm@0: {
andrewm@0: 
andrewm@0: }