annotate projects/analogDigitalDemo/render.cpp @ 269:ac8eb07afcf5

Oxygen text added to each render.cpp file for the default projects. Text includes project explanation from Wiki, edited in places.

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/*
 ____  _____ _        _    
| __ )| ____| |      / \   
|  _ \|  _| | |     / _ \  
| |_) | |___| |___ / ___ \ 
|____/|_____|_____/_/   \_\.io

 */

/*
 *
 * Andrew McPherson and Victor Zappi
 * Queen Mary, University of London
 */

/**
\example 3_analogDigitalDemo

Analog digital workout
----------------------

This sketch showcases many different ways to write and read digital pins, 
including generating clocks and creating binary counters.

The code as it is will not work properly, as the direction of the pins is not 
set. As an exercise, you will need to set the pin mode before writing or reading 
the digital pins. 

This is for advanced users only.

*/

#include <BeagleRT.h>
#include <Utilities.h>
#include <cmath>
#include <rtdk.h>

// setup() is called once before the audio rendering starts.
// Use it to perform any initialisation and allocation which is dependent
// on the period size or sample rate.
//
// userData holds an opaque pointer to a data structure that was passed
// in from the call to initAudio().
//
// Return true on success; returning false halts the program.

bool setup(BeagleRTContext *context, void *userData)
{
	return true;
}

// render() is called regularly at the highest priority by the audio engine.
// Input and output are given from the audio hardware and the other
// ADCs and DACs (if available). If only audio is available, numAnalogFrames
// will be 0.

void render(BeagleRTContext *context, void *userData)
/*
we assume that gNumAnalogChannels=8, numAnalogFrames==8 and  numDigitalFrames==numAudioFrames
 * */
{
  /*
  * TODO: as an exercise, you will need to set the pin mode before writing or reading the digital pins.
  */
	if((context->audioSampleCount&31)==0){ //every 32 frames...
        //ANALOG channels
		analogWriteFrame(context, 0, 0, analogReadFrame(context, 0,0));
		// read the input0 at frame0  and write it to output0 frame0. Using analogWrite will fill the rest of the buffer with the same value
                                            // The value at the last frame will persist through the successive buffers until is set again.
                                            // This effectively is a pass-through with downsampling by 32 times
        analogWriteFrame(context, 0, 3, 1.0);  // write 1.0 to channel3 from frame0 to the end of the buffer
        analogWriteFrame(context, 4, 3, 0.1);  // write 0.1  to channel3 from frame4 to the end of the buffer
        analogWriteFrameOnce(context, 6, 3, 0.2); //write 0.2 to channel3 only on frame 6
        //this buffer for channel 3 will look like this:  1 1 1 1 0.1 0.1 0.2 0.1 
        //the next buffers for channel 3 will be filled up with 0.1 ....
        //DIGITAL channels
        digitalWriteFrame(context, 0, P8_07, GPIO_HIGH); //sets all the frames  to HIGH for channel 0
        digitalWriteFrameOnce(context, 4, P8_07, GPIO_LOW); //only frame 4 will be LOW  for channel 0
        // in this buffer the frames of channel 0 will look like this: 1 1 1 1 0 1 1 1 ...... 1 
        // in the next buffer each frame of channel 0 will be initialized to 1 (the last value of this buffer)
        digitalWriteFrame(context, 0, P8_08, GPIO_HIGH);
        digitalWriteFrame(context, 2, P8_08, GPIO_LOW);
        digitalWriteFrame(context, 4, P8_08, GPIO_HIGH);
        digitalWriteFrame(context, 5, P8_08, GPIO_LOW);
        pinModeFrame(context, 0, P9_16, GPIO_INPUT); // set channel 10 to input
        // in this buffer the frames of channel 1 will look like this: 1 1 0 0 1 0 0 0 .... 0
        // in the next buffer each frame of channel 1 will be initialized to 0 (the last value of this buffer)
	}
	for(unsigned int n=0; n<context->audioFrames; n++){
		for(unsigned int c=0; c<context->audioChannels; c++){
			context->audioOut[n*context->audioChannels + c]=context->audioIn[n*context->audioChannels + c];
		}
        //use digital channels 2-8 to create a 7 bit binary counter
        context->digital[n]=context->digital[n] & (~0b111111100); // set to zero (GPIO_OUTPUT) the bits in the lower word
        context->digital[n]=context->digital[n] & ((~0b111111100<<16) | 0xffff ); //initialize to zero the bits in the higher word (output value)
        context->digital[n]=context->digital[n] | ( ((context->audioSampleCount&0b1111111)<<(16+2)) ) ;  // set the bits in the higher word to the desired output value, keeping the lower word unchanged
        digitalWriteFrame(context, n, P8_29, digitalReadFrame(context, n, P8_30)); // echo the input from from channel 15 to channel 14
        digitalWriteFrame(context, n, P8_28, digitalReadFrame(context, n, P9_16)); // echo the input from from channel 10 to channel 13
        pinModeFrame(context, 0, P8_30, 0); //set channel 15 to input
	}

	for(unsigned int n=0; n<context->analogFrames; n++){
    	analogWriteFrame(context, n, 1, (context->audioSampleCount&8191)/8192.0); // writes a single frame. channel 1 is a ramp that follows gCountFrames
    	analogWriteFrame(context, n, 2, analogReadFrame(context, n, 2)); // writes a single frame. channel2 is just a passthrough
//		rt_printf("Analog out frame %d :",n);
//		for(int c=0; c<gNumAnalogChannels; c++)
//			rt_printf("%.1f ",analogOut[n*gNumAnalogChannels + c]);
//		rt_printf("\n");
	}
	return;

}

// cleanup() is called once at the end, after the audio has stopped.
// Release any resources that were allocated in setup().

void cleanup(BeagleRTContext *context, void *userData)
{
	// Nothing to do here
}