Digital/digital-output/render.cpp

Blinking an LED

This sketch shows the simplest case of digital out.

• Connect an LED in series with a 470ohm resistor between digital pin gOutputPin and ground.

The led is blinked on and off by setting the digital pin 1 and 0 every `gInterval seconds.

In setup() the pin mode must be set to output mode via pinMode(). For example: pinMode(context, 0, gOutputPin, OUTPUT). In render() the output of the digital pins is set by digitalWrite(). For example: digitalWrite(context, n, gOutputPin, status) where status can be equal to either 1 or 0. When set 1 the pin will give 3.3V, when set to 0 0V.

To keep track of elapsed time we have a sample counter count. When the count reaches a certain limit it switches state to either 1 or 0 depending on its current value. In this case the limit is context->digitalSampleRate * gInterval which is the desired interval expressed in samples.

/*
 ____  _____ _        _
| __ )| ____| |      / \
|  _ \|  _| | |     / _ \
| |_) | |___| |___ / ___ \
|____/|_____|_____/_/   \_\
http://bela.io
*/
#include <Bela.h>
 
int gOutputPin = 0; // digital pin 0 - check the pin diagram in the IDE
float gInterval = 0.5; // how often to toggle the LED (in seconds)
int gCount = 0; //counts elapsed samples
bool gStatus = false;
 
bool setup(BelaContext *context, void *userData)
{
    pinMode(context, 0, gOutputPin, OUTPUT); // Set gOutputPin as output
        return true;
}
 
void render(BelaContext *context, void *userData)
{
        for(unsigned int n = 0; n < context->digitalFrames; ++n){
                if(gCount == (int)(context->digitalSampleRate * gInterval)){ //if enough samples have elapsed
                        gCount = 0; //reset the counter
                        //toggle the status
                        if(gStatus == 0)
                                gStatus = 1;
                        else
                                gStatus = 0;
                        digitalWrite(context, n, gOutputPin, gStatus); //write the status to the LED (gOutputPin)
                }
                gCount++;
        }
}
 
void cleanup(BelaContext *context, void *userData)
{
        // Nothing to do here
}