i2cperipheral

Overview

This repo contains some arduino helper files to build applications that interface with multiple I2C sensors and handle the multi programming.

The idea is that each sensor can be set to be called at a different minimum interval allowing other tasks to complete.

It is based on the high performance I2C library by Wayne Truchsess. See http://dsscircuits.com/articles/arduino-i2c-master-library.html And you can download it at https://github.com/rambo/I2C

Another useful class is the stopwatch which allows you to track time between events without having to pepper the code with "if((msecs()-last)>interval)" and have to maintain mutiple variables.

Usage

In genral this is the format of the class:

class MyPeripheral : public I2CPeripheral
{
  public:

    MyPeripheral(int interval = SOME_DEFAULT_INTERVAL)
    {
      // This is the interval the I2C bus will be available - provided it is not being used
      // bt another peripheral
      setInterval(interval);
    }
    
      
    void setup()
    {
	// setup your peripheral here
    }

    void onUpdate()
    {
	  // When this call is made, the i2c is guaranteed to be available exclusively to this peripheral
	  // So try to do it as fast as possible! 
	  //I2c.dosomethinghere(....);

	  //Serial.print("Bus locked: ");
          //Serial.println(millis());

	  // When the I2C data aquisition is completed, it signals to the caller that new data is available
	  newDataAvailable();
      }
    }  
  private:
};

The caller can have multiple peripherals connected after the caller completes processing the data it signals the peripheral that it has processed the data:

// IN main file:

bool newDataAquired;

void loop()
{
   newDataAquired = false;
   peripheral1.update();
   if (peripheral1.hasNewData())
   {
      //do something here
      peripheral1.dataProcessed();
      newDataAquired = true;
   }

   peripheral2.update();
   if (peripheral2.hasNewData())
   {
      //do something here
      peripheral2.dataProcessed();
      newDataAquired = true;
   }

   peripheral3.update();
   if (peripheral3.hasNewData())
   {
      //do something here
      peripheral3.dataProcessed();
      newDataAquired = true;
   }

   if (newDataAquired)
   {
	// do something here like recalculate bearings
   }

   // do stuff that always need to be done
}

Improvement

A further improvement would be to create peripheral sub-classes where the new data is processed and the main loop could be de-clutterfied.

extern bool newDataAquired;

class MyHMC5883 : public HMC5883
{
	MyHMC5883() : 
	   HMC5883()
	{
		
	}

	void doUpdate()
	{
		HMC5883::doUpdate();
		if (hasNewData())
		{
			// Do something here

			// if you call next line main loop will not know about new data
			dataProcessed();
			// so we signal main loop that something changed!
			newDataAquired = true;
		}
	}
}

Notes

that this version is blocking which means that the I2C calls block while waiting for response - with the following consequences:

• One wants to minimize calls to the sensors
• Make short I2C calls

The included sensor examples are WiiMote Pixart camera and HMC5883 magnetic sensor. More sensors to come! Both can run at 400KHz fast I2c

This repo is the seed to a better shared peripheral library to be announced