Learning to find I2C addresses of sensors for Arduino Due

In order to program the Arduino Due microprocessor you have to have Arduino IDE 1.5 or later which can be found here:

https://www.arduino.cc/en/Main/Software#toc3

After installing Arduino 1.5 or later the link below may be able to help.

https://www.arduino.cc/en/Guide/Environment

Hi Rahim,

The Wikipedia page for I2C explains that devices are either master or slave.

The microcontroller on the Arduino Due is a master device usually. It doesn't have an I2C address. I2C addressing is for slave devices.

The usual method is to see what integrated circuits (ICs) require I2C interfacing, and then the addresses can be found in the product datasheets for those ICs. You can just type the IC part number in google to get the datasheets.

Does the Arduino Due have peripheral chips on-board that use I2C? I didn't think that was

the case, but I'm not familiar with it.

If you're interfacing an I2C device to the Arduino Due, then you need to check the datasheet of the device that you are interfacing.

Rahim;

There are a couple of excellent tutorials on tronixstuff.com specifically about using I2C and Arduino.  It looks like you've already been to Adafruit, so no need to mention that.

http://tronixstuff.com/2010/10/20/tutorial-arduino-and-the-i2c-bus/

Here is a more general one on SparkFun: https://learn.sparkfun.com/tutorials/i2c

And the I2C/Wire library reference on the Arduino site: https://www.arduino.cc/en/Reference/Wire

When you're reading, the "Two-Wire" or "TWI" protocol is I2C.  Some refer to it as Two-Wire, understandably, as connections just require two wires: SDA (Data) and SCL (Clock).  A couple of gotcha's that you may or may not be aware of.  The Due is a 3V3 uC, unlike most Arduinos, which are 5VDC.  You'll need to reference (Include) the "Wire" library in your programming.  If you're using an IDE besides Arduino (Keil, Atmel Studio, etc.) then check Atmel's website for additional libraries required.

Arduino pins can sink 20mA of sustained current, or 40mA max.  Not a problem using I2C, but if you use other pins be aware of those limitations. 

Use a 9-12VDC/2A power source on the DC jack, when not using the USB port for power.  Any lower voltage and your uC may destabilize.  Much higher and the on-board voltage regulator will get too hot.  You can't really attach a heatsink as the VR is flush-mounted on the PCB.

Best of luck!

Hello Rahim,

today later I plan to post in Arduino an article on the use of SDA/SCL (Data and Clock) with the LCD alphanumeric display, driven by a shift register. This particular case just only use the two wires of I2C without the need to manage the chip select (not available in the shift register. Will add some more detail on how the library control work in the hope it will be helpful to you.

Managing more than one device with I2C means to use always the same 2 wires (that are, the I2C bus) and addressing pin(s) to tell to the bus what is the device that should be controlled in a particular moment. I think that seeing the things in two separate steps maybe more understandable.

Enrico

Here are a bunch of Videos and Posts I have produced in the past that also use / describe I2C

The Modular Bench Power Supply ++, Arduino UNO and precision ADC, DAC + MDO3000 I2C debugging

Fuel Tank BoosterPack With Rechargeable LION Battery and CCS or Energia - I2C issues

MDO3000 used to debug I2C on an Arduino UNO using the embed option

The Modular Bench Power Supply ++, Arduino UNO and precision ADC, DAC + MDO3000 I2C debugging

What you have not said is what you want to do with the I2C, what chips are you going to communicate with or is it another Arduino ??

also there is of course hte Arduino Help pages them selves https://www.arduino.cc/en/Reference/Wire

So asside from learning the basics about what I2C is, then you need to decide what you want to do with it ?. As Shabaz has already stated, the addresses of the chips is not hard to find, you just refer to the datasheets

knowing what chip to select in the first place is a little harder but if appoached methodically should not be too hard

I.E. Google the function you want along with the connection type ("I2C ADC 8bit") will give you plenty of chips that are Analogue to Digital Converters, 8Bit resolution with an I2C communications bus

This was helpful marcus barnes.

Thank you!

Rahim M.

Thank you for your advice shabaz! Well, myself being very inexperienced with Arduino programming and the hardware itself, I really do not know that much about on-board peripheral chips. Right now, the main issue for us is learning the process of Reading and Writing from our I2C senors to our Arduino Due microprocessor, of basically setting up the code for the sensors and microprocessor to communicate.

Any advice on this would be greatly appreciated.

Thank you.

Rahim M.

Thank you Brian Edwards!!! The link to tronixstuff is really putting things into a better prospective. Right now our team is doing its best to set up code to get the I2C sensors to Read and Write to the Arduino Due one at a time, but we are running into some issues that are holding us back from even getting one sensor to work. We know that there is a issue with the code, but we can not seem to pen-point what the issue is exactly.

So far, here is the code that we put together in bits and pieces down bellow...If you or someone else can help figure out what's wrong with the code it would be very much appreciated.

Thanks again.

Rahim M.

#include <Wire.h>

void setup()

{

   Serial.begin(57600);

   Wire.begin();

}

#define MPL3115A2_ADDRESS 0x60

void loop()

{

   Serial.println(IIC_Read(0x0C));

}

z

byte IIC_Read(byte regAddr)

{

  // This function reads one byte over IIC

  Wire.beginTransmission(MPL3115A2_ADDRESS);

  Wire.write(regAddr);  // Address of CTRL_REG1

  Wire.endTransmission(false); // Send data to I2C dev with option for a repeated start. THIS IS NECESSARY and not supported before Arduino V1.0.1!

  Wire.requestFrom(MPL3115A2_ADDRESS, 1); // Request the data...

  return Wire.read();

}

uint8_t I2CReadRegister(uint8_t I2CDestinationAddress, uint8_t Register)

{

   Wire.beginTransmission(I2CDestinationAddress);

   Wire.write(Register);

   Wire.endTransmission(false);

   Wire.requestFrom(I2CDestinationAddress, 1 );

   delay(200);

   return Wire.read();

}

void I2CWriteRegister(uint8_t I2CDestinationAddress, uint8_t Register, uint8_t Data)

{

   Wire.beginTransmission(I2CDestinationAddress);

   Wire.write(Register);

   Wire.write(Data);

   Wire.endTransmission();

}

You're welcome Rahim.

First question/observation - In your code what is 'z' in your loop?

void loop()

{

   Serial.println(IIC_Read(0x0C));

}

z      // What is this referencing?

byte IIC_Read(byte regAddr)

I'm not familiar with the Arduino [so view this as trying to help, but could well be wrong], but from the Arduino reference data you point to it looks like you aren't giving it time to do the I2C transfer.

Wire.requestFrom(MPL3115A2_ADDRESS, 1); // Request the data...

That says "go and read a byte from the I2C"

You then try to read the byte immediately with

return Wire.read();

You're working on the assumption that requestFrom blocks and execution doesn't continue until the data is in the buffer but that isn't necessarily true if the I2C stuff is running on interrupts in the background.

A quick and dirty test is to try inserting a delay(200), as in the example routine, before the return and see what that does. If that works, you can then look at how to do it properly using Wire.available, which seems to be your means to find out what's in the buffer.

Putting

do() while(Wire.available() == 0);  //loop doing nothing while there are no bytes in the buffer

before the return would be one way if you don't mind wasting the 20uS or 30uS that it would sit there.

[Hope I've got that right - I'm an old hardware engineer, so no expert with coding, though I can just about cobble together bits of C when I put my mind to it.]

If none of that works, I should put a scope on it and take a look at SCL and SDA [a scope is much the best way to debug firmware when there's hardware involved].

Good luck with your weather balloon project - sounds interesting and fun.