7 Replies Latest reply on Apr 1, 2013 5:01 PM by Problemchild

How to use Ardunio to listen on i2c bus mastered by 2nd Arduino?

allen13331 Dec 1, 2012 1:22 PM

I have just competed an i2c project running (8) DS18B20 all over the house which displays the results on a 20x4 LCD. I would like to monitor the i2c results at additional locations. Is is possible to set the Ardunino to listen to the i2c line and report the results, without conflict? I am new to all this (not an EE or C programmer and 60 years old), and just starting this hobby as a newbie so it seems simple which means it is not. Can I use the i2c sketch that I use for the DS 18B20 and modify it to just listen? Any help would be appreciated.

Thanks.

Allen

Re: How to use Ardunio to listen on i2c bus mastered by 2nd Arduino?

dmaruska Dec 1, 2012 2:59 PM (in response to allen13331)

Hi. nxp has a i2c multiplexer chip. you can break the bus and communicate with each as you need .
Like (0)

Reply

Actions
- Re: How to use Ardunio to listen on i2c bus mastered by 2nd Arduino?
  
  Andy Clark (Workshopshed) Dec 4, 2012 8:55 AM (in response to dmaruska)
  
  Here's an example where the Arduino listens on an I2C bus.
  
  http://rascalmicro.com/docs/basic-tutorial-controlling-motors.html
  
  However, reading a couple of articles suggests that each slave on the bus is required to tell the master it's address, so that's not going to work for your case.
  
  So you need to be a bit more cunning.... luckily, someone else has already done this. Johngineer has written an I2C Sniffer that reports the data from the bus back to the serial port.
  
  http://www.johngineer.com/blog/?p=455
  
  Here's another interesting sketch that scans the bus for different devices which would be useful if you did not know the address of the item you were looking at
  
  http://arduino.cc/playground/Main/I2cScanner
  
  Like (0)
  
  Reply
  
  Actions
  - Re: How to use Ardunio to listen on i2c bus mastered by 2nd Arduino?
    
    allen13331 Dec 4, 2012 10:28 PM (in response to Andy Clark (Workshopshed))
    
    Thanks, that gives me some ideas to work on. It seems like it should be so simple but I am learning that nothing is simple...of course if it was not a challenge I would not be interested in doing it.
    
    Thanks.
    
    Like (0)
    
    Reply
    
    Actions
    - Re: How to use Ardunio to listen on i2c bus mastered by 2nd Arduino?
      
      Andy Clark (Workshopshed) Dec 5, 2012 2:00 AM (in response to allen13331)
      
      One more thought I just had, you could put the 2nd arduino in the middle with 2 I2C connections, it could then echo the data from the master to the slave and vice versa.
      
      Like (0)
      
      Reply
      
      Actions
      - Re: How to use Ardunio to listen on i2c bus mastered by 2nd Arduino?
        
        allen13331 Dec 5, 2012 8:41 AM (in response to Andy Clark (Workshopshed))
        
        Thanks for the idea, seems like I should be able to get something to work. As a newbie the i2c buss is really fun to work with. The DS 18b20 is so easy to work with and deploy. I wish I knew how to find more sensors that would work with the same librar, so I could get some different kinds of data other than just temperature. Any ideas on that one? We travel a lot and I monitor the house remotely while we are gone to spot potential problems, or developing problems.
        
        Thanks again
        Allen
        
        Like (0)
        
        Reply
        
        Actions
        
        Re: How to use Ardunio to listen on i2c bus mastered by 2nd Arduino?
        
        Andy Clark (Workshopshed) Dec 6, 2012 3:12 AM (in response to allen13331)
        
        One sensor I've been looking at is the DHT22 which is temperator+humidity also there are a few places selling barometric pressure sensors such as the MPL115A1MPL115A1
        However those are both likely to need different libraries to the DS18b20.
        
        Like (0)
        
        Reply
        
        Actions
        
        Re: How to use Ardunio to listen on i2c bus mastered by 2nd Arduino?
        
        Problemchild Apr 1, 2013 5:01 PM (in response to Andy Clark (Workshopshed))
        
        Mind you the DHT22 is some wierd single pin protocol much the same as the DHT11 it's worth trying the DHT11 lib for this sensor.
        In fact the DHT22 seems to be an excellent sensor much more accurate than the DHT11
        
        The Arduino Lib is here so well supported
        
        Like (0)
        
        Reply
        
        Actions