I2C via other available Pins

Forum 2005-2010 (read only) Hardware Interfacing
1

hi,

I understand that the current "Wire" library sets Port C4 and Port C5 for I2C. Is there a way to set other ports as I2C comms? Thanks in advance!

2

I dont think you can do that.

3

There are libraries that bit-bang I2C communication on other pins. For example, the JeeLabs "Ports" library: http://cafe.jeelabs.net/sw/library_-_ports/

4

I2C is hardwired into the AtMega168 and 328 to use those pins. See the pin mapping diagram http://arduino.cc/en/Hacking/PinMapping168 for the functions available from these chips to show how they map to the Arduino pin layout. Port C4 = AD4/SDA and Port C5 = AD5/SCL.

Jee Labs has done work on an Arduino variant and uses software I2C to extend the number of I2C capable pins here http://news.jeelabs.org/2010/03/15/software-and-hardware-i2c/ and I think this http://cafe.jeelabs.net/sw/library_-_ports/ is the library that allows the JeeNode to do this. Instructions are given for adding it to the Arduino IDE.

5

hi Professor Chaos and capt.tagon,

Thanks alot! It's exactly what I'm looking for, bit-bang I2C.

6

Wait.. so can you redirect I2C to other digital pins and then use Analog_4 and Analog_5 as regular analog pins to measure voltages? Or would Analog_4 and Analog_5 still be hogtied by I2C?

7

If you bit banged the I2C and didn't use the internal I2C hardware then yes you could reclaim those two analogue inputs.

8

Just find "SoftI2CMaster.h" and its associated c - it works well.

#include <SoftI2cMaster.h>
#define SCL_PIN 9
#define SDA_PIN 8
SoftI2cMaster rtc;
#define DS1307ADDR 0XD0