Hi therefolks,
where can I find the wire.h library -
the reason is that I wish to use the sda and scl pins port (pins 27 and 28 on UNO R3).
I have two devices, one using a4 and a5 and I want to use the second device on the second i2c port.
appreciate any help.
J
If I'm right the Wire.h library is standard in the Arduino libraries folder.
You can include the Library in your code by doing
#include <Wire.h>
Is this your question? The library itself you can find in the Arduino folder where you installed it.
akatchi:
The library itself you can find in the Arduino folder where you installed it.
Not quite. I asked the exact same question recently, and it turns out Wire.h is here:
[Arduino install]\hardware\arduino\avr\libraries\Wire
But yep, just #include it as normal.
But @OP that's not how I2C works... it's a bus, you can have loads of devices on the sda and scl pins. I just use 2 lines of connected holes on a breadboard: take a wire from each of sda and scl to those lines, then connect the devices into those rows.
(It's similar to using the power rails on the side of breadboard.)
An Uno does mot have pins 27 and 28. 14 digital pins and 6.analog pins.
But as said, I2C is a bus system. Any reason why you need a second bus?
Hi folks, thanks for the answers.
For sterretje, if you refer to the definitive Arduino pinout diagram you will see that on the UNO V3, board with white underside, it is physical pins 27 and 28 which have the second i2c bus.
However, this brings me to another query. When I looked again at the pinout dia. surprise, surprise, why does the dia also refer to ADC5 and ADC4 on the second set of ports? I will have to post a question. Are these pins linked on the board? On the site where I bought the Arduino, they sell several different UNO's. It clearly states that the i2C is a second bus on the R3 version. Now I am not so sure.
Ah, is that what you mean by 27 and 28.
And yes, SDA and SCL are the same pins as A4 and A5 and connected on the board. So no second I2C bus for you 
Hi folks, thanks for the answers, I checked the second set of pin outs with a sensor and as sterretje has confirmed, they are linked on the board. So there is no need for me to work on the wire.h library.