I've recently started experimenting with a new arduino uno. I have spent many hours trying to establish a connection with I2C chips, but without success. I have worked with an LM75 temperature sensor and a 24lc256 eeprom, using different code examples found on the net. It seems that the arduino board is unable to establish any communication with the I2C chips. The hardware setup is ok, I've checked it over and over again and I have tested it successfully with another microcontroller. I have tried with and without pullup resistors. The arduino always behaves as if there was no I2C chip connected at all.
Also the address of the chips was checked and tested many times, I have also tried to run the sketch scanning the I2C bus (I2CScanner.pde found on Index of /arduino/sketches/I2CScanner) which should be able to detect any connected device.
So I thought that maybe the ATmega328 had a defect and I replaced it with a new one. It didn't solve the problem. Is it possible that the Uno board has a fault?
Can anybody recommend any further testing procedure? Thanks.
Somehow I think you have it connected up wrong...
What pins and how?
Is it possible that the Uno board has a fault?
Not really - well not just for i2c.
Mowcius
As described in various posts i have connected
SDA to Arduino 4
SCL to Arduino 5
WP goes to ground
Vcc goes to arduino 5V
Vss goes to ground
A2, A1, A0 to ground
To be sure I have also tested inverting pins 4 and 5.
The strange thing is that the same configuration connected to another microcontroller works fine
Hmm, have you checked the continuity between the pins on the chip and the pins on the board?
Mowcius
Yes, checked and re-checked.
I was thinking that perhaps the oscillator might not work at the correct speed. Could that affect i2C communication?
SDA to Arduino 4
SCL to Arduino 5
You're using Analog 4 & 5 not Digital 4 & 5 right?
hmmm, not so sure, I have to check that again... maybe I used the digital ones....thanks!
Problem solved! Yes, I was using the digital pins. It seemed so obvious to me that it had to be the digital pins that it never occurred to me that it could be the analog ones. Thanks for your help!!!
Glad to hear it