I have the Arduino Pro Mini 328 5V model and the BMP085 air pressure sensor on sparkfun’s breakout board. I’m powering the BMP085 with a 3.3V regulator, and i’m pretty sure the breakout board has built in pull-up resistors. I’ve used the example sketch on sparkfun, and I’ve tried someone else’s sketch which was used specifically on the 5V pro mini. When i turn on the arduino, there is no output in the serial monitor. the code uploads fine, and i even put a line of code to print “test” in the “void setup()” section of the code, and “test” is displayed like it should be. When i put my scope on the SDA and SCL lines, i read a constant high, even if i reset my arduino. what could be wrong? would you like any additional information? Also, i’m using pin 4 as Data and pin 5 as Clock.
Posting a trimmed version of your code might be helpful.
A link to your devices would also be helpful so I wouldn’t have to go search for it.
But, I2c is on ‘A4’ and ‘A5’ (NOT 4 and 5 on the TOP), which are the 2 pins labeled on the UNDERSIDE of the mini, you are using those right?
And even tho you are using 1 device, hopefully wired closely, arduino i2c is finicky, you may need external pullups (tho the scope seems to indicate thats not a problem).
If you external device has pullups, don’t set the ones on the arduino pins.
I switched over to A4 and A5. It works like a charm now. Thanks!motopic:
A link to your devices would also be helpful so I wouldn’t have to go search for it.But, I2c is on ‘A4’ and ‘A5’ (NOT 4 and 5 on the TOP), which are the 2 pins labeled on the UNDERSIDE of the mini, you are using those right?
And even tho you are using 1 device, hopefully wired closely, arduino i2c is finicky, you may need external pullups (tho the scope seems to indicate thats not a problem).
If you external device has pullups, don’t set the ones on the arduino pins.