Data Logger Shield and BMP085 sensor

[powersoft]

Hello,

I using for the barometric pressure measurement a BMP085 sensor (3.3 volt)
The data logger is using the I2C bus on 5.0 volt.

Can I connect this BMP085 to the other analog ports?
Or how to avoid this power problem?

Thanks for any help.

Jan Kromhout
Hellevoetsluis-NL

[adafruit_support_bill]

The BMP085 needs 3.3v for VCC. But it can use the regular Arduino I2C bus for data.

[powersoft]

This is strange. In the bmp85 sensor tutorial you write

Dont use a 5V powered I2C device (like the DS1307) at the same time as a 3.3V device like the BMP085

What to do now?

Thanks in advance

Jan Kromhout
Hellevoetsluis-NL

[adafruit_support_bill]

Yes, the DS1307 could be a problem.

There is a new SoftI2C library that will allow you to do i2c on any two pins: http://forums.adafruit.com/viewtopic.php?f=25&t=13722

[adafruit]

just remove the two 2.2K resistors from the shield.

[petermao]

Hi Jan,

have you got yours working yet? I'm trying to do the exact same thing with the adafruit data logging shield, the BMP085 pressure sensor and an LCD shield.

Here's where I am as of today:
1. grabbed the i2cv2 library
2. wired up the BMP085 SCL to analog 3 (pin 17) and SDA to analog 2 (pin 16)
3. tweaked the i2cScopeTest example to communicate software i2c w/ the BMP085 while using the HW i2c to write output to the LCD screen.

so far, I've only confirmed that something is happening on the analog 2 and analog 3 pins with a scope, I'm not processing the BMP085 data yet.

I imagine that Adafruit_BMP085.cpp needs to be reworked to read/write over the software i2c pins. has anyone done that already? or is there a slick OOP way to do it?

Peter

[petermao]

HEY!!! I got it working!

there were quite a few detail.
1. I altered the Adafruit BMP085 library to work with the I2cMaster library (see last post).
2. The I2c addresses of devices over the I2cMaster are left shifted by one bit wrt the "normal" address (0x77 turns into 0xEE).
3. I2cMaster is a little different from Wire for I2c communications. It uses the low bit of the address (recall that it has been left-shifted one bit) as a read/write bit, so there is no equivalent call to "requestFrom"

What's the best way to feed the code back upstream?

Peter

[adafruit_support_bill]

The best way to feed back on library issues is to log an issue on github.

[petermao]

I forked the Adafruit BMP085 library to run on other pins. See here.