Specifying an I2C device (Linux)

I’ve got the ArduCopter software complied and ready on a development board. However, it can’t seem to pick up my BMP180 on my I2C bus, resulting in this:

AP_Baro::read unsuccessful for more than 500ms in AP_Baro::calibrate [2]
Now I know it’s there, because I can access it with other programs and it shows up under i2cdetect:

root@intel-corei7-64:~/ardupilot/ArduCopter# i2cdetect -y -r 7 0 1 2 3 4 5 6 7 8 9 a b c d e f 00: -- -- -- -- -- -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 20: -- -- -- -- -- -- -- -- -- 29 -- -- -- -- -- -- 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 70: -- -- -- -- -- -- -- 77
However, I noticed that the device only shows up if I run i2cdetect on bus 7. I’ve got a lot of I2C devices in /dev/ as you can see:

root@intel-corei7-64:~/ardupilot/ArduCopter# ls /dev/i2c* /dev/i2c-0 /dev/i2c-2 /dev/i2c-4 /dev/i2c-6 /dev/i2c-8 /dev/i2c-1 /dev/i2c-3 /dev/i2c-5 /dev/i2c-7 /dev/i2c-9
How do I specify a bus to look for this device? I think it might be probing /dev/i2c-0 or whatever the default device is. I haven’t worked with I2C very long, but every other time I’ve seen or written code for it, a bus had to be specified. Where is that set in arduCopter’s I2C? I couldn’t find it after looking for hours.
Thanks for your help!

I’m new to this, but it could be that AP_HAL_Linux/HAL_Linux_Class.cpp is the file to look in.

It’s described on line AP_HAL_Linux/HAL_Linux_Class.cpp:39:24

i2cDriver0 is declared on /dev/i2c-1 for a Generic Linux boards.