Raspberry Pi & i2c bus

[Dave Tyson <dtyson%anduin.org.uk@localhost>]

Very impressed with progress so on the Raspberry Pi so I though I would try 
some more challenging tests :-)

I have been trying to couple up a BMP085 pressure sensor to the I2C bus on the 
RPI. I have tested it under raspian and it seems to work OK, but I am having a 
few issues with NetBSD (latest kernel 6.99.16 compiled yesterday)

First problem is i2cscan reports rather more devices on the bus than actually 
exist:

 /usr/sbin/i2cscan /dev/iic0
/dev/iic0: found device at 0x09
/dev/iic0: found device at 0x0a
/dev/iic0: found device at 0x0b
/dev/iic0: found device at 0x0d
/dev/iic0: found device at 0x0e
/dev/iic0: found device at 0x0f
...
/dev/iic0: found device at 0x71
/dev/iic0: found device at 0x72
/dev/iic0: found device at 0x73
/dev/iic0: found device at 0x74
/dev/iic0: found device at 0x75
/dev/iic0: found device at 0x76
/dev/iic0: found device at 0x77
/dev/iic0: 80 devices found

The same thing happens on /dev/iic1 which has nothing attached...

The BMP085 transducer is hard wired at addr 0x77 and under raspian that's all 
that is reported on iic0. C code to read the device just failed EIO, so I 
simplified it to just try and read just the top byte of the first calibration 
register. That failed EIO. Turning on debugging in bcm2835_bsc.c showed that 
the actual error was CLKT and the slave is clock stretching longer that 
specified. 

The 9 pages of publically available Broadcom documentation on this part of the 
BSC controller is a complete joke. Has anyone had any success with devices on 
this bus? Is there any more sensible documentation with maybe some state 
diagrams or timing :-)

Dave  

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