ALL THE I2C BUSSES

[Jason Thorpe <thorpej%me.com@localhost>]

Forgive me, folks, I’m a little new to the Raspberry Pi (a little slow on the uptake, I guess :-)…

I’m a little confused about how to map the prevailing documentation on the RPI and it’s Broadcom SoC to NetBSD’s treatment of the device tree.  NetBSD shows 3 i2c controllers (iic0, iic1, iic2).  I also know the 40-pin Pi models with newer firmware have a dedicated ID EERPOM i2c bus brought out to pins 27 and 28.  All of the pinout diagrams I’ve seen show the i2c that’s on pins 3 and 5 as SDA1 / SCL1.  I always assumed that the first i2c bus wasn’t brought out to the 40-pin header, but rather used on-board only.

So, I figured that the i2c on the header would be “iic1”, reinforced by the RPI kernel config file’s dsrtc* entry.

Well, much to my chagrin, dsrtc0 was not, in fact, found on iic1.  i2cscan found them on iic2.  I can fix the kernel config file, no big deal.  But I’d like to understand the device unit mapping at play.

Thx.

nixie-dev$ sudo i2cscan /dev/iic0
Password: 
/dev/iic0: no devices found
nixie-dev$ sudo i2cscan /dev/iic1
/dev/iic1: no devices found
nixie-dev$ sudo i2cscan /dev/iic2
/dev/iic2: found device at 0x39
/dev/iic2: found device at 0x68
/dev/iic2: 2 devices found
nixie-dev$ 

-- thorpej