I spent some time trying to hook an i2c device to the i2c1 pins - (17,18) on the P9 expansion connector.
It failed most completely to work - I hooked my device up to i2c2 pins (19,20) on P9 and everything is dandy.
Then I de-compiled (un-compiled?) anyway I pulled the dtb for BBB in the boot directory and ran it thought the dtc compiler backwards. I did that because when I looked at the source which I was pretty sure my build was picking up I saw
pinmux_i2c0_pins {
pinctrl-single,pins = <0x188 0x70 0x18c 0x70>;
linux,phandle = <0x6>;
phandle = <0x6>;
};
pinmux_i2c2_pins {
pinctrl-single,pins = <0x178 0x73 0x17c 0x73>;
linux,phandle = <0x7>;
phandle = <0x7>;
};
So in fact i2c1 is not being configured in the device tree. Is there a reason for this?
But that’s beside the point - my familiarity to device trees is limited and I was trying to figure out where all the magic numbers come from.
On line pinctrl-single.pins = <0x188 0x70 0x18c 0x70> ;
Ive figured out that the 0 in 0x70 is the gpio pin mode .
This is however very painful - and not at all what I would expect from a “better” initialization method. Can someone point me to documentation that will let me know how to configure i2c1 and/or other bits and pieces on this board?
It would be great to be able to configure one of the gpio pins as an interrupt source.
BTW - phandle ??? SERIOUSLY??? Since when did Linux start using reverse Hungarian? - even Microsoft has done away with it.
…JW