Re: i2c and indirect vs. direct config

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

> On May 30, 2018, at 11:54 AM, Brad Spencer <brad%anduin.eldar.org@localhost> wrote:

> Does the techniques mentioned in these offer any hope of determining the
> presence of an actual device at a particular address on the bus in a
> harmless manor:
> 
> http://forum.arduino.cc/index.php?topic=61520.0
> https://electronics.stackexchange.com/questions/76617/determining-i2c-address-without-datasheet
> 
> The second, in particular, simply does a start+address+stop.. if the
> response to the address was ACK there was a device, otherwise, there if
> it was a NAK there wasn't anything there.  I don't know how well this
> works in in practice.  But it would seem to be something that would not
> be able to upset a device.

That’s a great idea, actually.  It would certainly help the ghosting problem.  Perhaps we can centralize the logic into a helper function that does the START-address-STOP handshake and also filters the address against a list of valid addresses passed by the driver (in general, i2c devices can’t be at arbitrary addresses).

-- thorpej