OS/2, eCS & ArcaOS - Technical > Hardware
Mouse, Trackpoint, Trackpad, Touchpad - I2C Question
Wim Brul:
Article Device Bus Connectivity (touchpad-device-bus-connectivity) discusses bus connectivity methods for a Windows Precision Touchpad device.
Lars:
Question is: how does the I2C controller interface to the PC system?
Does the I2C controller show up as a PCI device ? Is there a standardized set of (io mapped or memory mapped) registers or some such to talk to the I2C controller ?
I also cannot find any information on how to unambiguously identify a device on the I2C bus. You can scan the I2C bus and see what device addresses are in use but not exactly what device (like for USB, the vendor and product id ...).
That seems to be pretty proprietary, from what I can tell all scan code for I2C devices guesses the device by its typical address use.
Martin Iturbide:
Hello
On my T14s I have an ELAN trackpoint. Windows recognize the device as "04F3" which is the ELAN's Vendor ID.
The Testlog PCI report does not show anything with "04F3".
I guess Windows has something to query the I2C bus. But looking around everyone refers to linux's I2C Tools.
I also try to find more information, but I guess it is getting out my technical skills and getting more into the hardware world.
https://forums.freebsd.org/threads/making-i2c-elan-touchpad-work-elan0d07-00-04f3-3078-on-a3511.86749/
https://man.freebsd.org/cgi/man.cgi?query=i2c
Regards
Flashback:
--- Quote from: Martin Iturbide on November 29, 2024, 05:10:38 pm ---I guess Windows has something to query the I2C bus. But looking around everyone refers to linux's I2C Tools.
--- End quote ---
As others pointed out, devices on the I2C are not detectable. The Linux tools can only tell, if there is something responding on a given bus address, not what that is.
The usual way make undetectable devices known to an OS is to mention them in the ACPI tables or - on embedded Linux - in the device tree. Ideally, including information on how to access them. I'm pretty sure, that this is the way Windows and Linux learn about these devices.
Rich Walsh:
--- Quote from: Flashback on November 30, 2024, 11:18:24 am ---The usual way make undetectable devices known to an OS is to mention them in the ACPI tables
--- End quote ---
'testlog acpi' should give you everything you need to find out - its just a matter of figuring out what it means :)
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