0
\$\begingroup\$

I am pondering about interfacing with the iPad Mini 2 touch panel. It seems that no one has successfully done this and/or published anything about it, so I want to take a stab at it.

As far as I understand the device uses a custom touch screen controller IC, meaning I can't get a datasheet for it. Luckily someone at least made a schematic for the device and we can see that the controller seems to talk to the uC through SPI.

iPad Mini 2 Touch Panel Connector

Given that I don't know the protocol for the IC would there be some way to find out the protocol by spamming the input and seeing what comes out of the output?

Thank you!

\$\endgroup\$
1
  • 1
    \$\begingroup\$ In keeping with yesterday's theme, you might be wanting t' get a bus Pirate to sniff the lines. Not expensive. \$\endgroup\$
    – Spehro Pefhany
    Sep 20, 2017 at 17:00

1 Answer 1

Reset to default
2
\$\begingroup\$

I don't think you'll be able to get anywhere by just addressing registers at the input and seeing what comes out. For one, this doesn't answer how you are supposed to initialize the controller, which is vital to using the part. That's also a lot of data to analyze.

You'll probably get a lot farther by sniffing the SPI lines of the touch panel in situ. Mechanically it may be challenging to get probes on those lines while it's connected to the rest of the iPad, but electrically it's worth it.

Probe all four lines and record commands on startup (filter out anything where CSL is high). That'll show you how the uC initializes the controller, as well as the clock frequency. Next you can just look for patterns in the commands during operation and you should be able to figure out what registers it's polling to get touch info. This will be 1000% easier with a scope or logic analyzer that can decode and record SPI, because you can just export the list of commands to an excel doc and work from there.

\$\endgroup\$
2
  • \$\begingroup\$ Yep, I expected this to be the case. The drawback being that I'll actually have to get a full iPad to do this. As for getting probes on the lines I think I can do a little in-between breakout board with the connector. Thanks. \$\endgroup\$
    – carlossless
    Sep 20, 2017 at 12:45
  • \$\begingroup\$ That was my practical answer but knowing some of the people on here you might get a much more creative solution, keep your fingers crossed! \$\endgroup\$
    – jalalipop
    Sep 20, 2017 at 12:48

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.