I don't think I've ever seen a touch screen with only two wires. For one thing, even power requires two wires, not one. Data for a touch screen typically requires more than one wire as well, especially considering there are two completely distinct types of data a touchscreen must transmit, those being display output and touch input.
Most touch screens I'm aware of have wire connections more like this:
https://learn.adafruit.com/adafruit-2-4-color-tft-touchscree...
> Usually they're replacing a lot more than 2 buttons/knobs.
Not usually. Other than the Tesla, most cars retain almost all of their knobs/buttons in addition to the touch screen. In fact, the linked article in the OP says they're basically replacing the touch screen input with a single volume knob that lets you additional tilt and push it. Other cars, like BMW with the iDrive, usually have a single knob that lets you rotate and scroll through menus and push to select. Granted, it's not a simple knob, since it requires multiple degrees of input, but even a plastic knob that allows rotating, tilting, and pushing is probably cheaper than a touch screen when shared across models and mass produced.
I still think the bigger savings is probably the software updates required to constantly support and make your vehicle's physical input compatible with every new update of Android Auto and Apple Car Play, which the auto-makers have no control over and can only ever play catch-up. At least with a touch screen, they know that's where the Android and Apple engineers spend their own time making compatible.
The other place it probably saves is designing and laying out the interior, since it's easier to design an interior with fewer purpose-focused inputs. I'm not sure though if the touch screen would actually be easier though, since it can't be broken up across different small areas, and the entire thing has to be within both reach and active field of view. Especially the screens on top of the dash, since those often are designed to retract, which means the space they retract into needs to be designed around the HVAC and electrical systems between the firewall and dash.
Either way, both of these savings though would be on the design and engineering side, not the bill of materials.
That link is to a toy touchscreen. Are we counting every strand of metal as its own wire now? I think the power and the data cables are each bundles of lots of such strands, and no car manufacturers worry about the individual strands because each cable plugs into the circuit board as a cohesive unit, like: https://www.alibaba.com/product-detail/Customized-odm-15-6-i...
(First Google result for "touchscreen alibaba", it's not like this is an obscure, rarely used configuration.)
Either way, both of these savings though would be on the design and engineering side, not the bill of materials.
¯\_(ツ)_/¯ Those sound like good points to me, but I don't know anything about this stuff.
The chasis is your second cable.
Of course you need to get the touch screen reliable. A touch screen is more complex than a button, but if we call it the cost of 10 buttons, a touch screen replaces more than 10 buttons...
For common functions separate buttons are better for UX. However the touch screen is cheaper.
I support Mazda's efforts here, but there are compelling commercial and engineering reasons to go in the other direction.
It blows my mind away how you can even begin to compare the predicted reliability of a complex touchscreen interface stuffed with active electronics to dumb buttons and wires with a straight face, let alone what fielded production units only a few years in have clearly demonstrated.
[1] https://www.thedrive.com/tech/27989/teslas-screen-saga-shows...
