JCI (the company that Mazda hired to design the CMU) has created a flawed design. If your CMU is broken, there is no repair that a user can do. Do NOT contact me asking how to fix your CMU.

The touchscreen display is by Visteon (now parent company of JCI):

The HDCP link between the CMU and the display is achieved via technology from Maxim called "GMSL". What is useful about GMSL is that it achieves a display link plus I2C for touchscreen interfacing over a single differential pair of wires. What is frustrating about it is that it is proprietary and not available for purchase from distributors.

The engineering wisdom of using GMSL seems questionable. The length of the cable from the CMU to the display is mere inches. Any weight or cost savings through fewer wires is more than offset by the weight and cost of the extra circuitry. It is not congruent with the SkyActive philosophy.

I have to suspect that the touchscreen display is a standard module intended to be sold to across multiple vehicles and manufacturers. Its features would play more towards, say, a rear seat display module. For this usage, GMSL was just the opportunity cost of the module's usage.

The multi-touch controller is an Atmel MX1224. A 10-touch controller is more functionality than Mazda Connect utilizes, which again leads credence to the notion that this is a standard module.

A further indictment of this is that the power connector of the display is immediately adapted (via another short wiring harness) to a more proprietary power connector. This is also not congruent with the SkyActive philosophy of weight savings.

The USB hub is a standard module clearly intended to be used across many/all Mazda vehicles.

It is utilizing a SMSC (now Microchip) USB82642, which provides a hub plus SD card reader.

The rest of the circuitry is to provide a beefy +5V supply from automotive +12V and to provide a clean AUX audio input connection.

Here is the Commander Dial:

It is Freescale S9 (apparent descendant of the venerable 68HCxx series) plus a Atmel LIN transceiver with an integrated LDO.

I know that LIN is *supposed* to save money, but there doesn't seem to be cost-savings relative to CAN products in the present marketplace.

The Commander Dial also demonstrates a design philosophy Mazda uses throughout its present vehicles. All night-time lighting is achieved via dedicating copper wiring to each and every device to power the (LED) lighting at the user-set brightness.

For SkyActive, though, where every gram of weight counts, I would have thought they might have done differently. Perhaps they could have leveraged CAN and LIN to propagate the brightness level throughout the vehicle, and have each local microcontroller control FETs to drive the LEDs. That should save weight and cost. However, if JCI is writing your software, I can't blame Mazda for not wanting the risk that software bugs could cause flickering or the wrong brightness whilst driving at night.


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