I use the generic Motorola HD dock for my D4, and I was really disappointed at how dim the actual clock was in night mode. What I mean by that, is that the contrast between the actual numbers and the background is so small that I can sometimes not read the time at night without getting my face really close to the phone. How does the RAZR HD do in night mode? Pics would be helpful! Thanks
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Ok, continued to research this question and have some disappointing results for those who want to build your own smart charging cable or modify non-OEM dock to add autodetect functionality as on OEM ones.
Received motorola vehicle dock today. Measured the resistance between pinouts. Nothing special except well-known pin 5 and 4.
It have resistance of 200 kOhm.
Soldered another scheme with 200 kOhm resistor and connected other pins to logic data analyzer.
And i have this scenario:
When connecting 200k between pin 4 and 5, phone connects power to the standart microUSB pins for 2 seconds. During these 2 seconds it sends some data to D+ pin and expect some answer from connected accessory. Sure in my case it recieved nothing and after 2 sec. passed shuts the power on microUSB and operates like nothing connected. Scenario repeats if scheme reconnected.
Thus i think this is a good proof that resistance is used to detect accessory. But this is not enough and is just a first part of detection procedure.
Without special IC that is build in every moto accessory you'll never get autodetect feature.
Here is that IC in the attachment.
Anyone here have some reverse engineering skills to continue research?