Power handling for Windows 8 and Windows 8.1 touch and pen controllers
This topic provides information about touch controller power states for Windows 8 and Windows 8.1, and guidelines for touch controller IHVs, PC ODMs, and PC OEMs. It assumes that the reader is familiar with the touch hardware requirements in the Windows® Hardware Certification Kit (Windows HCK), and PC and device power states in general.
Background
In today’s mobile computer systems, extending battery life is a top priority. Minimizing device power consumption in idle scenarios and eliminating it entirely in standby scenarios are fundamental to realizing system power goals.
Touch and pen controllers are only required to be input ready when the screen is on. However, the screen state – whether the screen is on or off – isn’t communicated directly to the controller.
A touch/Pen controller connects to the system over USB or I2C. If the system supports connected standby, we highly recommend that you use I2C. When the system is in connected standby, touch and pen digitizers must consume less than or equal to 1 mW.
We strongly recommend that all of the guidance in this section is followed for both HID I2C and USB pen controllers.
In this section
| Topic | Description |
|---|---|
This topic describes the three required (and an optional fourth) power states for HID I2C peripherals. |
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This topic describes the three power states that are required for internal and external HID USB devices. |
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This topic introduces power rail switching design. |
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This topic introduces SET_POWER (ON/SLEEP), an in-band power management mechanism that is provided for by the HID I2C protocol. |
Related topics
Windows pointer device data delivery protocol
How to design multi-touch hardware solutions for Windows 8 and Windows 8.1