Embedded controller: Difference between revisions

Revision as of 09:14, 1 March 2021

Revision as of 08:22, 31 October 2021

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An '''embedded controller''' ('''EC''') is a [[microcontroller]] in [[computer]]s that handles various system tasks that the [[operating system]] does not handle.

== Tasks ==

An embedded controller can have the following tasks:

*Receiving and processing signals from the keyboard<ref name="ps2kbc">http://www.computer-engineering.org/ps2keyboard/</ref> and the touchpad (including touchpad disable)

*Receiving and processing signals from the touchpad (including touchpad disable)

*other buttons and switches (e.g., power button, laptop lid switch (received from hall sensor))<ref name="amikey">http://www.ami.com/ami_downloads/Embedded_Controller_Data_Sheet.pdf</ref>

*Turning the computer on and off

*Controlling access to the [[A20 line]]<ref>http://www.win.tue.nl/~aeb/linux/kbd/A20.html</ref>

*Thermal measurement (CPU, GPU, Motherboard) and response including [[fan control]], [[Dynamic frequency scaling|CPU and GPU throttling]], and emergency shutdown in response to rising temperatures

*Controlling indicator [[Light-emitting diode|LED]]s (e.g. caps lock, scroll lock, num lock, battery, ac, power, wireless LAN, sleep)

*Managing the [[Battery (electricity)|battery]] charger and the battery<ref name="amikey"/>

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*[[Bluetooth]] toggle

*Display backlight toggle

*[[Local area network|LAN]] reset

*[[Graphics processing unit|GPU]] reset

*Can act as a bridge between [[BIOS]] chip and [[chipset]]

*Mute audio

*[[USB]] OC (overcurrent) (USB disable)

*whether [[Alternating current|AC]] is present

*Display power toggle

*Suspend Management (for sleep mode)

*Controls RGB lighting

*eSATA toggle

*Reset all [[PCI Express]] devices

*[[Wake-on-LAN]]

*3G or 4G toggle

*Debug Card Interface (Enables repair centers to monitor the boot process with a special device in an attempt to fix problems (only few several hundred codes))

*SCI from the Embedded Controller to inform the ACPI driver (in the {{abbr|OS|Operating system}}) of an ACPI Event

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An embedded controller is sometimes known as a "Keyboard Controller BIOS", which comes from the fact that the embedded controller evolved from the keyboard controller and often still is used as a keyboard controller. Even today, an ACPI embedded controller communicates with the CPU by using the same I/O ports that keyboard controllers used in the past.

A [[Trusted Platform Module]] (TPM) contains an embedded controller that performs [[Cryptography|cryptographic]] functions and nothing else.

== Ergonomics ==

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To prevent this, some embedded controllers are designed to run the fans at a constant speed over a larger range of temperatures and will only increase fan speed when the system is close to overheating. In this case, the ergonomics of the system are improved because the fan is quieter, as it is controlled to rotate at a lower speed and does not change speed as often. However, when the temperature does cross the controller's threshold, it will take much longer to reduce the temperature to safe levels.

To change the fan control policy, updates to the embedded controller's firmware are usually necessary. In some systems, fan control is not provided by the embedded controller, but is instead done by a higher-level component such as an ACPI controller. In this case, changing the behaviour of the fan system can be done by the system administrator through ACPI configuration without changing any firmware.

== See also ==

* [[Advanced Configuration and Power Interface]] (ACPI)

* [[Baseboard management controller]] (BMC)

* [[Super I/O]]

* [[Low Pin Count]] (LPC)

* [[System Management Bus]] (SMBus)

== References ==