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# MCA power key input

The MCA implements a power key input in its firmware. You can use this input to connect a power button to the ConnectCore 6UL system for performing the following power events:

- Send the system to suspend
- Wake the system up from suspend
- Send the system to power down
- Power up the system

Both the ConnectCore 6UL SBC Express and SBC Pro contain a power button (ON/OFF) connected to the MCA power key input.

## Kernel configuration

You can manage the MCA power key driver support through the following kernel configuration option:

- Digi ConnectCore 6UL Micro Controller Assist Power key (CONFIG_INPUT_MCA_CC6UL_PWRKEY)

This option is enabled as built-in on the default ConnectCore 6UL kernel configuration file.

## Platform driver mapping

The MCA power key driver is located at:

File | Description
--- | ---
drivers/input/misc/pwrkey-mca-cc6ul.c | MCA power key driver

## Device tree bindings and customization

The MCA power key input device tree binding is documented at Documentation/devicetree/bindings/input/digi,mca-cc6ul-powerkey.txt.

### Power key inside the MCA

    Common ConnectCore 6UL device tree

        mca_cc6ul: mca@7e {

            ...

            pwrkey {
                compatible = "digi,mca-cc6ul-pwrkey";
                digi,key-power;
                digi,key-sleep;
                digi,debounce-ms = <100>;
                digi,pwroff-delay-sec = <6>;
                digi,pwroff-guard-sec = <30>;
            };
        };

## Using the power key

### Suspend to memory

The Linux kernel can perform a suspend-to-memory or suspend-to-RAM operation. When entering this low-power mode, the system state is kept in self-refreshing RAM while the system enters a low-power-consumption mode. The system resumes when a previously selected interrupt is received, restores the previous state, and continues running from where it left off.

- To suspend, press the power key for less than the time specified in device tree property digi,pwroff-delay-sec (six seconds by default.)
- To resume, briefly press the power key.

### Power off

The Linux kernel can perform a power-off operation that places the Power Management IC (PMIC) in power off mode, disabling all power sources that are not needed for wake up.

- To perform a controlled software power-off sequence, press the power key for longer than the time specified in device tree property digi,pwroff-delay-sec (six seconds by default.)
- To power on, briefly press the power key.

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MCA power key input updated on 22 January 2018 02:43:37 PM