The MCA implements a power key input in its firmware. You can use this input to connect a power button to the ConnectCore 8M Mini system to perform 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
The power button (ON/OFF) on the board is 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 SOMs Micro Controller Assist Power key (
CONFIG_INPUT_MCA_PWRKEY)
This option is enabled as built-in on the default ConnectCore 8M Mini kernel configuration file.
Kernel driver
The MCA power key driver is located at:
| File | Description |
|---|---|
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-powerkey.txt.
Power key inside the MCA
mca_cc8m: mca@63 {
...
pwrkey {
compatible = "digi,mca-cc8m-pwrkey";
digi,key-power;
digi,key-power-up;
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.
