Suspend to RAM¶

This state offers significant power savings as everything in the system is put into a low-power state, except for memory, which is placed into the self-refresh mode to retain its contents.

NOTE: The test in this section was performed with LCD display disconnected.

To suspend to RAM:

Enable Wi-Fi if not enabled to ensure the firmware is loaded:

ifconfig wlan0 up

Disable Wi-Fi to put it into sleep state:

ifconfig wlan0 down

Disable Bluetooth:

echo 0 > /sys/class/gpio/gpio132/value

Enter Sleep mode:

pm-suspend

Wake up¶

There are many possible ways to wake up from suspend. A few examples: - Pushing the ON/OFF button (when present on the board) - Pushing a button on the board which has the boolean property "gpio-key,wakeup" set in its device tree node (under gpio_keys), e.g.:

    gpio-keys {
        compatible = "gpio-keys";
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_gpio_keys>;

        back {
            label = "Back";
            gpios = <&gpio5 20 GPIO_ACTIVE_LOW>;
            linux,code = <KEY_BACK>;
            gpio-key,wakeup;
        };
    };

Current consumption when suspended¶

To measure the current remove resistor R4 on the 6ULCustomBoard and connect an ammeter instead. The expected measured current consumption should be around 4.5mA at 3.3V