Power module

The power module manages power-related functionality for devices with nPM1300, like the Thingy:91 X, including the following:

• Monitoring battery voltage and calculating remaining battery percentage.
• Handling VBUS (USB) connect and disconnect events to enable or disable UART peripherals.
• Publishing battery percentage updates via zbus messages.

Messages

The Power module defines and communicates on the POWER_CHAN channel.

Input Messages

• POWER_BATTERY_PERCENTAGE_SAMPLE_REQUEST Requests a battery percentage sample.

Output Messages

• POWER_BATTERY_PERCENTAGE_SAMPLE_RESPONSE Contains the calculated battery percentage.

The power message structure is defined in power.h:

struct power_msg {
	enum power_msg_type type;

	/** Contains the current charge of the battery in percentage. */
	double percentage;
};

Configurations

The following Kconfig options control this module’s behavior:

• CONFIG_APP_POWER Enables the Power module.

• CONFIG_APP_POWER_DISABLE_UART_ON_VBUS_REMOVED If enabled, suspends UART devices when VBUS is removed.

• CONFIG_APP_POWER_THREAD_STACK_SIZE Size of the Power module’s thread stack.

• CONFIG_APP_POWER_WATCHDOG_TIMEOUT_SECONDS Defines the watchdog timeout for the module. Must be larger than the message processing timeout.

• CONFIG_APP_POWER_MSG_PROCESSING_TIMEOUT_SECONDS Maximum time spent processing a single message.

See the Kconfig.power file in the module’s directory for more details on the available Kconfig options.

Kconfig and device tree

• The Power module uses npm1300_charger as specified by device tree.
• The two UART devices uart0_dev and uart1_dev defined in device tree will be enabled or disabled based on VBUS events.

State diagram

The Power module uses a minimal state machine with a single state, STATE_RUNNING. In this state, the module:

1. Initializes the charger and optional fuel gauge in the state entry function.
2. Waits for messages to arrive via zbus.
3. Handles battery sample requests and publishes results.
4. Monitors for VBUS events to enable or disable UART devices.