CrOS EC (Embedded Controller)

Configure LEDs

LEDs provide status about the following:

  • Dedicated battery state/charging state
  • Chromebook power
  • Adapter power
  • Left side USB-C port (battery state/charging state)
  • Right side USB-C port (battery state/charging state)
  • Recovery mode
  • Debug mode

LEDs can be configured as simple GPIOs, with on/off control only, or as PWM with adjustment brightness and color.

Config options

In config.h, search for options that start with CONFIG_LED* and evaluate whether each option is appropriate to add to baseboard.h or board.h.

  • CONFIG_LED_COMMON - Should be defined for both GPIO and PWM style LEDs.
  • CONFIG_LED_ONOFF_STATES - used for GPIO controlled LEDs
  • CONFIG_LED_PWM - used for PWM controlled LEDs. You must also define CONFIG_PWM when using PWM controlled LEDs.

Feature Parameters

  • CONFIG_LED_PWM_COUNT <count> - Must be defined when using PWM LEDs

Override the following parameters when using PWM LEDs if you don't want to use the recommended LED color settings. - CONFIG_LED_PWM_CHARGE_COLOR <ec_led_color> - CONFIG_LED_PWM_NEAR_FULL_COLOR <ec_led_color> - CONFIG_LED_PWM_CHARGE_ERROR_COLOR <ec_led_color> - CONFIG_LED_PWM_SOC_ON_COLOR <ec_led_color> - CONFIG_LED_PWM_SOC_SUSPEND_COLOR <ec_led_color> - CONFIG_LED_PWM_LOW_BATT_COLOR <ec_led_color>

GPIOs and Alternate Pins

For GPIO based LEDs, create GPIO() entries for all signals that connect to platform LEDs. The default state of the pins should be set so that the LED is off (typically high output).

For PWM LEDs, configure the ALTERNATE() macro, setting the module type to MODULE_PWM.

Data structures

For GPIO based LEDs: - struct led_descriptor led_bat_state_table[LED_NUM_STATES][LED_NUM_PHASES] - Must be defined when CONFIG_LED_ONOFF_STATES is used. Defines the LED states for the platform for various charging states.

For PWM based LEDs: - const enum ec_led_id supported_led_ids[] - Defines the LED type for all PWM LEDs in the system. See ./include/ec_commands.h for a description of the supported LED types. - struct pwm_led led_color_map[] - Defines the PWM intensity of the individual LEDs to generate the corresponding color. This table allows for custom tuning of the LED brightness and color. - const struct pwm_channels[] - Configures the PWM module, refer to the Configuring PWM section for details.

See the GPIO documentation for additional details on the GPIO macros.

Tasks

None required by this feature.

Testing and Debugging

Console Commands

  • pwmduty - TODO add description.
  • gpioset - For GPIO based LEDs, this command lets you directly change the state of the LED.
  • gpioget - For GPIO based LEDs, this reads current state of the pin. If the current state does not track changes made with gpioset, check your board for stuck at high or stuck at low condition.

If you're having problems with a PWM LED, try reconfiguring the pin as a GPIO to verify the board operation independent of the PWM module.

LED Driver Chips

LED driver chips are used to control the LCD panel backlight. The backlight control is separate from the platform LEDs.