ldo

[中文]

Overview

The ldo peripheral type describes an on-chip general-purpose LDO channel. BMGR generates an esp_ldo_channel_config_t from this configuration and calls the ESP-IDF esp_ldo_regulator.h to acquire the LDO channel. This type is used for board-level resources that need to be powered by the SoC on-chip LDO, such as MIPI DSI or CSI related power supplies.

After configuring ldo in board_peripherals.yaml, supported devices can reference the peripheral by name in their device-side peripherals list. BMGR obtains the LDO handle via the peripheral reference when initializing the device and releases the reference when the device is destroyed.

Supported Operating Modes

ldo does not use role or format to split modes. The configuration axis is a single LDO channel.

Minimal Configuration

LDO Channel

board_peripherals.yaml:

peripherals:
  - name: ldo_mipi
    type: ldo
    config:
      chan_id: 3
      voltage_mv: 2500
      adjustable: 1
      owned_by_hw: 0

Mode Description

ldo creates one on-chip LDO channel. chan_id, voltage_mv, adjustable, and owned_by_hw are generated directly into esp_ldo_channel_config_t for the ESP-IDF LDO driver to acquire the channel.

When using this peripheral, the LDO channel and output voltage must come from the target SoC datasheet and board schematic. The device side only references the LDO peripheral name; LDO channel, voltage, and ownership configuration must not be written into device-side reference entries.

Full Field Reference

LDO Channel — Full Fields

- name: ldo_mipi
  type: ldo
  config:
    # LDO (Low-Dropout Regulator) configuration for power management
    # This is an hardware-specific configuration, please refer your SoC's datasheet for valid LDO channel IDs
    # You must specify a LDO channel ID manually, based on your board schematic.
    # e.g. For ESP32_P4, the valid values for chan_id are 1-4,
    # where channel 1 and channel 2 are respectively used for powering the internal Flash and PSRAM,
    # channels 3 and 4 can be used to power external devices
    # In P4 Function-EV Board, channel 3 is used for powering the MIPI phy
    chan_id: 3                     # [TO_BE_CONFIRMED] LDO channel ID

    # Output voltage in millivolts (default: 2500 for 2.5V)
    # Common values: equal to 3300 or between 500 to 2700, depending on device requirements
    voltage_mv: 2500                # [TO_BE_CONFIRMED] Output voltage in millivolts

    # Whether voltage is adjustable (default: 1 for true)
    # Valid values: 0 (fixed), 1 (adjustable)
    adjustable: 1

    # Hardware ownership flag (default: 0 for software control)
    # Valid values: 0 (software-controlled), 1 (hardware-controlled)
    owned_by_hw: 0

Field sources:

  • YAML template: esp_board_manager/peripherals/periph_ldo/periph_ldo.yml.

  • Header file: esp_board_manager/peripherals/periph_ldo/periph_ldo.h.

Applicable Devices

device type

Usage

Notes

display_lcd

The dsi sub-type references ldo_mipi in the device-side peripherals

DSI display devices manage MIPI power supply references via the LDO peripheral

camera

The csi sub-type references ldo_mipi in the device-side peripherals

CSI camera devices can use dont_init_ldo together with the LDO peripheral to avoid duplicate LDO initialization inside the device

Reference Code

  • esp_board_manager/devices/dev_display_lcd/dev_display_lcd_sub_dsi.c

  • esp_board_manager/devices/dev_camera/dev_camera_sub_csi.c

Board-Level Reference

  • esp_board_manager/boards/esp32_p4_function_ev/board_peripherals.yaml: ldo_mipi configuration.

  • esp_board_manager/boards/esp32_p4_function_ev/board_devices.yaml: display_lcd and camera reference ldo_mipi.

  • esp_board_manager/boards/m5stack_tab5/board_peripherals.yaml: ldo_mipi configuration.

  • esp_board_manager/boards/m5stack_tab5/board_devices.yaml: display_lcd and camera reference ldo_mipi.

Notes

  • chan_id and voltage_mv are board-level hardware parameters that must be filled in according to the SoC datasheet and schematic.

  • chan_id and voltage_mv must be non-negative integers.

  • adjustable and owned_by_hw only accept 0 or 1.

  • When the same LDO is referenced by multiple devices, each device-side entry uses the same peripheral name; BMGR manages the handle with reference counting.

  • After modifying the LDO peripheral configuration, re-run idf.py bmgr -b <board>.

Debugging Tips

API Reference

Use esp_board_manager_get_periph_handle() to retrieve the LDO peripheral handle. The handle type is the ESP-IDF native esp_ldo_channel_handle_t, which can be passed to the esp_ldo_channel_* APIs for voltage adjustment.

Related declarations are in esp_board_manager/peripherals/periph_ldo/periph_ldo.h.

Underlying ESP-IDF driver documentation: Low-Dropout Regulator (LDO).

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