feat(oled): Implement brightness control and auto-power save for bread-compact-wifi

[parkghost]

Description

This PR implements comprehensive power management and brightness control for OLED displays, specifically targeting the bread-compact-wifi board.

Key Features:

1. Hardware Power Control: Implemented SetPowerSaveMode in OledDisplay to use esp_lcd_panel_disp_on_off for true hardware sleep/wake.
2. Brightness/Contrast Control:
   • Added SetContrast using command 0x81.
   • Implemented OledBacklight adapter to map brightness (0-100) to contrast (0-255).
   • Smart Threshold: Setting brightness <= 5% turns off the display power completely; > 5% turns it on and sets contrast.
3. Auto Power Save:
   • Integrated PowerSaveTimer in CompactWifiBoard.
   • Automatically turns off the screen after 60 seconds of inactivity.
   • Wakes up on Button (Boot, Touch, Volume) events or Voice activity.
4. MCP Integration: Exposed OledBacklight via GetBacklight, enabling the standard self.screen.set_brightness tool for voice control (e.g., "Turn off screen", "Set brightness to 50").

Testing

• Validated on bread-compact-wifi-128x64.
• Verified voice commands for brightness and screen on/off.
• Verified auto-sleep timeout.

Related Issue

• 可以给设备加上长时间待命状态下自动息屏的功能吗 #796

[78]

This feature should be optional.

Auto-off screens should not be mandatory for all OLED board types.

[parkghost]

I understand this is an optional feature. Is there an easy way to configure whether it is enabled or disabled, or does this currently require maintaining a custom Xiaozhi branch?

[78]

Check this file: https://github.com/78/xiaozhi-esp32/blob/main/main/Kconfig.projbuild

You can open the menuconfig in the root directory of the project with the following command:

# idf.py menuconfig

[78]

Hi. Why not just override SetBrightnessImpl in OledBacklight to call SetContrast?

[parkghost]

Thanks for the suggestion. The reason I overrode SetBrightness instead of only SetBrightnessImpl is related to the transition timer in the base class.

The base Backlight::SetBrightness starts a periodic timer that steps brightness by 1 every 5ms, calling SetBrightnessImpl on each tick. This works great for PWM-based LCD backlights where the hardware produces a visually smooth fade. However, for OLED displays, each step sends an I2C 0x81 contrast command — the result doesn't look like a smooth transition but rather feels like input lag (up to 500ms).

I overrode SetBrightness to bypass the transition and apply the contrast instantly, but I realize this duplicates base class logic and requires making SetBrightness virtual.

Do you have any suggestions? I'd be happy to make corrections.