Fix charging detection when usb-c cable is plugged in

[marcoag]

Summary

Adds automatic USB charging detection that enters charging mode when cable is connected during operation.

Changes

• src/main.c:
  • Added DETECT_CHARGING event flag and periodic task (500ms interval)
  • Implemented charging status monitoring that detects USB cable connection
  • Automatically enters charging mode (BOOT) when charging status transitions from not charging to charging
  • Added forward declaration for disp_charging() function

Behavior

• USB plugged in while device is running: Automatically enters charging mode within 500ms
• After exiting charging mode: Stays in NORMAL/DOWNLOAD modes while USB remains connected
• USB unplugged and re-plugged: Automatically re-enters charging mode

Technical Implementation

The DETECT_CHARGING task runs every 500ms and tracks charging state transitions using a static was_charging flag. When it detects a transition from not charging to charging (is_charging && !was_charging), it:

1. Sets mode to BOOT (charging mode)
2. Calls disp_charging() to show charging animation
3. Calls mode_setup_normal() to restore normal operation after charging display completes

Test Plan

• Plug in USB while in NORMAL mode → enters charging mode
• Plug in USB while in DOWNLOAD mode → enters charging mode
• Press power button in charging mode → exits to NORMAL mode
• USB remains connected after exit → stays in NORMAL/DOWNLOAD modes
• Unplug and re-plug USB → re-enters charging mode

Dependencies

Might require #117.

Summary by Sourcery

Introduce periodic USB charging detection to automatically enter charging mode when power is connected during operation.

Bug Fixes:

• Ensure the device correctly transitions into charging mode when USB power is connected while the device is already running.

Enhancements:

• Add a periodic charging detection task that monitors USB power state and triggers charging mode on transition from not-charging to charging.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adds a periodic charging detection task that monitors USB power state and automatically transitions the device into charging (BOOT) mode when a cable is connected during operation, then returns to normal mode after displaying the charging screen.

Sequence diagram for DETECT_CHARGING task and charging mode transition

sequenceDiagram
    participant TMOS as TMOS_scheduler
    participant Common as common_tasks
    participant Power as charging_status
    participant Display as disp_charging
    participant Mode as mode_setup_normal

    TMOS->>Common: DETECT_CHARGING event (every 500ms)
    Common->>Power: charging_status()
    Power-->>Common: is_charging
    alt transition from not charging to charging
        Common->>Common: mode = BOOT
        Common->>Display: disp_charging()
        Display-->>Common: charging_animation_complete
        Common->>Mode: mode_setup_normal()
    else no transition to charging
        Common->>Common: update was_charging
    end
    Common-->>TMOS: clear DETECT_CHARGING flag

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Flow diagram for DETECT_CHARGING periodic task logic

flowchart TD
    A[DETECT_CHARGING event triggered every 500ms] --> B[Read charging_status and assign is_charging]
    B --> C{is_charging == 1 and was_charging == 0}
    C -- Yes --> D[Set mode to BOOT]
    D --> E[Call disp_charging to show charging animation]
    E --> F[Call mode_setup_normal to restore normal operation]
    C -- No --> G[Skip charging transition]
    F --> H[Set was_charging = is_charging]
    G --> H[Set was_charging = is_charging]
    H --> I[Clear DETECT_CHARGING event flag and return]

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File-Level Changes

Change	Details	Files
Introduce a periodic charging detection event that drives automatic transitions into charging mode when USB power is newly detected.	Added a DETECT_CHARGING event flag to the common event bitmask Hooked DETECT_CHARGING handling into common_tasks with edge detection logic using a static was_charging flag and charging_status() On transition from not charging to charging, set mode to BOOT, invoke disp_charging(), then call mode_setup_normal() to restore normal operation Configured a reload task in spawn_tasks to fire DETECT_CHARGING every 500ms Added a forward declaration for disp_charging() so it can be called from common_tasks	src/main.c

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[sourcery-ai]

Hey - I've left some high level feedback:

• Consider extracting the 500000 / 625 interval for DETECT_CHARGING into a named constant (similar to ANI_FLASH_SPEED_T etc.) so the charging detection cadence is self-documenting and easier to tweak.
• If disp_charging() can block for a noticeable duration, calling it directly from common_tasks may delay handling of other events; you might want to move the charging animation to its own task or make disp_charging() non-blocking.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Consider extracting the `500000 / 625` interval for `DETECT_CHARGING` into a named constant (similar to `ANI_FLASH_SPEED_T` etc.) so the charging detection cadence is self-documenting and easier to tweak.
- If `disp_charging()` can block for a noticeable duration, calling it directly from `common_tasks` may delay handling of other events; you might want to move the charging animation to its own task or make `disp_charging()` non-blocking.

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[bessman]

When transitioning from normal mode to the charge screen, pixels which were lit in normal mode are not turned off unless they are touched by the charging animation.

[bessman]

This fixes the leftover lit pixels:

Suggested change

	disp_charging();
	fb_fill(fb, 0);
	disp_charging();

[jerji]

When unplugging, the battery icon gets drawn on top of the text and it looks jank.