📏 Understanding Distance Concepts in PuffiMail

PuffiMail uses a time-of-flight distance sensor (VL53L0X) to detect whether new mail has arrived. It does this by comparing two key values: the Current Distance and the Baseline Distance.

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🔹 Current Distance

The real-time measured distance (in millimeters) from the sensor to the bottom of your mailbox.

• Automatically measured whenever the device is triggered (e.g., mailbox opens or sensor wakes up)
• A smaller value usually indicates that something (like mail) is present
• Displayed in the web interface or sent to MQTT as current

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🔹 Baseline Distance

A reference distance saved when the mailbox is completely empty.

• Acts as the "normal" distance with no mail inside
• Used to compare with current readings to determine mailbox status
• Can be updated manually from the web UI using the "Measure Distance" button
• Displayed as baseline in MQTT

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🔹 "Measure Distance" Button

Manually triggers a distance reading and sets it as the new baseline.

• Use this when:
• First installing the device
• Cleaning or re-emptying the mailbox
• Repositioning or adjusting the sensor
• PuffiMail will save the current reading as the new baseline

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✅ Status Example Table

Situation	Current Distance	Baseline Distance	Reported Status
Mailbox is empty	850 mm	850 mm	empty
New mail present	600 mm	850 mm	new_mail
Sensor error / invalid	-1 or NaN	850 mm	unknown

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💡 Tip: Always reset the Baseline Distance after installing or repositioning PuffiMail to ensure reliable detection.

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