OpenParcelBox/hardware/reverse-engineering/reverse-engineering.md

Boks One Reverse Engineering

Objective

This document centralizes information collected during analysis of the original Boks One hardware.

No assumption should be considered validated until it has been experimentally verified.

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General Information

Item	Value	Status
Model	Boks One	Confirmed
Revision	TBD	Pending

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Power Supply

Battery

Information	Value	Status
Technology	8x AAA cells	Confirmed
Nominal voltage	12 V, 8x 1.5 V	Confirmed
Capacity	Depends on selected cells	Confirmed

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Keypad

Configuration

• Vertical 2x6 physical format.

Pinout

Pin	Function	Status
TBD	TBD	To identify

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Lock Mechanism

Model

Information	Value	Status
Manufacturer	KERONG	Confirmed
Model	KR-S79	Confirmed
Variant	KR-S79_20-JST	Confirmed
Revision	2023.10_KERONG	Confirmed
Manufacturing date	17-10-2023	Confirmed
Patent	ZL.201821837049.2	Confirmed

Characteristics

Parameter	Value	Status
Supply voltage	8 to 24 V DC	Confirmed
Maximum current	100 mA	Confirmed
Auxiliary contact	COM / NO / NC, 3 A max	Confirmed
Connector	JST	Confirmed
Harness length	20 cm	Confirmed

Manufacturer Pinout

Color	Function
Red	+V
Orange	GND
Yellow	SIG
Black	COM
Green	NO
White	NC

Boks Harness Mapping

Boks Side	Lock Side	Function
Blue	Red	+V
White	Orange	GND
Green	Yellow	SIG
Yellow	Black	COM
Black	Green	NO
Red	White	NC

Validated Behavior

Command

Action	Result
Supply between +V and GND	Lock remains closed
Pulse SIG to +V	Opens
Pulse SIG to GND	No effect

Feedback Contact

Lock State	COM to NO	COM to NC
Locked	Closed	Open
Unlocked	Open	Closed

Behavior

The COM/NC contact changes state as soon as the latch leaves the locked position.

This feedback confirms unlocking immediately without waiting for the full mechanism travel.

Current development wiring:

• NC is connected to XIAO D7.
• COM is connected to XIAO D8.
• The firmware drives D8 low and reads D7 with an internal pull-up.
• When COM/NC closes, D7 reads low.

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Sensor

State feedback is integrated directly into the KERONG KR-S79 lock through a COM / NO / NC changeover contact.

No external sensor has been identified.

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Connectors

Connector	Pin Count	Function	Status
JST	6	KR-S79_20-JST lock	Confirmed
Keypad	TBD	Matrix keypad	To identify

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Electrical Measurements

Measurement	Value	Date	Comment
Lock supply voltage	13.36 V	2026-07	New 8x AAA battery pack
SIG at rest	13.36 V	2026-07	Measured against GND
SIG to +V	Opens	2026-07	Experimentally validated
SIG to GND	No effect	2026-07	Experimentally validated

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Photos

Electronic Board

To be completed.

Keypad

To be completed.

KR-S79_20-JST Lock

To be completed.

JST Connector

To be completed.

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Use in OpenParcelBox

The lock is controlled by the Seeed Studio XIAO BLE nRF52840.

The current development firmware generates a 150 ms positive SIG pulse and monitors COM/NC independently for open-state feedback. The remaining target for command-result validation is:

1. Generate a positive pulse on SIG.
2. Start a timeout.
3. Monitor the COM/NC contact.
4. If COM/NC changes before the timeout, confirm opening.
5. Otherwise, report an opening failure.

This strategy confirms a real unlock event instead of assuming opening after a fixed delay.

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Notes

• The Boks-installed variant is KR-S79_20-JST.
• The NO / NC markings match the experimentally observed behavior documented here.
• The lock includes its own control electronics; only a positive pulse on SIG is required to trigger opening.
• All information above was experimentally validated on an original Boks replacement lock.