Custom OpenWrt-based Repeater Firmware for HLK-7628N
Budget: $1,000 – $2,000 USD
Statement of Work (SOW)
Project Title: Custom OpenWrt-based Repeater Firmware for HLK-7628N
Client: PIGEON POST
Developer: [Freelancer/Developer Name]
Date: March 24, 2025
1. Project Overview
This project involves building a custom firmware image for HLK-7628N modules (https://www.hlktech.net/index.php?id=435), based on OpenWrt, to be used in an ad-hoc mesh-like WiFi network. The goal is to create a dynamic chain of repeater units that autonomously configure their connectivity during field deployment.
All communication will take place over 2.4GHz WiFi only, per the limitations of the MT7628 chipset. All units except the gateway will operate without IPV6, or firewall services.
All WiFi passwords are protected using WPA2
2. Network Architecture and Workflow
Gateway Unit (First Unit):
Manually powered on by operator.
Broadcasts two SSIDs: common and pigeon_01
Repeater Units:
Operator carries all units powered off.
After placing a unit, the operator immediately powers on the next unit and continues walking with it.
Each repeater, once powered on, will:
Scan all SSIDs matching the pattern pigeon_XX.
Within the first 10 seconds, connect as a STA to the strongest AP in terms of RSSI.
After connection:
Broadcast two SSIDs as AP:
common
pigeon_XY where XY = (connected unit's XX) + 1
This continues to form a chain of repeaters. Clients should connect only to the common SSID.
3. Failover Logic
If a repeater loses its connection to the AP it was originally associated with:
It retries reconnecting for 5 seconds.
If failed, it will try to connect to the next strongest pigeon_XX network with a lower XX than its current.
This prevents loops.
Even after reconnecting to a new AP, it continues to scan for the original AP.
If the original AP's RSSI is stronger than the replacement AP for more than 30 seconds, it switches back.
4. LED Behavior
Only the “wifi” LED physically located on the HLK-7628N module itself will be used:
Normal Mode:
Slow blinking while scanning.
Solid ON when connected to AP.
Fast blinking when RSSI of AP drops below defined threshold.
Back to solid ON if RSSI stabilizes for 5+ seconds.
Chain End Indication:
This part does not occur when the repeater is simply powered on, but only in a situation where another repeater was previously connected to it as a STA to the backbone network.
If no repeater is connected anymore via pigeon_XX (i.e., no STA client), The LED flashes 3 short blinks, then pauses for 1500 milliseconds, and repeats the cycle continuously.
Resumes solid ON once a new STA connects to the backbone AP.
6. Deliverables
Custom OpenWrt firmware image for HLK-7628N.
Auto-start behavior as described.
LED indicators per above logic.
Documentation of how to flash the firmware.
Remote support to guide integrators through flashing.
7. Configuration and Customization
All thresholds (RSSI levels, scanning intervals, reconnect timers) must be stored in plain text config files accessible via SSH.
This allows the integrator team to adjust them during field testing without developer assistance.
8. Scope Limitations
The gateway unit and password generator unit will be pre-configured by the integrators.
The developer is not responsible for their setup.
Project Title: Custom OpenWrt-based Repeater Firmware for HLK-7628N
Client: PIGEON POST
Developer: [Freelancer/Developer Name]
Date: March 24, 2025
1. Project Overview
This project involves building a custom firmware image for HLK-7628N modules (https://www.hlktech.net/index.php?id=435), based on OpenWrt, to be used in an ad-hoc mesh-like WiFi network. The goal is to create a dynamic chain of repeater units that autonomously configure their connectivity during field deployment.
All communication will take place over 2.4GHz WiFi only, per the limitations of the MT7628 chipset. All units except the gateway will operate without IPV6, or firewall services.
All WiFi passwords are protected using WPA2
2. Network Architecture and Workflow
Gateway Unit (First Unit):
Manually powered on by operator.
Broadcasts two SSIDs: common and pigeon_01
Repeater Units:
Operator carries all units powered off.
After placing a unit, the operator immediately powers on the next unit and continues walking with it.
Each repeater, once powered on, will:
Scan all SSIDs matching the pattern pigeon_XX.
Within the first 10 seconds, connect as a STA to the strongest AP in terms of RSSI.
After connection:
Broadcast two SSIDs as AP:
common
pigeon_XY where XY = (connected unit's XX) + 1
This continues to form a chain of repeaters. Clients should connect only to the common SSID.
3. Failover Logic
If a repeater loses its connection to the AP it was originally associated with:
It retries reconnecting for 5 seconds.
If failed, it will try to connect to the next strongest pigeon_XX network with a lower XX than its current.
This prevents loops.
Even after reconnecting to a new AP, it continues to scan for the original AP.
If the original AP's RSSI is stronger than the replacement AP for more than 30 seconds, it switches back.
4. LED Behavior
Only the “wifi” LED physically located on the HLK-7628N module itself will be used:
Normal Mode:
Slow blinking while scanning.
Solid ON when connected to AP.
Fast blinking when RSSI of AP drops below defined threshold.
Back to solid ON if RSSI stabilizes for 5+ seconds.
Chain End Indication:
This part does not occur when the repeater is simply powered on, but only in a situation where another repeater was previously connected to it as a STA to the backbone network.
If no repeater is connected anymore via pigeon_XX (i.e., no STA client), The LED flashes 3 short blinks, then pauses for 1500 milliseconds, and repeats the cycle continuously.
Resumes solid ON once a new STA connects to the backbone AP.
6. Deliverables
Custom OpenWrt firmware image for HLK-7628N.
Auto-start behavior as described.
LED indicators per above logic.
Documentation of how to flash the firmware.
Remote support to guide integrators through flashing.
7. Configuration and Customization
All thresholds (RSSI levels, scanning intervals, reconnect timers) must be stored in plain text config files accessible via SSH.
This allows the integrator team to adjust them during field testing without developer assistance.
8. Scope Limitations
The gateway unit and password generator unit will be pre-configured by the integrators.
The developer is not responsible for their setup.