Project title: Cable Tester RJ45 (Ethernet)

The concept for this project originated from a basic need in network installation tasks: checking non-standard or custom-built Ethernet (RJ45) cables. Standard LAN cable testers available on the market often cannot provide sufficient detailed information about the internal connection structure.

This tester was designed to solve that problem. It leverages the power of an Arduino Uno combined with a signal expansion chip to accurately check signal continuity and pin mapping.

Improving Performance with SN74HC595 Shift Register

The key component in the transmitter section of this project is the SN74HC595 IC, a Serial-in Parallel-out Shift Register. There are two main reasons for choosing this component in embedded systems engineering:

1. Resource Saving (I/O Expansion): The Arduino Uno has limited digital pins. Using the SN74HC595 allows us to use only 3 pins from the Arduino (Data, Latch, Clock) while controlling up to 8 output pins to send signals to all 8 LAN wires.
2. Precision Control: We can send data bitwise to freely apply 5V to the desired pins one by one in sequence.

Operating Principle and Program Logic (Engineering Logic)

The system operates using a Master-Slave Scanning approach. The operational steps are divided into the following cycle:

1. Transmitter Side: The program instructs the SN74HC595 to output a High voltage (5V) to each RJ45 pin sequentially, starting from pin 1 up to pin 8. This is done using the shiftOut() function to shift data bits. For example:

• Cycle 1: Send signal to pin 1 (00000001)
• Cycle 2: Send signal to pin 2 (00000010)
• ... Continue until all 8 wires are covered.

2. Receiver Side: While the transmitter is powering a specific pin, the receiver section (connected to the Arduino's input pins) scans to detect "which pin on the receiver side shows 5V".

3. Result Analysis:

• Straight-through Cable: If a signal is sent to pin 1 and voltage is detected at pin 1 on the receiver side (and this pattern holds for all 8 pins), the system will diagnose it as a perfectly functional standard cable.
• Crossed/Defective Cable: If a signal is sent to pin 1 but voltage appears at pin 6 on the receiver side, the system will immediately process and display on the screen that a pin swap has occurred. Or, if no voltage appears on any pin, it will immediately indicate that the wire is broken.

Conclusion

This project is not just a general cable testing tool, but also an excellent example of using a Shift Register to manage complex testing systems. It enables engineers or technicians to quickly analyze physical issues with signal cables via a display screen, effectively reducing the time spent on troubleshooting wiring on-site.