Table of Contents
Serial Debug Setup
Serial debugging is the most commonly used hardware debugging method in router unbricking. Through TTL Serial, you can view boot logs and access the Bootloader command line.
Hardware Preparation
| Tool | Description |
|---|---|
| USB-to-TTL Module | CH340/PL2303/FT232, 3.3V |
| Dupont wires | 4 or more, male-to-female |
| Multimeter | Measure voltage, identify pins |
| Screwdriver set | For disassembling router |
Serial Connection
Pin Identification
There are typically 4 serial pins on the router motherboard:
| Pin | Function | Description |
| ββ | ββ | ββ |
| TX | Transmit | Connect to RX of TTL module |
| RX | Receive | Connect to TX of TTL module |
| GND | Ground | Connect to GND of TTL module |
| VCC | Power | Do NOT connect, used only to identify voltage |
Connection Steps
1. Locate the serial pins on the router motherboard (usually 4 adjacent header pins) 2. Use a multimeter to confirm GND (connected to large copper area or shielding) 3. Identify TX and RX (try connecting first, swap if baud rate is wrong) 4. Do NOT connect VCC! 5. Connect USB-to-TTL module to computer
Software Setup
Serial Tools
| Tool | Platform | Description |
| ββ | ββ | ββ |
| PuTTY | Windows | Most commonly used |
| SecureCRT | Windows | Full-featured |
| screen | Linux/macOS | Command line tool |
| CoolTerm | Cross-platform | Simple and easy |
Serial Parameters
| Parameter | Value |
| ββ | ββ |
| Baud rate | 115200 (most common), 57600, 9600 |
| Data bits | 8 |
| Stop bits | 1 |
| Parity | None |
| Flow control | None |
PuTTY Setup
1. Select Connection type: Serial 2. Serial line: COM3 (check in Device Manager) 3. Speed: 115200 4. Click Open
screen Setup (Linux/macOS)
```bash # List serial devices ls /dev/ttyUSB*
# Connect (115200 baud) screen /dev/ttyUSB0 115200
# Exit screen Ctrl+A then K, then Y ```
Common Issues
No Output
* Check if baud rate is correct (115200/57600/9600) * Try swapping TX and RX * Check if GND is connected correctly * Confirm flow control is set to None in the serial tool
Garbled Output
* Baud rate mismatch, try other baud rates * Check data bits/stop bits/parity settings
Display but Not Responding
* May need to press Enter to activate * Some devices require a specific key to enter command line
Safety Notes
* Do NOT connect the VCC pin - may fry the router * Use a 3.3V TTL module * Disconnect power before hot-swapping