Linksys WRT150N v1 Serial mod



  • Locate a serial port on the main board
  • Convert the serial port signals from 3.3 Vcc to 5 Vcc to enable communication with a standard PC
  • Create a small test circuit with the parts required to convert the signals from 3.3Vcc to 5 Vcc

Locate serial port on main board

The WRT150N has a serial port located on the front of the circuit next to the security button. When the router is open and seen from top front the pins are located as follows (left to right)

  1. Ground
  2. Not used
  3. Rx
  4. Tx
  5. Vcc 3.3v

The connecter mounted to the main board are shown below. The other wires on the board should be ignored they are from a previous SD mod.

IMG_7872 - Copy
Serial port pins added to WRT150N v1 circuit.

Converting the serial port on the main board to a PC compatible serial port

To use the serial port with an ordinary PC the voltage has to be raised to 5 Vcc which the RS232 operate on. This can be done by using a MAXIM 3232CPE IC which has support of converting two serial ports from 3.3 Vcc to 5 Vcc.


Description from

3,0 till 5,5 V RS232-sändare/mottagare Fabr Maxim Transceiver för +3,3 och +5 V-system. Behöver endast 4 st 0,1 μF kondensatorer. Pinkompatibel med MAX 232

Creating a small test circuit with the MAXIM 3232 IC

Here a small print has been fitted with the required components, the MAXIM 3232 IC and the corresponding compensators. The IC is powered by the Gound and 3.3Vcc from the connector described above.

The serial port DB9 and connector from the main board is attached as shown:

  • PIN 11: T1IN to main board Tx
  • PIN 12: R1OUT to main board Rx
  • PIN 14: T1OUT to Rx on serial port connector
  • PIN 13: R1IN to Tx serial port connector

The rest of the PIN connection can be seen in the data sheet for the MAX3232CPE.

IMG_8350 IMG_8349

IMG_8348 IMG_8347 

You can now use the serial port with your PC. If you don't have a serial port on your laptop etc you can use a serial port to USB cable.

The serial port is used by the kernel to send debug information under startup and continues send log messages. The port setting is 115200 8N1.


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