Serial Logging on the Wii U

You may review the logs leading up to a system hang or crash by viewing the system log in the System Log Viewer menu in the System Config Tool. The system has a circular log buffer of approximately 64KB that may still be available. However, there is a hardware issue that causes the log to be erased if you do not restart the system quickly.

You may also obtain the log output via the serial logging interface on a devkit (CAT-DEV or CAT-R) that is in headless mode. With the serial logging interface, logs are output as they are printed from the application by using functions such as OSReport. When the USB-to-Serial adapter is connected the first time after a hang occurs, the system sends out any logs stored in the buffer.

This document discusses the serial logging process and provides information about the physical adapters and cables that are needed to perform serial logging on the Wii U.

For information about saving the system log (or syslog), see Saving System Logs to an SD Card.


To connect the CAT-DEV to the host PC for serial logging, a USB-to-Serial adapter and a crossover cable are required. If the host PC does not have a serial port, an additional USB-to-Serial adapter is needed for the host PC.

USB-to-Serial Adapter

The Wii U does not have a serial port. There is also a high probability that the host PC does not have a serial port. Because of the simplicity of the RS232 standard, the Wii U uses a serial interface to dump logs. Not just any USB-to-Serial adapter works for this process.

Serial Adapter Chipsets

USB-to-Serial adapters are not simple cable rearrangements. They require a chip to convert from the serial interface (RS232) to the USB interface. There are two common chipsets in use to do this conversion. The first is the PL2303 family of chips made by Prolific. The second common chipset is the FT232 family of chips made by FTDI. These two companies do not make USB-to-Serial adapters; they simply make the chips that are packaged into many different retail adapters. When purchasing an adapter, it is important to confirm which chipset that the adapter is based on.

Serial Adapter for the Wii U

The Wii U requires a USB-to-Serial adapter that uses the FTDI FT232B or FT232R chipset. Since the Wii U has drivers only for these chipsets and no other drivers may be installed, this is a hard requirement. For details on purchasing an FTDI serial adapter, contact the supplier of your choice.

The Gearmo PRO Single Port USB-to-Serial Adapter with Activity LED is recommended for a CAT-DEV. For purchasing details, contact the supplier of your choice.

The adapters shown in the table below have been tested and verified to work with CAT-DEV and CAT-R.

Table 1: USB-to-Serial Adapters
Make Model Chip Set
VSCOM USB to RS-232 Cable FTDI FT232B
QVS USB to RS-232 Cable FTDI FT232B

There is no plan for supporting other adapters.

If you are emulating a final production runtime environment, do not connect a USB-to-Serial adapter to the CAT-R. When the adapter is connected to the console display output, there is a small amount of system overhead added when the system loads, such as CPU utilization and MEM2 traffic.
If OSReport output exceeds the rate that the debugging interface can handle, messages may be dropped. This rare behavior is by design to ensure that system performance is not adversely affected by blocking until the printing could catch up. When this happens, the following message is printed:
******* log buffer overrun, some text was dropped *******

Serial Adapter for the Host PC

Because any driver may be installed on a PC, virtually any available USB-to-Serial adapter with any chipset should work on the host PC. USB-to-Serial adapters may be found for as little as a few dollars. However, some of the inexpensive USB-to-Serial adapters claim have the Prolific PL2303 chipset when they actually substitute a chipset that is distributed by another manufacturer. To work properly, these devices require an older version of the Prolific driver ( Even with the older driver, they may not provide the desired performance. For example, some characters may be garbled. The older version of the driver is not plug-and-play via Windows Update and may be harder to find. When ordering a less expensive USB-to-Serial device with the Prolific chipset, ensure a driver disc is included. After installing the driver, you may update the device driver version to in the Windows Device Manager.

Cross-Over Cable

If you are using a USB-to-Serial adapter on the devkit and the host PC, you need a cross-over cable, also called a null modem, to connect the two adapters. Cross-over cables swap the send and receive pins on one end of the serial connection, enabling the data that is sent from the devkit to be received by the host PC. It is important that you do not simply purchase a serial extension cable, which does not swap these pins. A cross-over cable may be purchased inexpensively from many online retailers.


Terminal emulation software is required on the host PC that is configured as follows:

Table 2: Terminal Software Configuration
Speed 57600 bps
Data 8-bit
Parity none
Stop 1-bit
Flow Control none
Terminal New-line CR+LF

A small, stand-alone program is provided that automatically configures the terminal emulation software as specified, logs all output, and saves the output to a file on request. You may find the program in the $CAFE_ROOT/system/tool/CatLog directory.

Troubleshooting Serial Logging

Receive limited or no log output

When limited or no log output is received from a devkit, the most likely cause is a connection problem. Confirm that all connectors are properly connected and working. After checking the connections, verify that the System Mode is set to Development Mode. The System Mode may be configured in the Boot Configuration menu of the System Config Tool.

Revision History

2014/01/09 Slight content adjust.
2013/12/18 Removed group references.
2013/09/23 Merged in other serial logging information.
2011/02/21 Initial version.