The Fonera has 3.3V TX/RX logic, I have a launchpad and an Arduino, can I use any of the cable/boards to reprogram or access the serial on a fonera?

Fonera serial info is here: http://www.dd-wrt.com/wiki/index.php/LaFonera_Hardware_Serial-Cable-Port#Accessing_serial_console_on_the_Fon

I am specifically asking about methods and boards not covered in this previous Q: Can I use an Arduino as a USB to serial interface?


Yes, the answer is the top post in Can I use an Arduino as a USB to serial interface?

Use the FTDI chip by wiring your Fonera to the TX and RX pins on the Arduino and run a sketch on the Arduino which doesn't use those pins.

  • \$\begingroup\$ -1 because while the question and answer are very old, it is still wrong. A 5v serial connection to a 3.3v device would almost always require a level shifter. Connecting it directly can damage the 3.3v device. \$\endgroup\$ – Passerby Nov 3 '13 at 14:35

The Arduino boards are typically 5v devices, and have either an FTDI FT232 usb-to-serial IC, or a ATMega16u2 usb microcontroller with usb-to-serial code.

To connect the serial pins 0 and 1 to a separate device, you either need to remove the Arduino's main microcontroller, or make sure it does not try to access the serial pins (a blank sketch would do).

To connect them to a 3.3v device, you would need a level shifter. The Fonera will not tolerate 5v on its serial pins.

The MSP430 Valueline Launchpad runs at 3.6v, as does the IC providing the serial connection. 3.6v is close enough to the 3.3v Fonera levels that it should be okay. Most ICs can accept VCC + 0.3v on any given input pin. No guarantees though.

As a note, the Fonera requires 9600 baud. The Launchpad UART is limited to 9600 baud, hardcoded, so it will work with the Fonera, but not with some newer devices that need a faster serial speed.


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