Nov 232010

arduinoAuthor: John Smitty

Here is another option for getting your Arduino (or other PIC) connected to your network (ethernet) – use an old NSLU2!

The NSLU2 and Arduino both talk TTL, but the NSLU2 is 3.3v and Arduino is 5v. Simple fix – add a resistor!

Only 3 wires are required – pins 2, 3 and 4 on the NSLU2. You do not want to connect the power pin. Per the table below, look for the white stripe – that is the power pin.

NSLU2 – pin-out of the J2 serial port

Pin 1 – 3.3v, pin 1 has a white stripe next to it

Pin 2 – RXD, receive from Arduino to NSLU2 (must have resistor)

Pin 3 – TXD, transmit from NSLU2 to Arduino

Pin 4 – GND, ground connection

This article is written in reference to the “Freeduino” – a BBB (bare bones board) type. Make sure everything is powered off and unplugged. Then, connect the TTL pins labeled “RX”, “TX” and “GND” on the BBB to the proper pins on the NSLU2. The 4 serial port TTL pins on the NSLU2 are visible just below the battery to the right.

You must place a 10k resistor between the Arduino and the NSLU2 on pin 2 of the NSLU2 so the 5v coming from the Arduino are reduced to safe levels.

Now power up the Arduino and NSLU2 that is flashed with Debian (SlugOS should work also). Install minicom (apt-get) and start up minicom and set the serial port to ttyS0, 9600, 8N1.

If the connections are correct, the TTL pins/port on the Arduino and NSLU2 are functional you should now see the output from the Arduino. If you do not see anything, be sure you have pre-programmed your Arduino with a program that outputs text at the proper baud rate. Also try powering off both units, power back up and try again. If you have made other hardware mods such as overclocking on the NSLU2, it is possible the serial port will not work.


The 4 serial port pins are visible to the right just below the battery.

Yes, I simply soldered wires right in to the holes (after solder sucking the existing solder out) – even though other articles recommend using header pins / connectors.

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