Hacked Gadgets Forum

March 18, 2012

How to get 2 extra Pins from an Arduino

at 11:17 pm. Filed under DIY Hacks, Electronic Hacks


If you have an Arduino project and need a few extra pins have a look at the way that Mark from SpikenzieLabs did it. He removed the crystal and 22pf capacitors then he added a pin header to access the pins easily. To use this configuration you then need to set the fuses so that it uses the internal oscillator.  The internal oscillator is not as accurate as the internal RC time constant but most applications aren’t time critical so this is normally not an issue.



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3 Responses to “How to get 2 extra Pins from an Arduino”

  1. Philippe Says:

    If you have a design (not Arduino) that uses an Atmega168/328, you can also use the reset pin (pin 1). From the datasheet:

    “If the RSTDISBL Fuse is programmed, PC6 is used as an I/O pin. Note that the electrical char- acteristics of PC6 differ from those of the other pins of Port C.”

    The thing is that with this, you can only reset the uC by removing the power supply. This is not normally a problem on embedded designs that run in a continuous loop.

    On the Arduino the additional circuitry prevents using this trick: the line is pulled up through a 10k resistor, and down by the DTR and CTS signals.

  2. Patrick Says:

    If you want to do it correctly you have to edit the a arduino constant that defines the clockspeed. (Somewhere in a H file). If you use 8mhz and define is at the default 16 you delays etc arent correct.

  3. Remove your Arduino’s external oscillator to gain a free pair of IO pins - Hack a Day Says:

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