Stand-alone Arduino

  
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A Video Switcher which can be controlled using the computer`s parallel port. Unfortunately, fewer PCs are fitted with parallel pors these days and, for a laptop, it`s not really an option so the need to control the Switcher through a USB port became important. The Video Switcher only needs three digital inputs so, although the PICAXE range of Microcontrollers would probably
Stand-alone Arduino - schematic

provide a chip with a more economical use of pins, the Arduino seems easier to interface with a standard USB cable and it`s a useful enough project to justify building a cut down stand-alone Arduino. A stand-alone Arduino can conveniently be divided into two parts: The ATMega328 with its associated support components and the USB-to-Serial interface needed to upload sketches and provide the serial communication that was to replace the parallel port. I`d decided from the outset to use an ATmega328 with the Arduino bootloader already programmed in and not to complicate things by using a `blank` chip. I bought the pre-programmed ATmega328 and the other components from HobbyTronics as they`re based relatively locally to me (in the UK at least!). The 328 has a convenient pinout label already attached! The USB to Serial converter supplies 5 volts to the Arduino from the computer`s USB socket. There are several different USB to Serial converters available, all of which do more or less the same job. I found the Sparkfun Breakout Board for FT232RL (shown to the right) a bit fiddly to handle and it was necessary to desolder the 3. 3 volt solder bridge and bridge the 5 volt pads instead. It`s shown on the schematic but is a bit hard to spot unless you`re aware of it. It`s also necessary to solder the two 9-way male header strips to the board. I used a BV104 breakout board made by ByVac (shown above) which is described as a "Silicon...



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