In ARDUINO we have 20 I/O pins, so we can program 20 pins of UNO to be used as either input or output. Although there are more pins on ATMEGA328P controller than on UNO, this is because while designing the board some pins are defaulted. Now for some applications we need more than 30 pins, say if we want to design a 5x5x5 LED CUBE, so for this we need 5x5+5=30pins. For such cases we use serial to parallel co ...

The Siemens DLO7135 Dot matrix LED is one amazing piece of optoelectronics. It's billed as a 5x7 Dot Matrix Intelligent Display (r) with Memory/Decoder/Driver. Along with that memory, it's got a 96-character ASCII display set with upper and lower case characters, a built-in character generator and multiplexer, four levels of light intensity, and it all runs on 5V. That's a lot to live up to, and at $16 a po ...