My Light Diagram

It’s entirely logical that low-cost miniature microcontrollers have fewer ‘legs’ than their bigger brothers and sisters – sometimes too few. The author has given some consideration to how to economise on pins, making them do the work of several. It occurred that one could exploit the high impedance feature of a tri-state output. In this way the signal produced by the high impedance state could be used for example as a CS signal of two ICs or else as a RD/ WR signal.  Circuit diagram: Multitasking Pins Circuit Diagram All we need are two op-amps or comparators sharing a single operating voltage of 5 V and outputs capable of reaching full Low and High levels in 5-V operation (preferably types with rail-to-rail outputs). Suitable examples to use are the LM393 or LM311.The resistances in the voltage dividers in this circuit are uniformly 10 kilo ohms. Consequently input A lies at half the operating voltage (2.5 V), assuming nothing is connected to the input – or the microcontroller pi...

It’s entirely logical that low-cost miniature microcontrollers have fewer ‘legs’ than their bigger brothers and sisters – some-times too few. The author has given some consideration to how to economise on pins, making them do the work of several. It occurred that one could exploit the high-impedance feature of a tri-state output. In this way the signal produced by the high-impedance state could be used for example as a CS signal of two ICs or else as a RD/WR signal. Multitasking Pins  Schematic All we need are two op-amps or comparators sharing a single operating voltage of 5 V and outputs capable of reaching full Low and High levels in 5-V operation (preferably types with rail-to-rail outputs). Suitable examples to use are the LM393 or LM311.The resistances in the voltage dividers in this circuit are uniformly 10 kilohms. Consequently input A lies at half the operating voltage (2.5 V), assuming nothing is connected to the input or the microcontroller pin connected is at high impe...