Robobot circuits
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Digital IO
Figure 1. The circuit diagram should ensure that each IO pin can function as both input and output. If input, then the pin has active pull down, i.e. for input to change, it must be pulled high, to at least 3.3V, but 5 or 12V will work too. If output, then a transistor is active when output is high, and can draw at least 1A from the 12V supply. The 5V and 3.3V can supply no more than 100mA.
Figure 2. The PCB layout for the digital IO circuit.