[proteus simulation] Arduino UNO +74c922 keyboard decoding drive 4x4 matrix keyboard

【Proteus Simulation 】Arduino UNO +74C922 Keyboard decoding driver 4X4 Matrix keyboard

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• Proteus Simulation
  

This example uses 74C922 Decoding chip , Make the program code very simple , When pressing different keys , The nixie tube will display the corresponding key value . It's mainly about AVR Familiarity and understanding of operating instructions , stay Arduino It is operated in a bus mode IO Oral state , Than traditional Arduino The encapsulation instructions of will appear more concise and direct . face Arduino Programming , We should not limit ourselves to learning and mastering one kind of instruction operation mode .AVR Operating instructions are equivalent to taking off Arduino Packaging layer , So as to approach the register .

AVR Knowledge of operating instructions

• AVR Single chip microcomputer IO Port is a standard two-way port , First, set IO The state of the mouth , namely ： Input or output .

DDRx Register is AVR MCU port direction register , By setting DDRx You can set x The state of the port .
DDRx The corresponding bit of the port direction register is set to 1 Corresponding x The corresponding bit of the port is the output state ,DDRx The corresponding bit of the port direction register is set to 0 Corresponding x The corresponding bit of the port is the input state .

• for example ：

DDRA = 0xFF; // Set port A All ports are in output state ÿ