3.3V Digital Input/Output

June 2, 2017


evive has two bi-directional logic level shifters which are accessible from digital pin 36 and 37 in Arduino IDE and the flow of direction is controlled by digital pin 33. evive use 74LVC245 for level shifting.

evive 3.3V Input Output


Programming in Arduino IDE

  1. By changing the state of digital pin 33, you can change the characteristics of the logic shifter as an input or output.
    1. If the state of digital pin 33 is HIGH, then the IO3V3 pins act as OUTPUT pins,
    2. If the state is LOW, then they act like INPUT pins. 
      evive Notes Icon
      Note: The digital pin 33 should always be configured as the output.
  2. Digital pins 36 and 37 are directly connected to the level shifter. Level shifter takes 5V input and output from the digital pins and converts them to 3.3V I/O. This 3.3V I/O pins are shown in the figure.
    1. If you want to give 3.3V output from these pins then you have to configure digital pins 36 and 37 as OUTPUT pins in Arduino IDE.
    2. You can use IO3V3 pins as input anytime without configuring them as INPUT or OUTPUT. 
      evive Alert
      Alert: But you have to change the state of digital pin 33 to LOW before reading.


This code demonstrates the use of bidirectional logic shifter as 3.3V digital output and input. Connect the positive pin of the LED to IO3V3 pin 1 and negative pin to the GND.
The code will link the LED using 3.3V digital output as well as read the state of LED and IO3V3 pin 2.

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