Toggle-LEDs.ino

Toggle-LEDs

This example demonstrates the use of push buttons and LEDs and how to use shift registers and analog multiplexers to save pins.

Boards: 🛈

AVR, AVR USB, Nano Every, Nano 33 IoT, Nano 33 BLE, UNO R4, Pi Pico, Due, Teensy 3.x, ESP8266, ESP32

Connections

• SS: 74HC595 ST_CP
• MOSI: 74HC595 DS
• SCK: 74HC595 SH_CP
• 2: 74HC4067 A (COM OUT/IN)
• 3: 74HC4067 S0
• 4: 74HC4067 S1
• 5: 74HC4067 S2
• 6: 74HC4067 S3

Connect 16 momentary push buttons between the input pins of the multiplexer and ground.
The internal pull-up resistor for the buttons will be enabled automatically, so no external resistors are necessary.

Connect 16 LEDs (and series resistors) between the eight outputs of the two shift registers and ground.

Remember to connect the enable pins of both the multiplexer and the shift registers to ground in order to enable them. Also connect the master reset pin of the shift registers to Vcc.
Connect the serial data output of the first shift register (QH' or Q7S) to the serial input of the second shift register.

Behavior

Pressing the first button will turn on the first LED. Pressing it again will turn it off again. Pressing the second button will turn on the second LED. Pressing it again will turn it off again, and so on.

Written by PieterP, 2018-08-28
https://github.com/tttapa/Arduino-Helpers

 
#include <Arduino_Helpers.h> // Include the Arduino Helpers library.
 
#include <AH/Containers/ArrayHelpers.hpp>
#include <AH/Hardware/Button.hpp>
#include <AH/Hardware/ExtendedInputOutput/AnalogMultiplex.hpp>
#include <AH/Hardware/ExtendedInputOutput/SPIShiftRegisterOut.hpp>
 
// Instantiate a multiplexer
CD74HC4067 mux {
  2,            // input pin
  {3, 4, 5, 6}, // Address pins S0, S1, S2, S3
  // 7, // Optionally, specify the enable pin
};
 
// Alternatively, if you have a 3-bit mux:
// CD74HC4051 mux {
//   2,
//   {3, 4, 5},
//   // 7, // Optional
// };
 
// Instantiate a shift register with the SPI slave select pin as latch pin, most
// significant bit first, and a total of 16 outputs.
SPIShiftRegisterOut<mux.length()> sreg {SPI, SS, MSBFIRST};
 
// Instantiate an array of momentary push buttons.
// It generates an array of Buttons on pins:
// { mux.pin(0), mux.pin(1) ... mux.pin(15) }
// For each button it creates, it increments the pin number by 1,
// and it starts counting from mux.pin(0)
auto buttons =
  generateIncrementalArray<Button, mux.length()>(mux.pin(0), pin_int_t {1});
 
void setup() { // Initialize everything
  mux.begin();
  sreg.begin();
  for (Button &button : buttons)
    button.begin();
}
 
void loop() { // Check if a button is pressed, if so toggle the LED
  for (uint8_t i = 0; i < mux.length(); ++i)
    if (buttons[i].update() == Button::Falling)
      sreg.digitalWrite(i, sreg.digitalRead(i) ? LOW : HIGH);
}