LED and key on an Arduino Uno

// LED and key: a TM1638 "LED&KEY" board with the TM1638plus library. Each
// button lights the LED above it while held, and the display counts the
// presses and names the last button.
//
//   TM1638  STB -> 4, CLK -> 6, DIO -> 7, VCC -> 5 V, GND -> GND
//
// The TM1638 holds the picture itself and scans the buttons itself, so the
// sketch only sends bytes: STB low, then each byte least significant bit
// first, clocked on CLK's rising edge. readButtons() sends 0x42 and the chip
// answers with four bytes on DIO, one bit per button once they are folded
// together.
//
// Things to try. Press two buttons at once. Then change the brightness in
// setup() from 2 to 7, and to 0.

#include <TM1638plus.h>

const int STROBE_PIN = 4;
const int CLOCK_PIN = 6;
const int DATA_PIN = 7;

TM1638plus tm(STROBE_PIN, CLOCK_PIN, DATA_PIN);

uint8_t lastButtons = 0;
unsigned long presses = 0;

void show(int button) {
  // "P" and the count on the left, a gap, the button's number on the right.
  char text[9] = "P       ";
  unsigned long n = presses % 100000UL;
  int at = 5;
  do {
    text[at--] = (char)('0' + n % 10);
    n /= 10;
  } while (n > 0 && at > 0);
  text[7] = (char)('0' + button);
  tm.displayText(text);
}

void setup() {
  Serial.begin(9600);
  tm.displayBegin();
  tm.brightness(2);
  tm.displayText("LED KEY ");
  Serial.println("TM1638 ready");
}

void loop() {
  uint8_t buttons = tm.readButtons();
  if (buttons != lastButtons) {
    tm.setLEDs((uint16_t)buttons << 8);
    uint8_t pressed = buttons & ~lastButtons;
    for (int i = 0; i < 8; i++) {
      if (pressed & (1 << i)) {
        presses++;
        show(i + 1);
        Serial.print("S");
        Serial.print(i + 1);
        Serial.print(" pressed, ");
        Serial.print(presses);
        Serial.println(" in all");
      }
    }
    lastButtons = buttons;
  }
  delay(20);
}