Just another analog clock

While the Arduino examples list the 1.8" display in the "retired" area it still can be useful.

Just some lines of code, and the clock is ticking. If you have a real-time clock, you can use it instead of the millis() function.

/*
  clock
*/
#include <TFT.h>
#define cs   10
#define dc   9
#define rst  8
TFT tft = TFT(cs, dc, rst);
int T = 1000; // can be reduced
int w, h, mx, my, r;
const word c1 = 0xFF00;
const word c2 = 0x0FF0;
const word c3 = 0x00FF;

void setup() {
  Serial.begin(115200);
  Serial.println(__FILE__);
  tft.begin();
  tft.setRotation(0);
  w = tft.width();
  h = tft.height();
  mx = w / 2;
  my = h / 2;
  r = mx - 1;
  tft.background(0, 0, 0);
  tft.stroke(0, 255, 255);
  tft.rect(0, 0, w, h);
  tft.text("clock", 2, 2);
  byte r2;
  for (int i = 0; i < 60; i++) {
    if (i % 15 == 0)
      r2 = r - 15;
    else if (i % 5 == 0)
      r2 = r - 10;
    else
      r2 = r - 5;
    line(r2, r, i, ST7735_WHITE);
  }
}

float second, minute, hour;

void loop() {
  int t = millis() / T;
  // analog:
  // erase previous:
  line(0, r - 15, second, 0);
  line(0, r - 20, minute, 0);
  line(0, r - 25, hour * 5, 0);
  // calculate new angles:
  second = t % 60;
  minute = t / 60.0;
  while (minute > 60) minute = minute - 60;
  hour   = t / (60 * 60.0);
  while (hour > 12) hour = hour - 12;
  // draw new lines:
  line(0, r - 15, second, c1);
  line(0, r - 20, minute, c2);
  line(0, r - 25, hour * 5, c3);
  // digital:
  Serial.print(hour, 0);
  Serial.print(":");
  Serial.print(minute, 0);
  Serial.print(":");
  Serial.println(second);
  // erase previous:
  tft.fillRect(78, 2, 47, 10, 0);
  tft.setCursor(78, 2);
  print2(hour);
  tft.print(":");
  print2(minute);
  tft.print(":");
  print2(second);
  delay(T);
}

void print2(byte b) {
  if (b < 10) tft.print(0);
  tft.print(b);
}

void line(byte r1, byte r2, float n, word c) {
  float phi = n / 60.0 * TWO_PI - HALF_PI;
  byte x1 = mx + r1 * cos(phi);
  byte y1 = my + r1 * sin(phi);
  byte x2 = mx + r2 * cos(phi);
  byte y2 = my + r2 * sin(phi);
  tft.stroke(c);
  tft.line(x1, y1, x2, y2);
}
 
 
hj

Want a real time clock?

If you just add a real-time clock module equipped with the DS1307 you can use this code:

/*
  clock
*/
#include <TFT.h>
#define cs   10
#define dc   9
#define rst  8
TFT tft = TFT(cs, dc, rst);
int T = 1000; // can be reduced
int w, h, mx, my, r;
const word c1 = 0xFF00;
const word c2 = 0x0FF0;
const word c3 = 0x00FF;

#include <RTClib.h>
RTC_DS1307 RTC;
DateTime now;

void setup() {
  Serial.begin(115200);
  Serial.println(__FILE__);
  Serial.println(__DATE__ " " __TIME__);
  tft.begin();
  tft.setRotation(3);
  w = tft.width();
  h = tft.height();
  mx = w / 2;
  my = h / 2;
  r = my - 1;
  tft.background(0, 0, 0);
  tft.stroke(0, 255, 255);
  tft.rect(0, 0, w, h);
  tft.text("clock", 2, 2);
  byte r2;
  for (int i = 0; i < 60; i++) {
    if (i % 15 == 0)
      r2 = r - 15;
    else if (i % 5 == 0)
      r2 = r - 10;
    else
      r2 = r - 5;
    line(r2, r, i, ST7735_WHITE);
  }
  initRTC();
}

byte second, minute, hour;

void loop() {
  int t = millis() / T;
  // analog:
  // erase previous:
  line(0, r - 15, second, 0);
  line(0, r - 20, minute, 0);
  line(0, r - 25, hour * 5, 0);
  now = RTC.now();
  second = now.second();
  minute = now.minute();
  hour = now.hour();
  // draw new lines:
  line(0, r - 15, second, c1);
  line(0, r - 20, minute, c2);
  line(0, r - 25, hour * 5, c3);
  // digital:
  Serial.print(hour);
  Serial.print(":");
  Serial.print(minute);
  Serial.print(":");
  Serial.println(second);
  // erase previous:
  tft.fillRect(111, 2, 47, 10, 0);
  tft.setCursor(111, 2);
  print2(hour);
  tft.print(":");
  print2(minute);
  tft.print(":");
  print2(second);
  delay(T);
}

void print2(byte b) {
  if (b < 10) tft.print(0);
  tft.print(b);
}

void line(byte r1, byte r2, float n, word c) {
  float phi = n / 60.0 * TWO_PI - HALF_PI;
  byte x1 = mx + r1 * cos(phi);
  byte y1 = my + r1 * sin(phi);
  byte x2 = mx + r2 * cos(phi);
  byte y2 = my + r2 * sin(phi);
  tft.stroke(c);
  tft.line(x1, y1, x2, y2);
}

void initRTC() {
  RTC.begin();
  Serial.println("shorten pins 2+3 to force"
                 " adjust after upload");
  pinMode(2, OUTPUT);
  pinMode(3, INPUT_PULLUP);
  boolean forceAdjust = !digitalRead(3);
  tft.setCursor(2, h-20);
  tft.print("RTC is");
  tft.setCursor(2, h-10);
  if (! RTC.isrunning() || forceAdjust) {
    Serial.println("NOT running!");
    tft.print("RTC adjusted to __TIME__");
    // following line sets the RTC to the
    // date & time this sketch was compiled
    RTC.adjust(DateTime(__DATE__, __TIME__));
  }
  else tft.print("running");

}

Some Arduino clones have Serial and I2C pins next to the SPI header. The I2C pins match exactly the I2C pins of the RTC module.