Arduino clock with DS3231 and ST7735 color display
Arduino clock with DS3231 and ST7735 color display
In the last Arduino project I built a simple real time clock using DS1307 RTC and ST7735 TFT display (link is below) and in this project I’m going to show how to build a real time clock with RTC chip temperature monitor using Arduino, DS3231 RTC and the same display (ST7735 TFT).
The ST7735 TFT is a color display which has a resolution of 128×160 pixel and it communicates with the master device using SPI (Serial Peripheral Interface) protocol.
The DS3231 is more accurate than the DS1307 due to its built-in temperature sensor. It also (the DS3231) keeps time running even if the main power source is down (with the help of 3V battery). It also uses I2C interface to communicate with the master device which is in this case the Arduino.
To see how to interface Arduino with ST7735 TFT display, visit the following post:
Arduino ST7735 1.8″ TFT display example
To see how to interface Arduino with DS1307 RTC and ST7735 color TFT display, take a look at this post:
Arduino Real time clock with ST7735 color TFT and DS1307
Hardware Required:
- Arduino board
- ST7735S (ST7735R) TFT screen
- DS3231 module —-> DS3231 datasheet
- 5 x 1k ohm resistor
- 2 x push button
- 3V coin cell battery
- Breadboard
- Jumper wires
Arduino clock with ST7735 display and DS3231 RTC circuit:
The image below shows project circuit schematic diagram.
The ST7735S shown in project circuit diagram has 8 pins: (from right to left): RST (reset), CE (chip enable), DC (or D/C: data/command), DIN (data in), CLK (clock), VCC (5V or 3.3V), BL (back light) and Gnd (ground).
Normally the ST7735 display works with 3.3V only, but many boards of this display have a built-in 3.3V regulator (AMS1117 3V3) like the one shown in the circuit diagram. This regulator supplies the display controller with 3.3V from 5V source.
All Arduino UNO board output pins are 5V, connecting a 5V pin directly to the ST7735 display board may damage its controller circuit. To avoid that, I connected each control line of the display to the Arduino board through 1k ohm resistor.
So, the ST7735 display is connected to the Arduino board as follows (each one through 1k resistor):
RST pin is connected to Arduino digital pin 8,
CS pin is connected to Arduino digital pin 9,
D/C pin is connected to Arduino digital pin 10,
DIN pin is connected to Arduino digital pin 11,
CLK pin is connected to Arduino digital pin 13.
The DS3231 RTC module SDA (serial data) and SCL (serial clock) pins are respectively connected to Arduino A4 and A5 pins (ATmega328P hardware I2C module pins).
The two push buttons which are connected to Arduino digital pins 6 and 7 are for setting time & date of the clock.
Arduino clock with ST7735 display and DS3231 RTC code:
The following Arduino code requires 3 libraries from Adafruit Industries:
Adafruit ST7735 display library
Adafruit graphics library —-> direct link
Adafruit RTC library —-> direct link
After the download, go to Arduino IDE —> Sketch —> Include Library —> Add .ZIP Library … and browse for the .zip file (previously downloaded).
The same thing for the other library files.
So, in the code there are total of 4 libraries, they’re included as follows:
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#include <Wire.h> // include Arduino Wire library (required for I2C devices)
#include <Adafruit_GFX.h> // include Adafruit graphics library
#include <Adafruit_ST7735.h> // include Adafruit ST7735 TFT library
#include <RTClib.h> // include Adafruit RTC library
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The ST7735 TFT display is connected to Arduino hardware SPI module pins (clock and data), the other pins which are: RST (reset), CS (chip select) and DC (data/command) are defined as shown below:
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#define TFT_RST 8 // TFT RST pin is connected to arduino pin 8
#define TFT_CS 9 // TFT CS pin is connected to arduino pin 9
#define TFT_DC 10 // TFT DC pin is connected to arduino pin 10
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And the two push buttons are defined in the code as:
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// button definitions
#define button1 7 // button B1 is connected to Arduino pin 9
#define button2 6 // button B2 is connected to Arduino pin 8
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Functions used in the code:
bool debounce (): this function is for button B1 debounce, returns 1 if button is debounced.
void RTC_display(): displays day of the week, date and time on the display.
byte edit(byte parameter): this function is for setting the real time clock, returns the edited parameter.
Rest of code is described through comments.
Full Arduino code:
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/*
* Arduino real time clock using DS3231 and ST7735 color TFT (128×160 pixel)
* This is a free software with NO WARRANTY.
* http://simple-circuit.com/
*/
#include <Wire.h> // include Arduino Wire library (required for I2C devices)
#include <Adafruit_GFX.h> // include Adafruit graphics library
#include <Adafruit_ST7735.h> // include Adafruit ST7735 TFT library
#include <RTClib.h> // include Adafruit RTC library
#define TFT_RST 8 // TFT RST pin is connected to arduino pin 8
#define TFT_CS 9 // TFT CS pin is connected to arduino pin 9
#define TFT_DC 10 // TFT DC pin is connected to arduino pin 10
// initialize ST7735 TFT library
Adafruit_ST7735 tft = Adafruit_ST7735(TFT_CS, TFT_DC, TFT_RST);
// initialize RTC library
RTC_DS3231 rtc;
DateTime now;
// buttons definition
#define button1 7 // button B1 is connected to Arduino pin 7
#define button2 6 // button B2 is connected to Arduino pin 6
void setup(void)
{
pinMode(button1, INPUT_PULLUP);
pinMode(button2, INPUT_PULLUP);
rtc.begin(); // initialize RTC chip
tft.initR(INITR_BLACKTAB); // initialize a ST7735S chip, black tab
tft.fillScreen(ST7735_BLACK); // fill screen with black color
tft.drawFastHLine(0, 20, tft.width(), ST7735_BLUE); // draw horizontal blue line at position (0, 44)
tft.drawFastHLine(0, 75, tft.width(), ST7735_BLUE); // draw horizontal blue line at position (0, 44)
tft.drawFastHLine(0, 130, tft.width(), ST7735_BLUE); // draw horizontal blue line at position (0, 102)
tft.setTextColor(ST7735_WHITE, ST7735_BLACK); // set text color to white and black background
tft.setTextSize(1); // text size = 1
tft.setCursor(4, 0); // move cursor to position (4, 10) pixel
tft.print(“ARDUINO + ST7735 TFT”);
tft.setCursor(28, 10); // move cursor to position (28, 27) pixel
tft.print(“+ DS3231 RTC”);
tft.setCursor(14, 134); // move cursor to position (28, 27) pixel
tft.print(“CHIP TEMPERATURE:”);
tft.setTextSize(2); // text size = 2
tft.setTextColor(ST7735_MAGENTA, ST7735_BLACK); // set text color to magneta and black background
tft.setCursor(37, 84); // move cursor to position (37, 112) pixel
tft.print(“TIME:”);
}
// a small function for button1 (B1) debounce
bool debounce ()
{
byte count = 0;
for(byte i = 0; i < 5; i++)
{
if ( !digitalRead(button1) )
count++;
delay(10);
}
if(count > 2) return 1;
else return 0;
}
void RTC_display()
{
char _buffer[11];
char dow_matrix[7][10] = {“SUNDAY”, “MONDAY”, “TUESDAY”, “WEDNESDAY”, “THURSDAY”, “FRIDAY”, “SATURDAY”};
byte x_pos[7] = {29, 29, 23, 11, 17, 29, 17};
static byte previous_dow = 8;
// print day of the week
if( previous_dow != now.dayOfTheWeek() )
{
previous_dow = now.dayOfTheWeek();
tft.fillRect(11, 55, 108, 14, ST7735_BLACK); // draw rectangle (erase day from the display)
tft.setCursor(x_pos[previous_dow], 29);
tft.setTextColor(ST7735_CYAN, ST7735_BLACK); // set text color to cyan and black background
tft.print( dow_matrix[now.dayOfTheWeek()] );
}
// print date
sprintf( _buffer, “%02u-%02u-%04u”, now.day(), now.month(), now.year() );
tft.setCursor(4, 52);
tft.setTextColor(ST7735_YELLOW, ST7735_BLACK); // set text color to yellow and black background
tft.print(_buffer);
// print time
sprintf( _buffer, “%02u:%02u:%02u”, now.hour(), now.minute(), now.second() );
tft.setCursor(16, 107);
tft.setTextColor(ST7735_GREEN, ST7735_BLACK); // set text color to green and black background
tft.print(_buffer);
}
byte edit(byte parameter)
{
static byte i = 0, y_pos,
x_pos[5] = {4, 40, 100, 16, 52};
char text[3];
sprintf(text,“%02u”, parameter);
if(i < 3) {
tft.setTextColor(ST7735_YELLOW, ST7735_BLACK); // set text color to green and black background
y_pos = 52;
}
else {
tft.setTextColor(ST7735_GREEN, ST7735_BLACK); // set text color to yellow and black background
y_pos = 107;
}
while( debounce() ); // call debounce function (wait for B1 to be released)
while(true) {
while( !digitalRead(button2) ) { // while B2 is pressed
parameter++;
if(i == 0 && parameter > 31) // if day > 31 ==> day = 1
parameter = 1;
if(i == 1 && parameter > 12) // If month > 12 ==> month = 1
parameter = 1;
if(i == 2 && parameter > 99) // If year > 99 ==> year = 0
parameter = 0;
if(i == 3 && parameter > 23) // if hours > 23 ==> hours = 0
parameter = 0;
if(i == 4 && parameter > 59) // if minutes > 59 ==> minutes = 0
parameter = 0;
sprintf(text,“%02u”, parameter);
tft.setCursor(x_pos[i], y_pos);
tft.print(text);
delay(200); // wait 200ms
}
tft.fillRect(x_pos[i], y_pos, 22, 14, ST7735_BLACK);
unsigned long previous_m = millis();
while( (millis() – previous_m < 250) && digitalRead(button1) && digitalRead(button2)) ;
tft.setCursor(x_pos[i], y_pos);
tft.print(text);
previous_m = millis();
while( (millis() – previous_m < 250) && digitalRead(button1) && digitalRead(button2)) ;
if(!digitalRead(button1))
{ // if button B1 is pressed
i = (i + 1) % 5; // increment ‘i’ for the next parameter
return parameter; // return parameter value and exit
}
}
}
void loop()
{
if( !digitalRead(button1) ) // if B1 is pressed
if( debounce() ) // call debounce function (make sure B1 is pressed)
{
while( debounce() ); // call debounce function (wait for B1 to be released)
byte day = edit( now.day() ); // edit date
byte month = edit( now.month() ); // edit month
byte year = edit( now.year() – 2000 ); // edit year
byte hour = edit( now.hour() ); // edit hours
byte minute = edit( now.minute() ); // edit minutes
// write time & date data to the RTC chip
rtc.adjust(DateTime(2000 + year, month, day, hour, minute, 0));
while(debounce()); // call debounce function (wait for button B1 to be released)
}
now = rtc.now(); // read current time and date from the RTC chip
RTC_display(); // diaplay time & calendar
// read chip temperature
Wire.beginTransmission(0x68); // start I2C protocol with DS3231 address
Wire.write(0x11); // send register address (temperature MSB)
Wire.endTransmission(false); // I2C restart
Wire.requestFrom(0x68, 2); // request 2 bytes from DS3231 and release I2C bus at end of reading
byte t_msb = Wire.read(); // read temperature MSB
byte t_lsb = Wire.read(); // read temperature LSB
// print chip temperature
char _buffer[6];
uint16_t chip_temp = (uint16_t)t_msb << 2 | t_lsb >> 6;
if(t_msb & 0x80) {
chip_temp |= 0xFC00;
sprintf(_buffer, “-%02u.%02u”, abs((int)chip_temp * 25) / 100, abs((int)chip_temp * 25) % 100);
}
else
sprintf(_buffer, ” %02u.%02u”, (chip_temp * 25) / 100, (chip_temp * 25) % 100);
tft.setCursor(11, 146);
tft.setTextColor(ST7735_RED, ST7735_BLACK); // set text color to red and black background
tft.print(_buffer);
tft.drawCircle(90, 148, 2, ST7735_RED); // print degree symbol ( ° )
tft.setCursor(95, 146);
tft.print(“C”);
delay(100); // wait 100ms
}
// end of code.
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The following video shows my protoboard circuit:
