Here is a simple 7 Segment clock which displays the time, the date and device temperature.
It uses a
DS3231 AT24C32 Memory Module For Arduino IIC Precision RTC
TM1637 4 digits display (with centre colon : )
Grounding pin 7 displays date & month
Grounding Pin 6 shows temperature
Step 1: Connecting the Hardware
For the Display
CLK = 9; //Set the CLK pin connection to the display
DIO = 8; //Set the DIO pin connection to the display
For the RTC
SDA Arduino pin A4
SCL Arduino pin A5
SQW Arduino pin 3 - Alarm interrupt
For display update interrupt
Arduino pin 13 to Arduino pin 2
Step 2: The Software
The sketch is attached and is pretty self explanatory.
In my previous rtc instructable, I set the SQW output to 1Hz and used the output to interrupt the Arduino to update the display.
The bit INTCON (reg 0Eh ) is set to 0 for a a constant 1Hz Square wave out.
I wanted to set an alarm which means this bit must be set to 1. It only triggers when the alarm condition is true, so I needed another way to update the display every second.
I could have used millis() in the loop, but I chose to use the Arduino internal timer interrupt (new ground for me !).
This link is brilliant, its what I used to set the interrupt.
Every second, pin 13 changes state, this fires interrupt 0 (pin 2) on the Arduino which updates the display.
I used Alarm 2 and set it to generate an interrupt every minute :-
See the datasheet (link below) to set the alarm for a specific time / date.
(The ISR just sets a flag & prints a message on the Arduino screen and does nothing practical though it could be used to trigger a relay or LED or buzzer etc. !)
//set alarm 2 every minute
I had to convert the bits to decimal as the rtc is programmed using BCD.
The set_td(x,y) function converts the data and writes it to the rtc registers.
This function is also called to set the date & time registers.
To write to the display, I had the help of this link
The colon ':' flashes every second by setting the high bit of the second display digit (see code).
Displaying the temperature comes from here :-
NOTE : if the temperature is 19 degrees, the Arduino Serial.println has a problem and displays it as -238, my guess is because 9 in BCD sets the MSB which for the temperature register which is stored as a two's compliment sets the 'sign' bit - just a guess ! HOWEVER, it is displayed on the 7 Segment correctly.