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The Raspberry Pi doesn’t have an RTC chip on it but with an expansion board you can add this
A popular chip is the DS3231 , lets have a quick look at this chip
DS3231 Information
I used a Pioneer600 board which has one of these chips on it among other features
Parts
The Pioneer600 costs around $39 for many useful features
Name | Link |
Raspberry Pi 4 | Aliexpress product link |
Raspberry Pi Expansion Board Pioneer600 | Aliexpress product link |
DS3231 Examples
C example using the BCM library
[codesyntax lang=”cpp”]
#include <bcm2835.h> #include <stdio.h> #include <unistd.h> //regaddr,seconds,minutes,hours,weekdays,days,months,yeas char buf[]={0x00,0x00,0x22,0x06,0x27,0x12,0x19}; char *str[] ={"SUN","Mon","Tues","Wed","Thur","Fri","Sat"}; void pcf8563SetTime() { bcm2835_i2c_write(buf,8); } void pcf8563ReadTime() { buf[0] = 0x00; bcm2835_i2c_write_read_rs(buf ,1, buf,7); } int main(int argc, char **argv) { if (!bcm2835_init())return 1; bcm2835_i2c_begin(); bcm2835_i2c_setSlaveAddress(0x68); bcm2835_i2c_set_baudrate(10000); printf("DS3231 Test Program ...\n\n"); pcf8563SetTime(); while(1) { pcf8563ReadTime(); buf[0] = buf[0]&0x7F; //sec buf[1] = buf[1]&0x7F; //min buf[2] = buf[2]&0x3F; //hour buf[3] = buf[3]&0x07; //week buf[4] = buf[4]&0x3F; //day buf[5] = buf[5]&0x1F; //mouth //year/month/day printf("20%02x/%02x/%02x ",buf[6],buf[5],buf[4]); //hour:minute/second printf("%02x:%02x:%02x ",buf[2],buf[1],buf[0]); //weekday printf("%s\n",str[(unsigned char)buf[3]]); bcm2835_delay(1000); } bcm2835_i2c_end(); bcm2835_close(); return 0; }
[/codesyntax]
Save the file as “ds3231.c”. Compile and run with:
gcc -Wall ds3231.c -o ds3231-lbcm2835 sudo ./ds3231
Python example
[codesyntax lang=”python”]
#!/usr/bin/python # -*- coding: utf-8 -*- import smbus import time address = 0x68 register = 0x00 #sec min hour week day mout year NowTime = [0x00,0x00,0x22,0x06,0x27,0x12,0x19] w = ["SUN","Mon","Tues","Wed","Thur","Fri","Sat"]; #/dev/i2c-1 bus = smbus.SMBus(1) def ds3231SetTime(): bus.write_i2c_block_data(address,register,NowTime) def ds3231ReadTime(): return bus.read_i2c_block_data(address,register,7); ds3231SetTime() while 1: t = ds3231ReadTime() t[0] = t[0]&0x7F #sec t[1] = t[1]&0x7F #min t[2] = t[2]&0x3F #hour t[3] = t[3]&0x07 #week t[4] = t[4]&0x3F #day t[5] = t[5]&0x1F #mouth print("20%x/%02x/%02x %02x:%02x:%02x %s" %(t[6],t[5],t[4],t[2],t[1],t[0],w[t[3]-1])) time.sleep(1)
[/codesyntax]
Save the file as “ds3231.py” and execute it with:
sudo python ds3231.py
C example using WiringPi
[codesyntax lang=”cpp”]
#include <wiringPi.h> #include <wiringPiI2C.h> #include <stdio.h> #define DS3231_Address 0x68 //seconds,minutes,hours,weekdays,days,months,yeas char buf[]={0x00,0x00,0x22,0x06,0x27,0x12,0x19}; char *str[] ={"SUN","Mon","Tues","Wed","Thur","Fri","Sat"}; int fd,i; void pcf8563SetTime() { for(i = 0;i < 7;i++) { wiringPiI2CWriteReg8(fd,i,buf[i]); } } void pcf8563ReadTime() { for(i = 0;i < 7;i++) { buf[i] = (char)wiringPiI2CReadReg8(fd,i); } } int main(int argc, char **argv) { if(wiringPiSetup() < 0)return 1; fd = wiringPiI2CSetup(DS3231_Address); printf("DS3231 Test Program ...\n\n"); pcf8563SetTime(); while(1) { pcf8563ReadTime(); buf[0] = buf[0]&0x7F; //sec buf[1] = buf[1]&0x7F; //min buf[2] = buf[2]&0x3F; //hour buf[3] = buf[3]&0x07; //week buf[4] = buf[4]&0x3F; //day buf[5] = buf[5]&0x1F; //mouth //year/month/day printf("20%02x/%02x/%02x ",buf[6],buf[5],buf[4]); //hour:minute/second printf("%02x:%02x:%02x ",buf[2],buf[1],buf[0]); //weekday printf("%s\n",str[(unsigned char)buf[3]]); delay(1000); } return 0; }
[/codesyntax]
Save the file as “ds3231.c”. Compile and run with:
gcc -Wall ds3231.c -o ds3231-lbcm2835 -lwiringPi sudo ./ds3231