查看“树莓派系列教程：RTC”的源代码



树莓派本身没有RTC功能，若树莓派不联网则无法从网络获取正确时间，Pioneer 600扩展板上面带有高精度RTC时钟DS3231芯片，可解决这个问题。
一、配置RTC
<!--[if !supportLists]-->1、 <!--[endif]-->修改配置文件
<syntaxhighlight lang="python">
sudo vi /boot/config.txt</syntaxhighlight>
添加RTC设备ds3231
<syntaxhighlight lang="python">
dtoverlay=i2c-rtc,ds3231</syntaxhighlight>
重启树莓派生效设置，开机后可以运行lsmod命令查看时候有rtc-1307模块。
（注：ds3231为i2c控制，故应打开树莓派I2C功能）


<!--[if !supportLists]-->2、 <!--[endif]-->读取RTC时钟，
<syntaxhighlight lang="python">
sudo hwclock –r</syntaxhighlight>
读取系统时间
<syntaxhighlight lang="python">
date </syntaxhighlight>
<!--[if !supportLists]-->3、 <!--[endif]-->设置RTC时间
<syntaxhighlight lang="python">
sudo hwclock –set –date=”2015/08/12 18:00:00”</syntaxhighlight>
<!--[if !supportLists]-->4、 <!--[endif]-->更新RTC时间到系统
<syntaxhighlight lang="python">
sudo hwclock -s</syntaxhighlight>
<!--[if !supportLists]-->5、 <!--[endif]-->读取RTC时间及系统时间
<syntaxhighlight lang="python">
sudo hwclock –r;date</syntaxhighlight>
 

[[File:093948zp5fmg6pmcggnyrp.png]]

二、编程控制
 我们也可以通过I2C编程读写RTC时间，运行i2cdetect –y 1命令我们可以看到下图，我们发现ds3231的i2c地址0x68的位置显示UU,此时ds3231作为树莓派的硬件时钟，不能通过i2c编程控制，必须将刚才配置文件中的设置注释掉才能用。


[[File:094102d1b57ykkf1c4t454.png]]

<syntaxhighlight lang="python">
sudo vi /boot/config.txt</syntaxhighlight> 
找到刚才的设置，在前面加’#’注释掉
<syntaxhighlight lang="python">
#dtoverlay=i2c-rtc,ds3231</syntaxhighlight>
 
重启后再运行i2cdetect –y 1此时发现ds3231可以通过i2c编程控制



[[File:094236i0ng0qs6lxzjcc6q.png]]

1、bcm2835
<syntaxhighlight lang="python">
#include <bcm2835.h>
#include <stdio.h>
#include <unistd.h>

//regaddr,seconds,minutes,hours,weekdays,days,months,yeas
char  buf[]={0x00,0x00,0x00,0x18,0x04,0x12,0x08,0x15};
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("start..........\n"); 
    
    pcf8563SetTime(); 
    while(1)  
    {   
        pcf8563ReadTime();
        buf[0] = buf[0]&amp;0x7F; //sec
        buf[1] = buf[1]&amp;0x7F; //min
        buf[2] = buf[2]&amp;0x3F; //hour
        buf[3] = buf[3]&amp;0x07; //week
        buf[4] = buf[4]&amp;0x3F; //day
        buf[5] = buf[5]&amp;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]-1]);
        bcm2835_delay(1000);
    }

    bcm2835_i2c_end();
    bcm2835_close();

    return 0;
}</syntaxhighlight>
 
编译并执行
<syntaxhighlight lang="python">
gcc –Wall ds3231.c –o ds3231 –lbcm2835
sudo ./ds3231</syntaxhighlight>
 

[[File:094535iw5xhufefuwefii2.png]]

2、python
<syntaxhighlight lang="python">
#!/usr/bin/python
# -*- coding: utf-8 -*-
import smbus
import time

address = 0x68
register = 0x00
#sec min hour week day mout year
NowTime = [0x00,0x00,0x18,0x04,0x12,0x08,0x15]
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]&amp;0x7F  #sec
    t[1] = t[1]&amp;0x7F  #min
    t[2] = t[2]&amp;0x3F  #hour
    t[3] = t[3]&amp;0x07  #week
    t[4] = t[4]&amp;0x3F  #day
    t[5] = t[5]&amp;0x1F  #mouth
    print("20%x/%x/%x %x:%x:%x  %s" %(t[6],t[5],t[4],t[2],t[1],t[0],w[t[3]-1]))
time.sleep(1)</syntaxhighlight>
执行程序
<syntaxhighlight lang="python">
sudo python ds3231.py</syntaxhighlight>

[[File:094535icvpsycgmkk8im57.png]]


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