Arduino I2C + DS1307实时时钟#
https://www.cnblogs.com/zlbg/p/4227428.html
主要特性#
DS1307是Maxim的串行、I2C实时时钟芯片。主要特性有:
工作电压:主电源电压4.5~5.5V,电池电压2.0~3.5V
功耗:电池供电、备份模式时<500nA
接口:I2C,最大速率100kbps
可编程方波输出
电源自动切换、失效检测
内置56字节大小、支持电池备份的RAM
封装:8-Pin SO/PDIP
管脚定义#
X1、X2: 接32.768kHz晶体,要求晶体负载电容12.5pF
Vcc:主电源,范围4.5~5.5V。当需要对DS1307读写时,需要接Vcc。
VBAT:接电池,范围2.0~3.5V。
GND:地
SDA、SCL:I2C接口数据线、时钟线。
SQW/OUT:方波输出脚、通过写寄存器来使能。
与Arduino的连接#
采用I2C接口与Arduino连接。SQW/OUT脚亦为开漏(open-drain)设计,需要接上拉电阻。
DS1307的VCC脚接Arduino UNO的5V;GND脚接Arduino UNO的GND;SDA脚接Arduino UNO的A4(SDA);SCL脚接Arduino UNO的A5(SCL)。
功能调试#
写寄存器时,先写入寄存器指针(Register pointer),之后依次写入寄存器内容。每写入一个字节,Register pointer都自动加一。
读寄存器时,也是先写入Register pointer,之后发Sr(Repeated start),依次读出寄存器内容。同样的,每读出一个字节,Register pinter都自动加一。
测试代码#
首先设置DS1307时间。代码中timeDec数组保存的是当前时间,根据实际调整。
/*
real time clock using DS1307
function: set the time
*/
#include <Wire.h>
#define ADDRESS_DS1307 0x68
byte timeDec[] = {15, 1, 15, 5, 19, 20, 0};
byte timeBcd[] = {0, 0, 0, 0, 0, 0, 0};
//time = {year, month, date, day, hours, minutes, seconds};
void setup()
{
Wire.begin();
Serial.begin(9600);
//convert decimal to BCD code
int i;
for (i = 0; i < 7; i++)
{
timeBcd[i] = DecToBcd(timeDec[i]);
}
//set the time
Wire.beginTransmission(ADDRESS_DS1307);
Wire.write(0x00);
for (i = 0; i < 7; i++)
{
Wire.write(timeBcd[6-i]);
}
Wire.endTransmission();
Serial.println("Time has been set.");
}
void loop()
{
delay(4000);
}
// Convert normal decimal numbers to binary coded decimal
byte DecToBcd(byte val)
{
byte res;
if ((val <= 99) && (val >= 0))
{
res = ((val/10)<<4) | (val%10);
}
else
{
res = 0;
Serial.println("Error");
}
return res;
}
// Convert binary coded decimal to normal decimal numbers
byte BcdToDec(byte val)
{
byte res;
if (val <= 0x99)
{
res = (val >> 4)*10 + (val & 0x0F);
}
else
{
res = 0;
Serial.println("Error");
}
return res;
}
之后可以向DS1307获取实时时间。
/*
real time clock using DS1307
function: read the time
*/
#include <Wire.h>
#define ADDRESS_DS1307 0x68
byte timeBcd[] = {0, 0, 0, 0, 0, 0, 0};
//time = {year, month, date, day, hours, minutes, seconds};
void setup()
{
Wire.begin();
Serial.begin(9600);
}
void loop()
{
//read the time
Wire.beginTransmission(ADDRESS_DS1307);
Wire.write(0x00);
Wire.endTransmission();
Wire.requestFrom(ADDRESS_DS1307, 7);
if (Wire.available() >= 7)
{
for (int i = 0; i < 7; i++)
{
timeBcd[6-i] = Wire.read();
}
}
//print
Serial.print("20"); Serial.print(timeBcd[0], HEX); Serial.print("/");
Serial.print(timeBcd[1], HEX); Serial.print("/"); Serial.print(timeBcd[2], HEX);
Serial.print(" "); Serial.print(BcdToDay(timeBcd[3])); Serial.print(" ");
Serial.print(timeBcd[4], HEX); Serial.print(":");
Serial.print(timeBcd[5], HEX); Serial.print(":");
Serial.print(timeBcd[6], HEX); Serial.println();
delay(1000);
}
// Convert binary coded decimal to day
String BcdToDay(byte val)
{
String res;
switch(val)
{
case 1: res = "Sunday"; break;
case 2: res = "Monday"; break;
case 3: res = "Tuesday"; break;
case 4: res = "Wednesday"; break;
case 5: res = "Thursday"; break;
case 6: res = "Friday"; break;
case 7: res = "Saturday"; break;
default: res = "Error!";
}
return res;
}
程序运行后,通过串口打印当前时间如下图。
通过设置控制寄存器,可以设置SQW/OUT管脚输出高电平、低电平或某个频率的方波。方波支持的频率有1Hz、4.096kHz、8.192kHz、32.768kHz。以下代码设置的频率为32.768kHz。
View Code
与示波器测试的信号图形相符。
参考资料#
Maxim - DS1307 64x8、串行、I²C实时时钟 Tutorial – Using DS1307 and DS3231 Real-time Clock Modules with Arduino Digital Clock with Arduino and DS1307 Assemble an Adafruit DS1307 Real Time Clock Kit