首页 > 代码库 > Arduino I2C + DS1307实时时钟
Arduino I2C + DS1307实时时钟
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
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
1. 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。
2. 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
1. 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。
1 /* 2 real time clock using DS1307 3 function: set the time 4 */ 5 6 #include <Wire.h> 7 8 #define ADDRESS_DS1307 0x68 9 10 byte timeDec[] = {15, 1, 15, 5, 19, 20, 0};11 byte timeBcd[] = {0, 0, 0, 0, 0, 0, 0};12 //time = {year, month, date, day, hours, minutes, seconds};13 14 void setup()15 {16 Wire.begin();17 Serial.begin(9600);18 19 //convert decimal to BCD code20 int i;21 for (i = 0; i < 7; i++)22 {23 timeBcd[i] = DecToBcd(timeDec[i]);24 }25 26 //set the time27 Wire.beginTransmission(ADDRESS_DS1307);28 Wire.write(0x00);29 for (i = 0; i < 7; i++)30 {31 Wire.write(timeBcd[6-i]);32 }33 Wire.endTransmission();34 35 Serial.println("Time has been set.");36 37 }38 39 void loop()40 {41 delay(4000);42 }43 44 // Convert normal decimal numbers to binary coded decimal45 byte DecToBcd(byte val)46 {47 byte res;48 if ((val <= 99) && (val >= 0))49 {50 res = ((val/10)<<4) | (val%10);51 }52 else53 {54 res = 0;55 Serial.println("Error");56 }57 return res;58 }59 // Convert binary coded decimal to normal decimal numbers60 byte BcdToDec(byte val)61 {62 byte res;63 if (val <= 0x99)64 {65 res = (val >> 4)*10 + (val & 0x0F);66 }67 else68 {69 res = 0;70 Serial.println("Error");71 }72 return res;73 }
2. 之后可以向DS1307获取实时时间。
1 /* 2 real time clock using DS1307 3 function: read the time 4 */ 5 6 #include <Wire.h> 7 8 #define ADDRESS_DS1307 0x68 9 10 byte timeBcd[] = {0, 0, 0, 0, 0, 0, 0};11 //time = {year, month, date, day, hours, minutes, seconds};12 13 void setup()14 {15 Wire.begin();16 Serial.begin(9600);17 }18 19 void loop()20 {21 //read the time22 Wire.beginTransmission(ADDRESS_DS1307);23 Wire.write(0x00);24 Wire.endTransmission();25 Wire.requestFrom(ADDRESS_DS1307, 7);26 if (Wire.available() >= 7)27 {28 for (int i = 0; i < 7; i++)29 {30 timeBcd[6-i] = Wire.read();31 }32 }33 34 //print35 Serial.print("20"); Serial.print(timeBcd[0], HEX); Serial.print("/");36 Serial.print(timeBcd[1], HEX); Serial.print("/"); Serial.print(timeBcd[2], HEX);37 Serial.print(" "); Serial.print(BcdToDay(timeBcd[3])); Serial.print(" ");38 Serial.print(timeBcd[4], HEX); Serial.print(":");39 Serial.print(timeBcd[5], HEX); Serial.print(":");40 Serial.print(timeBcd[6], HEX); Serial.println();41 42 delay(1000);43 }44 45 46 // Convert binary coded decimal to day47 String BcdToDay(byte val)48 {49 String res;50 switch(val)51 {52 case 1: res = "Sunday"; break;53 case 2: res = "Monday"; break;54 case 3: res = "Tuesday"; break;55 case 4: res = "Wednesday"; break;56 case 5: res = "Thursday"; break;57 case 6: res = "Friday"; break;58 case 7: res = "Saturday"; break;59 default: res = "Error!";60 }61 return res;62 }
程序运行后,通过串口打印当前时间如下图。
3. 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。
1 /* 2 real time clock using DS1307 3 function: output the square-wave 4 */ 5 6 #include <Wire.h> 7 8 #define ADDRESS_DS1307 0x68 9 #define CONTROL_REGISTER 0x0710 11 void setup()12 {13 Wire.begin();14 Serial.begin(9600);15 16 //set the time17 Wire.beginTransmission(ADDRESS_DS1307);18 Wire.write(CONTROL_REGISTER);19 Wire.write(0b00010011); //frequency = 32.768kHz20 Wire.endTransmission();21 22 Serial.println("Square-wave output is enabled.");23 }24 25 void loop()26 {27 delay(4000);28 }
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
Arduino I2C + DS1307实时时钟