I²串行实时时钟与微控制器的接口

摘要：本应用笔记提供了Dallas I²C接口实时时钟的通用硬件配置和软件例程。本例程适用于采用BCD码时间和日期格式的RTC。


引脚配置

说明

本应用笔记描述了Dallas I²C串行接口实时时钟(RTC)的通用硬件配置，并提供了基本通信软件例程。这些器件包括BCD格式的I²C时钟：DS1307、DS1337、DS1338、DS1339和DS1340。如果对电路进行某些修改，为CLK输入引脚提供数字时钟信号(32,768Hz、8,192Hz、60Hz或50Hz)，还可支持DS1375。本范例中使用了DS2250微控制器，软件为C语言程序。

示意图如图1所示，图中给出了DS1340的连接方式。对于其它型号的RTC，可能需要修改电路。例如：DS1337，用中断输出替代了备用电池输入端。对于低电压RTC，需要用适当的低电压微控制器替代DS2250/DS5000。图2给出了软件清单。#定义说明用来表示特定器件有条件的编译代码。本例程用于DS1307。编译代码之前，用于DS1307的#定义说明应该用正确的器件代替。


放大图形
图1. DS1340和微控制器电路示意图

图2. 软件清单

/********************************************************************//* DEMO1307.c *//* program example for DS1307, DS1337/38/39/40 *//********************************************************************/#include <stdio.h> /* Prototypes for I/O functions */#include <DS5000.h> /* Register declarations for DS5000 *//***************************** Defines *****************************/#define ACK 0#define NACK 1#define ADDRTC 0xd0 /* I²C slave address */#define DS1307 /* compile directive, modify as required *//************************* bit definitions *************************/sbit scl = P0^0; /* I²C pin definitions */sbit sda = P0^1;sbit sqw = P3^2; /* pin function depends upon device *//* General Notes: Define one device to compile options for that device. *//* Will not compile correctly if no device is defined. Not all options *//* for each device are supported. There is no error checking for data *//* entry. Defines may not remove all code that is not relevant to the *//* device. This example was written for an 8051-type micro, the DS2250/ *//* DS5000. The program must be modified to work properly on typical *//* 8051 variants (i.e. assign I²C bus to unused port pins). This *//* program is for example only and is not supported by Dallas Maxim */void I²C_start();void I²C_stop();void I²C_write(unsigned char d);uchar I²C_read(uchar);void readbyte();void writebyte();void initialize();void disp_clk_regs(uchar);void burstramwrite(uchar);void burstramread();void alrm_int();void alrm_read();void tc_setup();/* global variables */uchar sec, min, hr, dy, dt, mn, yr;void I²C_start() /* ----------------------------------------------- */{ sda = 1; scl = 1; /* Initiate start condition */ sda = 0;}void I²C_stop() /* ----------------------------------------------- */{ sda = 0; sda = 0; sda = 0; sda = 0; /* Initiate stop condition */ scl = 1; scl = 1; sda = 1;}void I²C_write(uchar d) /* ----------------------------- */{uchar i; scl = 0; for (i = 1; i <= 8; i++) { sda = (d >> 7); scl = 1; d = d << 1; /* increase scl high time */ scl = 0; } sda = 1; /* Release the sda line */ scl = 0; scl = 1; if(sda) printf("Ack bit missing %02X",(unsigned int)d); scl = 0;}uchar I²C_read(uchar b) /* ----------------------------------- */{uchar d, i; sda = 1; /* Let go of sda line */ scl = 0; for (i = 1; i <= 8; i++) /* read the msb first */ { scl = 1; d = d << 1; d = d | (unsigned char)sda; scl = 0; } sda = b; /* Hold sda low for acknowledge */ scl = 0; scl = 1; if(b == NACK) sda = 1; /* sda = 1 if next cycle is reset */ scl = 0; sda = 1; /* Release the sda line */ return d;}void readbyte() /* -- read one byte of data from the specified address -- */{uchar Add; printf("ADDRESS: "); /* Get Address */ scanf("%bx", &Add); I²C_start(); I²C_write(ADDRTC); I²C_write(Add); I²C_start(); I²C_write(ADDRTC | 1); printf("%2bx", I²C_read(NACK) ); I²C_stop();}void writebyte() /* -- write one byte of data to the specified address -- */{uchar Add;uchar Data; printf("Address: "); /* Get Address */ scanf("%bx", &Add); printf("DATA: "); scanf("%bx", &Data); /* and data */ I²C_start(); I²C_write(ADDRTC); I²C_write(Add); I²C_write(Data); I²C_stop();}void initialize() /* -- initialize the time and date using entries from stdin -- *//* Note: NO error checking is done on the user entries! */{uchar yr, mn, dt, dy, hr, min, sec, day; I²C_start(); /* The following Enables the Oscillator */ I²C_write(ADDRTC); /* address the part to write */ I²C_write(0x00); /* POSTTTION the address pointer to 0 */ I²C_write(0x00); /* write 0 to the seconds register, clear the CH bit */ I²C_stop(); printf("Enter the year (0-99): "); scanf("%bx", &yr); printf("Enter the month (1-12): "); scanf("%bx", &mn); printf("Enter the date (1-31): "); scanf("%bx", &dt); printf("Enter the day (1-7): "); scanf("%bx", &dy); printf("Enter the hour (1-23): "); scanf("%bx", &hr); hr = hr & 0x3f; /* force clock to 24 hour mode */ printf("Enter the minute (0-59): "); scanf("%bx", &min); printf("Enter the second (0-59): "); scanf("%bx", &sec); I²C_start(); I²C_write(ADDRTC); /* write slave address + write */ I²C_write(0x00); /* write register address, 1st clock register */ I²C_write(sec); I²C_write(min); I²C_write(hr); I²C_write(dy); I²C_write(dt); I²C_write(mn); I²C_write(yr);#if defined DS1307 || defined DS1338{ I²C_write(0x10); /* enable sqwe, 1Hz output */}#elif defined DS1337 || defined DS1339{ I²C_start(); I²C_write(ADDRTC); /* write slave address + write */ I²C_write(0x0e); /* write register address, control register */ I²C_write(0x20); /* enable osc, bbsqi */ I²C_write(0); /* clear OSF, alarm flags */ /* could enable trickle charger here */}#elif defined DS1340{ I²C_write(0x10); /* enable sqwe, 1Hz output */ I²C_start(); /* address pointer wraps at 7, so point to flag register */ I²C_write(ADDRTC); /* write slave address + write */ I²C_write(0x09); /* write register address, control register */ I²C_write(0); /* clear OSF */}#endif I²C_stop();}void disp_clk_regs(uchar prv_sec) /* ----------------------------------------- */{uchar Sec, Min, Hrs, Dte, Mon, Day, Yr, mil, pm; printf("Yr Mn Dt Dy Hr:Mn:Sc"); while(!RI) /* Read & Display Clock Registers */ { I²C_start(); I²C_write(ADDRTC); /* write slave address + write */ I²C_write(0x00); /* write register address, 1st clock register */ I²C_start(); I²C_write(ADDRTC | 1); /* write slave address + read */ Sec = I²C_read(ACK); /* starts w/last address stored in register pointer */ Min = I²C_read(ACK); Hrs = I²C_read(ACK); Day = I²C_read(ACK); Dte = I²C_read(ACK); Mon = I²C_read(ACK); Yr = I²C_read(NACK); I²C_stop(); if(Hrs & 0x40) mil = 0; else mil = 1; if(Sec != prv_sec) /* display every time seconds change */ { if(mil) { printf("%02bX/%02bX/%02bX %2bX", Yr, Mon, Dte, Day); printf(" %02bX:%02bX:%02bX", Hrs, Min, Sec); } else { if(Hrs & 0x20) pm = 'A'; else pm = 'P'; Hrs &= 0x1f; /* strip mode and am/pm bits */ printf("%02bx/%02bx/%02bx %02bx", Yr, (Mon & 0x1f), Dte, Day); printf(" %02bx:%02bx:%02bx %cM", Hrs, Min, Sec, pm); } } if(prv_sec == 0xfe) return; prv_sec = Sec; } RI = 0; /* Swallow keypress before exiting */}void burstramwrite(uchar Data) /* -------- fill RAM with data -------- */{uchar j; I²C_start(); I²C_write(ADDRTC); /* write slave address + write */ I²C_write(0x08); /* write register address, 1st RAM LOCAIION */ for (j = 0; j < 56; j++) /* write until the pointer wraps around */ { I²C_write(Data); } I²C_stop();}void burstramread() /* ----------------------------------------- */{uchar j; I²C_start(); I²C_write(ADDRTC); /* write slave address + write */ I²C_write(8); /* write register address, 1st RAM LOCAIION -1*/ I²C_start(); I²C_write(ADDRTC | 1); /* write slave address + read */ for (j = 0; j < 56; j++) { if(!(j % 16)) printf("%02bX ", j); printf("%02bX ", I²C_read(ACK) ); } I²C_read(NACK); I²C_stop();}void alrm_int() /* ----- initialize alarm registers ------ */{uchar M, Sec, Min, Hr, DyDt; printf("1-Alarm each second2-Alarm match=sec3-Alarm match=sec+min"); printf("4-Alarm match=sec+min+hr5-Alarm match=sec+min+hr+date"); printf("6-Alarm match=sec+min+hr+dayEnter selection: "); M = _getkey(); /* Note-No error checking is done on entries! */ switch(M) { case '1': M = 0xf; break; case '2': M = 0xe; break; case '3': M = 0xc; break; case '4': M = 8; break; case '5': M = 0; break; case '6': M = 0x40; break; } if(M & 0x40) { printf("Enter the day (1-7): "); scanf("%bx", &DyDt); } else { printf("Enter the date (1-31): "); scanf("%bx", &DyDt); } printf("Enter the hour (1-23): "); scanf("%bx", &Hr); printf("Enter the minute (0-59): "); scanf("%bx", &Min); printf("Enter the second (0-59): "); scanf("%bx", &Sec); if( (M & 1) ) Sec |= 0x80; if( ((M >> 1) & 1) ) Min |= 0x80; if( ((M >> 2) & 1) ) Hr |= 0x80; if( ((M >> 3) & 1) ) DyDt |= 0x80; if(M & 0x40) DyDt |= 0x40; I²C_start(); I²C_write(ADDRTC); /* write slave address + write */ I²C_write(7); /* write register address */ I²C_write(Sec); I²C_write(Min); I²C_write(Hr); I²C_write(DyDt); I²C_start(); I²C_write(ADDRTC); /* write slave address + write */ I²C_write(0x0e); /* write register address */ I²C_write(5); /* enable interrupts, alarm 1 */ I²C_stop();}void alrm_read() /* ----- read alarm registers ------ */{uchar Sec, Min, Hr, DyDt; I²C_start(); I²C_write(ADDRTC); /* write slave address + write */ I²C_write(7); /* write register address */ I²C_start(); I²C_write(ADDRTC | 1); /* write slave address + read */ Sec = I²C_read(ACK); Min = I²C_read(ACK); Hr = I²C_read(ACK); DyDt = I²C_read(NACK); printf("Alarm 1: %02bx %02bx %02bx %02bx", Sec, Min, Hr, DyDt);}void tc_setup() /* ---- trickle charger set up routine ---- */{uchar M, val;#if defined DS1339 #define TC 0x10 /* address for DS1339 trickle charge register */#else #define TC 0x08 /* address for DS1340 trickle charge register */#endif printf("Enable Trickle Charger (Y/N)? "); M = _getkey(); if(M == 'Y' || M == 'y') { printf("1-250 ohm res2-2K res=sec3-4K res"); M = _getkey(); /* Note-No error checking is done on entries! */ switch(M) { case '1': val = 1; break; case '2': val = 2; break; case '3': val = 3; break; } printf("1-no diode2-1 diode"); M = _getkey(); /* Note-No error checking is done on entries! */ switch(M) { case '1': val += 4; break; case '2': val += 8; break; } I²C_start(); I²C_write(ADDRTC); /* write slave address + write */ I²C_write(TC); /* write register address */ I²C_write(val | 0xa0); /* enable trickle charger per user input */ I²C_stop(); } else { I²C_start(); I²C_write(ADDRTC); /* write slave address + write */ I²C_write(TC); /* write register address */ I²C_write(0); /* disable trickle charger */ I²C_stop(); } I²C_start(); I²C_write(ADDRTC); /* write slave address + write */ I²C_write(TC); /* write register address */ I²C_start(); I²C_write(ADDRTC | 1); /* write slave address + read */ printf("Trickle Charger: %02bx", I²C_read(NACK) );}main (void) /* ----------------------------------------------------- */{uchar M, M1; sqw = 1; /* set up for read, weak pull-up */ while (1) {#if defined DS1307 printf("DEMO1307 build %s", __DATE__);#elif defined DS1337 printf("DEMO1337 build %s", __DATE__);#elif defined DS1338 printf("DEMO1338 build %s", __DATE__);#elif defined DS1339 printf("DEMO1339 build %s", __DATE__);#elif defined DS1340 printf("DEMO1340 build %s", __DATE__);#endif printf("CI Init RTC CR Read Clock"); printf("BR Byte Read BW Write Byte");#if defined DS1337 || defined DS1339 /* only print if part has alarms */ printf("AI Alarm 1 Int AR Alarm Read");#endif#if defined DS1340 || defined DS1339 /* parts that have trickle charger */ printf("Tc Trickle charger");#endif#if defined DS1307 || defined DS1338 /* only print if part has RAM */ printf("RR RAM Read RW RAM Write");#endif printf("Enter Menu Selection:"); M = _getkey(); switch(M) { case 'A': case 'a': printf("Init or Read: "); M1 = _getkey(); switch(M1) { case 'I': case 'i': alrm_int(); break; case 'R': case 'r': alrm_read(); break; } break; case 'B': case 'b': printf("Read or Write: "); M1 = _getkey(); switch(M1) { case 'R': case 'r': readbyte(); break; case 'W': case 'w': writebyte(); break; } break; case 'C': case 'c': printf("\rEnter Clock Routine to run:C"); M1 = _getkey(); switch(M1) { case 'I': case 'i': initialize(); break; case 'R': case 'r': disp_clk_regs(0x99); break; } break; case 'R': case 'r': printf("\rEnter Ram Routine to run:R"); M1 = _getkey(); switch(M1) { case 'R': case 'r': burstramread(); break; case 'W': case 'w': printf("Enter the data to write: "); scanf("%bx", &M1); burstramwrite(M1); break; } break; case 'T': case 't': tc_setup(); break; } }}

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