Can’t get STC12C5A60S2 to talk to DS1302 RTC

[Wayne]

Hi everybody.  This is my first post on this forum, so please forgive me if I bend a rule or don't use correct formats.  In fact, I'm having trouble figuring out this editor… but that's a problem for another day.

Please feel free to point me toward the forum rules if necessary…

I bought a "development board" on eBay, and have been slowly figuring out how to program it.  But I've hit quite a stumbling block with the DS1302 Real-Time-Clock.  I simply cannot get the code to work.  I started by studying sample codes that I found online (mainly here) and — as best as I can tell — my code should do the same thing.  But it doesn't.  The board is labeled HL-1.  According to the schematic, the "CE" line is on pin P2.4, the CLK line is on pin P2.1, and the I/O line is on pin P2.0.

The chip is an STC12C5A60S2; I've also tried it with an STC89C52RC and it does the same thing (nothing).

I debugged the display logic while figuring out how to interface with the keyboard; I'm am 99.9% certain the problem is in the DS1302 code.  And I can plug numbers into the code and the numbers will display as expected.  It is only when trying to interface with the DS1302 that it displays all zeros.  Thus, all I included in this post is the code to interface with the DS1302.

I would like to use the documentation that came with the board to help out but, alas, it's in Chinese!

If one of you code experts could take a quick look at this and tell me what I did wrong, I will be forever grateful!

Here's the DS1302.h file…

************************************************************************************************************

#ifndef RTC_H
#define RTC_H
#include "bsp_cfg.h"
 
typedef struct
{
    INT8U second;
    INT8U minute;
    INT8U hour;
    INT8U date;
    INT8U month;
    INT8U day;
    INT8U year;
} Time_Date;
 
Time_Date get_time_1302(void);
 
void set_time_1302(Time_Date dt);

void init_1302(void);
 
#endif

***********************************************************************************************************

and here's the DS1302.c code…

***********************************************************************************************************

#include "DS1302 RTC.h"

sbit ACC0 = ACC^0;
sbit ACC7 = ACC^7;
sbit CE_1302 = P2^4;  // 1302 CE bit
sbit SCLK_1302 = P2^1; // 1302 Strobe Clock bit
sbit IO_1302 = P2^0;  // 1302 IO bit
 
#define BURST_READ_1302 0xbf
#define BURST_WRITE_1302 0xbe
#define SECONDS_READ_1302 0x81
#define SECONDS_WRITE_1302 0x80
#define HOURS_READ_1302 0x85
#define HOURS_WRITE_1302 0x84
#define WP_WRITE_1302 0x8e
 
static INT8U read_byte(void)
{
  INT8U i;

 ACC = 0;
 for (i = 8; i > 0; i–)
 {
  ACC = ACC >> 1;
  SCLK_1302 = 1;
  ACC7 = IO_1302;
  SCLK_1302 = 0;
 }
 return ACC;
}
 
static void write_byte(INT8U byte)
{
  INT8U i;
 
 ACC = byte;
 
  for (i = 0; i < 8; ++i)
 {
  IO_1302 = ACC0;
  SCLK_1302 = 1;
  SCLK_1302 = 0;
  ACC = ACC >> 1;
 }
}
 
Time_Date get_time_1302(void)
{
 Time_Date dt;
 
 SCLK_1302 = 0;
  CE_1302 = 0;
 CE_1302 = 1; 
 write_byte(BURST_READ_1302);
 dt.second = read_byte();
 dt.minute = read_byte();
 dt.hour = read_byte();
 dt.date = read_byte();
 dt.month = read_byte();
 dt.day = read_byte();
 dt.year = read_byte();
 SCLK_1302 = 0;
  CE_1302 = 0;
 CE_1302 = 1; 
 return dt;
}
 
void set_time_1302(Time_Date dt)
{
 SCLK_1302 = 0;
  CE_1302 = 0;
 CE_1302 = 1; 
 write_byte(BURST_WRITE_1302);
 write_byte(dt.second);
 write_byte(dt.minute);
 write_byte(dt.hour);
 write_byte(dt.date);
 write_byte(dt.month);
 write_byte(dt.day);
 write_byte(dt.year);
 write_byte(0);
 SCLK_1302 = 0;
  CE_1302 = 0;
 CE_1302 = 1;
}
 
void init_1302(void)
{
  INT8U byte_second;
  INT8U byte_hour;
 
  //Disable Clock Halt
 SCLK_1302 = 0;
  CE_1302 = 0;
 CE_1302 = 1;
 write_byte(SECONDS_READ_1302);
  byte_second = read_byte();
  SCLK_1302 = 0;
  CE_1302 = 0;
 CE_1302 = 1;
  write_byte(SECONDS_WRITE_1302);
  write_byte(byte_second & 0x7f);
 SCLK_1302 = 0;
  CE_1302 = 0;
 CE_1302 = 1;   
 
  //Set to 24 hour mode
  write_byte(HOURS_READ_1302);
  byte_hour = read_byte();
  SCLK_1302 = 0;
  CE_1302 = 0;
 CE_1302 = 1;
  write_byte(HOURS_WRITE_1302);
  write_byte(byte_hour & 0x7f);
 SCLK_1302 = 0;
  CE_1302 = 0;
 CE_1302 = 1;
 
  //Disable Write Protection
  write_byte(WP_WRITE_1302);
  write_byte(0);
 SCLK_1302 = 0;
  CE_1302 = 0;
 CE_1302 = 1;
}

**********************************************************************************************************

Thank you!

Wayne.

 

[Wayne]

Well… in case anyone was wondering… after much trial and error… it appears to be working.  Time will tell (pun sortof intended).

Here is the code that seems to work.

**********************************************************************************************************

 
#include "DS1302 RTC.h"

sbit ACC0 = ACC^0;
sbit ACC7 = ACC^7;
sbit CE_1302 = P2^4;  // 1302 CE bit
sbit SCLK_1302 = P2^1; // 1302 Strobe Clock bit
sbit IO_1302 = P2^0;  // 1302 IO bit

#define BURST_READ_1302 0xbf
#define BURST_WRITE_1302 0xbe
#define SECONDS_READ_1302 0x81
#define SECONDS_WRITE_1302 0x80
#define HOURS_READ_1302 0x85
#define HOURS_WRITE_1302 0x84
#define WP_WRITE_1302 0x8e
 
static INT8U read_byte(void)
{
  INT8U i, dat;

 dat = 0;
 for (i = 0; i < 8; i++)
 {
  dat = dat >> 1;
  if (IO_1302 == 1)
   dat = dat | 0x80;
  SCLK_1302 = 1;
  SCLK_1302 = 0;
 }
 return dat;
}
 
static void write_byte(INT8U byte)
{
  INT8U i, dat;
 
 dat = byte;
 SCLK_1302 = 0;
  for (i = 0; i < 8; i++)
 {
  IO_1302 = dat & 0x01;
  SCLK_1302 = 1;
  SCLK_1302 = 0;
  dat = dat >> 1;
 }
}
 
Time_Date get_time_1302(void)
{
 Time_Date dt;
 
  CE_1302 = 0;
 SCLK_1302 = 0;
 CE_1302 = 1; 
 write_byte(BURST_READ_1302);
 dt.second = read_byte();
 dt.second = (((dt.second & 0x70) >> 4) * 10) + (dt.second & 0x0f);
 dt.minute = read_byte();
 dt.minute = (((dt.minute & 0x70) >> 4) * 10) + (dt.minute & 0x0f);
 dt.hour = read_byte();
 dt.hour = (((dt.hour & 0x70) >> 4) * 10) + (dt.hour & 0x0f);
 dt.date = read_byte();
 dt.date = (((dt.date & 0x70) >> 4) * 10) + (dt.date & 0x0f);
 dt.month = read_byte();
 dt.month = (((dt.month & 0x70) >> 4) * 10) + (dt.month & 0x0f);
 dt.day = read_byte();
 dt.year = read_byte();
 dt.year = (((dt.year & 0xf0) >> 4) * 10) + (dt.year & 0x0f);
 SCLK_1302 = 1;
  CE_1302 = 0;
 return dt;
}
 
void set_time_1302(Time_Date dt)
{
  CE_1302 = 0;
 SCLK_1302 = 0;
 CE_1302 = 1; 
 write_byte(BURST_WRITE_1302);
 write_byte((((dt.second / 10) << 4) + (dt.second % 10)) & 0x7f);
 write_byte(((dt.minute / 10) << 4) + (dt.minute % 10));
 write_byte((((dt.hour / 10) << 4) + (dt.hour % 10)) & 0x3f);
 write_byte(((dt.date / 10) << 4) + (dt.date % 10));
 write_byte(((dt.month / 10) << 4) + (dt.month % 10));
 write_byte(dt.day);
 write_byte(((dt.year / 10) << 4) + (dt.year % 10));
 write_byte(0);
 SCLK_1302 = 1;
  CE_1302 = 0;
}
 
void init_1302(void)
{
  INT8U byte_second;
  INT8U byte_hour;
 
  //Disable Clock Halt
  CE_1302 = 0;
 SCLK_1302 = 0;
 CE_1302 = 1;
 write_byte(SECONDS_READ_1302);
  byte_second = read_byte();
  SCLK_1302 = 0;
  write_byte(SECONDS_WRITE_1302);
  write_byte(byte_second & 0x7f);
 SCLK_1302 = 1;
 
  //Set to 24 hour mode
  write_byte(HOURS_READ_1302);
  byte_hour = read_byte();
  SCLK_1302 = 0;
  write_byte(HOURS_WRITE_1302);
  write_byte(byte_hour & 0x3f);
 SCLK_1302 = 0;
 
  //Disable Write Protection
  write_byte(WP_WRITE_1302);
  write_byte(0);
 SCLK_1302 = 0;
  CE_1302 = 0;
}

 

**********************************************************************************************************

 

 

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