Philips PCF8583 RTC (I2C) - Writing and Reading Time
/* 8583_1.C, Flashlite V25
**
** Writes a base time and date to clock. Reads clock about every
** second and displays on terminal.
**
** Note that time and date data is stored in BCD. In this routine
** natural binary is converted to BCD when writing to the PCF8583. When
** reading data, the quanties are converted to natural binary.
**
** Flashlite V25 PCF8583
**
** P2.1 ------------------- SCL (term 6) ----- To Other
** P2.0 ------------------- SDA (term 5) ----- I2C Devices
**
** I2C address is 0xa0 or 0xa2 depending on strapping of A0 (terminal 3)
** In this example, A0 is at ground.
**
** copyright, Peter H. Anderson, Onya Barnes, Baltimore, MD, October, '00
*/
#include <stdio.h>
#include <dos.h>
typedef unsigned char byte;
#define SEG 0xf000
#define P2_OFFSET 0xff10
#define PM2_OFFSET 0xff11
#define PMC2_OFFSET 0xff12
struct Time
{
byte hr;
byte mi;
byte se;
};
struct Date
{
byte yr;
byte mo;
byte da;
byte weekday;
};
/* routines used for PCF8583 */
void _8583_configure_control_register(byte control_reg);
void _8583_write_clock(struct Time *p_t, struct Date *p_d);
void _8583_read_clock(struct Time *p_t, struct Date *p_d);
void _8583_display_date_time(struct Time *p_t, struct Date *p_d);
void put_dec_byte(byte v, byte places);
byte to_BCD(byte natural_binary);
byte to_natural_binary(byte BCD);
/*common i2c routines*/
byte i2c_in_byte(void);
void i2c_out_byte(byte o_byte);
void i2c_nack(void);
void i2c_ack(void);
void i2c_start(void);
void i2c_stop(void);
void i2c_high_sda(void);
void i2c_low_sda(void);
void i2c_high_scl(void);
void i2c_low_scl(void);
/* note global */
byte far *p2, far *pm2, far *pmc2;
byte dirs2, outs2;
void main(void)
{
struct Time t_base, t;
struct Date d_base, d;
clrscr();
p2=MK_FP(SEG, P2_OFFSET);
pm2=MK_FP(SEG, PM2_OFFSET);
pmc2=MK_FP(SEG, PMC2_OFFSET);
dirs2=0xff;
*pmc2=0x00;
*pm2=dirs2;
t_base.hr=23; t_base.mi=59; t_base.se=00;
d_base.yr=3; d_base.mo=2; d_base.da=28; d_base.weekday=1;
/* Note that year is 0 through 3. Thus, if the base year is 2000
** this is Feb 28, 2003, Monday.
*/
_8583_display_date_time(&t_base, &d_base);
_8583_configure_control_register(0x00); /* 32.768 kHz, no alarm */
_8583_write_clock(&t_base, &d_base);
while(!kbhit())
{
_8583_read_clock(&t, &d);
_8583_display_date_time(&t, &d);
delay(1000);
}
}
void _8583_write_clock(struct Time *p_t, struct Date *p_d)
{
/* Note that most sig bit of hours is 12/24 hour format
** 4 year is in bits 7 and 6 of 0x05. Lower six bits are day in BCD
** Location 0x06. Weeks day is in bits 7, 6, 5 and month in lower
** five bits.
*/
byte v;
i2c_start();
i2c_out_byte(0xa0);
i2c_nack();
i2c_out_byte(0x01); /* address of first write */
i2c_nack();
i2c_out_byte(0x00); /* hundreths of a second */
i2c_nack();
v = to_BCD(p_t->se);
i2c_out_byte(v);
i2c_nack();
v = to_BCD(p_t->mi);
i2c_out_byte(v); /* location 0x03 */
i2c_nack();
v = to_BCD(p_t->hr);
i2c_out_byte(v);
/* 24 hour format - 0x80 for 12 hour time */
i2c_nack();
v = to_BCD(p_d->da);
i2c_out_byte((p_d->yr << 6) | v);
/* YY TT UUUU */
i2c_nack();
v = to_BCD(p_d->mo);
i2c_out_byte(
(p_d->weekday << 5) | v );
/* DDD T UUUU */
i2c_nack();
i2c_stop();
}
void _8583_read_clock(struct Time *p_t, struct Date *p_d)
{
byte v;
i2c_start();
i2c_out_byte(0xa0);
i2c_nack();
i2c_out_byte(0x02); /* begin with seconds */
i2c_nack();
i2c_start();
i2c_out_byte(0xa1);
i2c_nack();
v = i2c_in_byte() & 0x7f;
p_t->se = to_natural_binary(v);
i2c_ack();
v = i2c_in_byte();
p_t->mi = to_natural_binary(v);
i2c_ack();
v = i2c_in_byte() & 0x3f;
p_t->hr = to_natural_binary(v);
i2c_ack();
v = i2c_in_byte();
p_d->yr = v >> 6; /* year is in two most sig bits */
v = v & 0x3f; /* day in lower six bits */
p_d->da = to_natural_binary(v);
i2c_ack();
v = i2c_in_byte();
p_d->weekday = v >> 5;
v = v & 0x1f;
p_d->mo = to_natural_binary(v);
i2c_nack();
i2c_stop();
}
void _8583_configure_control_register(byte control_reg)
{
i2c_start();
i2c_out_byte(0xa0);
i2c_nack();
i2c_out_byte(0x00); /* control register address */
i2c_nack();
i2c_out_byte(control_reg);
i2c_nack();
i2c_stop();
}
void _8583_display_date_time(struct Time *p_t, struct Date *p_d)
{
/*assumes base year of 2000*/
printf("%0.2d/%0.2d/%0.2d\n", p_d->yr +00, p_d->mo, p_d->da);
printf("%.02:%0.2d:%0.2d\n", p_t->hr, p_t->mi, p_t->se);
printf("%d\n", p_d->weekday);
}
byte to_BCD(byte natural_binary)
{
return ( ((natural_binary/10) << 4) + natural_binary%10 );
}
byte to_natural_binary(byte BCD)
{
return( ((BCD >> 4) * 10) + (BCD & 0x0f) );
}
/* Common I2C Routines*/
byte i2c_in_byte(void)
{
byte i_byte=0, n;
i2c_high_sda();
for (n=0; n<8; n++)
{
i2c_high_scl();
if (*(p2) & 0x01)
{
i_byte = (i_byte << 1) | 0x01; /* msbit first */
}
else
{
i_byte = i_byte << 1;
}
i2c_low_scl();
}
return(i_byte);
}
void i2c_out_byte(byte o_byte)
{
byte n;
for(n=0; n<8; n++)
{
if(o_byte&0x80)
{
i2c_high_sda();
}
else
{
i2c_low_sda();
}
i2c_high_scl();
i2c_low_scl();
o_byte = o_byte << 1;
}
i2c_high_sda();
}
void i2c_nack(void)
{
i2c_high_sda(); /*data at one*/
i2c_high_scl(); /*clock pulse*/
i2c_low_scl();
}
void i2c_ack(void)
{
i2c_low_sda(); /*bring data low and clock*/
i2c_high_scl();
i2c_low_scl();
i2c_high_sda();
}
void i2c_start(void)
{
i2c_low_scl();
i2c_high_sda();
i2c_high_scl(); /* bring SDA low while SCL is high*/
i2c_low_sda();
i2c_low_scl();
}
void i2c_stop(void)
{
i2c_low_scl();
i2c_low_sda();
i2c_high_scl();
i2c_high_sda(); /*bring SDA high while SCL is high*/
/*idle is SDA high and SCL high*/
}
void i2c_high_sda(void)
{
dirs2 = dirs2 | 0x01;
*pm2 = dirs2;
#ifdef D /* used for debugging */
printf("SDA_HIGH %x\n", dirs2);
delay(500);
#endif
}
void i2c_low_sda(void)
{
outs2 = outs2 & (~0x01); /* zero the output pin */
*p2 = outs2;
dirs2 = dirs2 & (~0x01); /* and output */
*pm2 = dirs2;
#ifdef D
printf("SDA_LOW %x\n", dirs2);
delay(500);
#endif
}
void i2c_high_scl(void)
{
dirs2 = dirs2 | 0x02; /* bring SCL to high impedance */
*pm2 = dirs2;
#ifdef D
printf("SCL_HIGH %x\n", dirs2);
delay(500);
#endif
}
void i2c_low_scl(void)
{
outs2 = outs2 & (~0x02);
*p2 = outs2; /* zero the output pin */
dirs2 = dirs2 & (~0x02); /* and output */
*pm2 = dirs2;
#ifdef D
printf("SCL_LOW %x\n", dirs2);
delay(500);
#endif
}