--- /dev/null
+/*-----------------------------------------------------------------------*/
+/* DS1202 and DS1302 Serial Real Time Clock driver */
+/* 2014-12-30 Will Sowerbutts */
+/*-----------------------------------------------------------------------*/
+
+#include <kernel.h>
+#include <kdata.h>
+#include <stdbool.h>
+#include <printf.h>
+#include <ds1302.h>
+
+static void ds1302_send_byte(uint8_t byte)
+{
+ uint8_t i;
+
+#ifdef DS1302_DEBUG
+ kprintf("ds1302: send byte 0x%x\n", byte);
+#endif
+ /* drive the data pin */
+ ds1302_set_pin_data_driven(true);
+
+ /* clock out one byte, LSB first */
+ for(i=0; i<8; i++){
+ ds1302_set_pin_clk(false);
+ /* for data input to the chip the data must be valid on the rising edge of the clock */
+ ds1302_set_pin_data(byte & 1);
+ byte >>= 1;
+ ds1302_set_pin_clk(true);
+ }
+}
+
+static uint8_t ds1302_receive_byte(void)
+{
+ uint8_t i, b;
+
+ /* tri-state the data pin */
+ ds1302_set_pin_data_driven(false);
+
+ /* clock in one byte, LSB first */
+ b = 0;
+ for(i=0; i<8; i++){
+ ds1302_set_pin_clk(false);
+ b >>= 1;
+ /* data output from the chip is presented on the falling edge of each clock */
+ /* note that output pin goes high-impedance on the rising edge of each clock */
+ if(ds1302_get_pin_data())
+ b |= 0x80;
+ ds1302_set_pin_clk(true);
+ }
+
+ return b;
+}
+
+static uint8_t from_bcd(uint8_t value)
+{
+ return (value & 0x0F) + (10 * (value >> 4));
+}
+
+void ds1302_read_clock(uint8_t *buffer, uint8_t length)
+{
+ uint8_t i;
+ irqflags_t irq = di();
+
+ ds1302_set_pin_ce(true);
+ ds1302_send_byte(0x81 | 0x3E); /* burst read all calendar data */
+ for(i=0; i<length; i++){
+ buffer[i] = ds1302_receive_byte();
+#ifdef DS1302_DEBUG
+ kprintf("ds1302: received byte 0x%x index %d\n", buffer[i], i);
+#endif
+ }
+ ds1302_set_pin_ce(false);
+ irqrestore(irq);
+}
+
+/* define CONFIG_RTC in platform's config.h to hook this into timer.c */
+uint8_t rtc_secs(void)
+{
+ uint8_t buffer;
+ ds1302_read_clock(&buffer, 1); /* read out only the seconds value */
+ return from_bcd(buffer & 0x7F); /* mask off top bit (clock-halt) */
+}
+
+/****************************************************************************/
+/* Code below this point used only once, at startup, so we want it to live */
+/* in the DISCARD segment. sdcc only allows us to specify one segment for */
+/* each source file. This "solution" is a bit (well, very) hacky ... */
+/****************************************************************************/
+static void DISCARDSEG(void) __naked { __asm .area _DISCARD __endasm; }
+
+/* we avoid using 32x32 bit multiply ds1302_read_rtc, because it causes sdcc to pull
+ in a huge __mullong helper -- which is nearly 500 bytes! */
+static uint32_t multiply_8x32(uint8_t a, uint32_t b) __naked /* return a * b */
+{
+ __asm
+ ; WRS -- simple 8x32 multiply routine
+ ; low 16 bits in main registers, high 16 bits in alternate registers
+ ; DE contains b, shifts left, HL contains accumulated result, A contains a, shifts right.
+ ld iy, #0 ; load parameters from stack
+ add iy, sp
+ ld a, 2(iy) ; load a
+ ld e, 3(iy) ; load low 16 bits of b
+ ld d, 4(iy)
+ and a ; clear carry flag
+ sbc hl, hl ; low result = 0
+ exx
+ sbc hl, hl ; high result = 0
+ ld e, 5(iy) ; load high 16 bits of b
+ ld d, 6(iy)
+ exx
+mulgo: ; loop executes at most 8 times (depends on highest bit set in a)
+ or a ; test value of A
+ jr z, muldone ; if A is now zero we are done
+ rra ; shift A right one bit, rotate low bit into carry flag
+ jr nc, mulnext ; if low bit was zero, skip the accumulate
+ add hl, de ; add low 16 bits
+ exx
+ adc hl, de ; add high 16 bits
+ exx
+mulnext:
+ and a ; clear carry flag
+ rl e ; double low 16 bits
+ rl d
+ exx
+ rl e ; double high 16 bits
+ rl d
+ exx
+ jr mulgo ; go again
+muldone:
+ exx ; get the high 16 bits into DE
+ push hl
+ exx
+ pop de
+ ret ; return with 32-bit result in DEHL, as per sdcc callng convention
+ __endasm;
+ a; b; /* squelch compiler warning */
+}
+
+static const uint16_t mktime_moffset[12] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
+
+uint32_t ds1302_read_rtc(void)
+{
+ uint32_t ret;
+ uint8_t buffer[7];
+ uint8_t year, month, day, hour, minute, second;
+
+ ds1302_read_clock(buffer, 7); /* read all calendar data */
+
+ year = from_bcd(buffer[6]);
+ month = from_bcd(buffer[4] & 0x1F);
+ day = from_bcd(buffer[3] & 0x3F);
+ if(buffer[2] & 0x80) /* AM/PM 12-hour mode */
+ hour = from_bcd(buffer[2] & 0x1F) + (buffer[2] & 0x20 ? 12 : 0);
+ else /* sensible 24-hour mode */
+ hour = from_bcd(buffer[2] & 0x3F);
+ minute = from_bcd(buffer[1]);
+ second = from_bcd(buffer[0] & 0x7F);
+
+ if(year < 70)
+ year += 100;
+
+ /* following code is based on utc_mktime() from ELKS
+ https://github.com/jbruchon/elks/blob/master/elkscmd/sh_utils/date.c */
+
+ /* uses zero-based month index */
+ month--;
+
+ /* calculate days from years */
+ ret = multiply_8x32(year - 70, 365);
+
+ /* count leap days in preceding years */
+ ret += ((year - 69) >> 2);
+
+ /* calculate days from months */
+ ret += mktime_moffset[month];
+
+ /* add in this year's leap day, if any */
+ if (((year & 3) == 0) && (month > 1)) {
+ ret ++;
+ }
+
+ /* add in days in this month */
+ ret += (day - 1);
+
+ /* convert to hours */
+ ret = multiply_8x32(24, ret);
+ ret += hour;
+
+ /* convert to minutes */
+ ret = multiply_8x32(60, ret);
+ ret += minute;
+
+ /* convert to seconds */
+ ret = multiply_8x32(60, ret);
+ ret += second;
+
+ /* return the result */
+ return ret;
+}
+
+void ds1302_init(void)
+{
+ time_t tod;
+
+ /* initialise the hardware into a sensible state */
+ ds1302_set_pin_data_driven(true);
+ ds1302_set_pin_data(false);
+ ds1302_set_pin_ce(false);
+ ds1302_set_pin_clk(false);
+
+ tod.high = 0; /* until 2106 */
+ tod.low = ds1302_read_rtc();
+ wrtime(&tod);
+}
public / FUZIX.git / commitdiff