# HG changeset patch
# User Tero Koskinen <tero.koskinen@iki.fi>
# Date 1461599537 -10800
#      Mon Apr 25 18:52:17 2016 +0300
# Node ID c9ae47eca21dd30bcad214b908259a1e029b098f
# Parent  16a1b4a9af387a7ed8619e0c44207212ba810e6d
Add DS3231 driver.

diff --git a/ds3231.c b/ds3231.c
new file mode 100644
--- /dev/null
+++ b/ds3231.c
@@ -0,0 +1,83 @@
+// Code originally by JeeLabs http://news.jeelabs.org/code/
+// Released to the public domain! Enjoy!
+
+#include <debugio.h>
+#include <stdint.h>
+
+#include "ds3231.h"
+
+static uint8_t bcd2bin (uint8_t val) { return val - 6 * (val >> 4); }
+static uint8_t bin2bcd (uint8_t val) { return val + 6 * (val / 10); }
+
+#define DS3231_ADDRESS  (0x68 << 1)
+#define DS3231_CONTROL  0x0E
+#define DS3231_STATUSREG 0x0F
+
+static CTL_I2C_BUS_t *ds3231_i2c_bus = 0;
+
+int RTC_DS3231_init(CTL_I2C_BUS_t *i2c)
+{
+  ds3231_i2c_bus = i2c;
+
+  return 0;
+}
+
+int RTC_DS3231_now(struct DS3231_DateTime *dt) {
+  CTL_STATUS_t s;
+  uint8_t cmd[1] = { 0 };
+  uint8_t reply[7] = { 0 };
+
+  if (dt == NULL) {
+    return -1;
+  }
+
+  s = ctl_i2c_write_read(ds3231_i2c_bus, DS3231_ADDRESS,
+                         cmd, sizeof(cmd),
+                         reply, sizeof(reply));
+  if (s != 7+1)
+  {
+    return -1;
+  }
+
+  dt->seconds = bcd2bin(reply[0] & 0x7F);
+  dt->minutes = bcd2bin(reply[1]);
+  dt->hours = bcd2bin(reply[2]);
+  dt->day = bcd2bin(reply[4]);
+  dt->month = bcd2bin(reply[5]);
+  dt->year = bcd2bin(reply[6]) + 2000;
+  
+  return 0;
+}
+
+int RTC_DS3231_adjust(const struct DS3231_DateTime *dt) {
+  uint8_t cmd[8];
+  uint8_t reply[1];
+  CTL_STATUS_t s;
+
+  cmd[0] = 0;
+  cmd[1] = bin2bcd(dt->seconds);
+  cmd[2] = bin2bcd(dt->minutes);
+  cmd[3] = bin2bcd(dt->hours);
+  cmd[4] = bin2bcd(0);
+  cmd[5] = bin2bcd(dt->day);
+  cmd[6] = bin2bcd(dt->month);
+  cmd[7] = bin2bcd(dt->year - 2000);
+
+  s = ctl_i2c_write(ds3231_i2c_bus, DS3231_ADDRESS, cmd, sizeof(cmd));
+  if (s != sizeof(cmd)) {
+    return -1;
+  }
+
+  cmd[0] = DS3231_STATUSREG;
+  s = ctl_i2c_write_read(ds3231_i2c_bus, DS3231_ADDRESS, cmd, 1, reply, 1);
+  if (s != 2) {
+    return -2;
+  }
+  cmd[1] = reply[0] & (~0x80); // flip OSF bit
+  s = ctl_i2c_write(ds3231_i2c_bus, DS3231_ADDRESS, cmd, 2);
+  if (s != 2) {
+    return -3;
+  }
+
+  return 0;
+}
\ No newline at end of file
diff --git a/ds3231.h b/ds3231.h
new file mode 100644
--- /dev/null
+++ b/ds3231.h
@@ -0,0 +1,22 @@
+// Code originally by JeeLabs http://news.jeelabs.org/code/
+// Released to the public domain! Enjoy!
+
+#ifndef DS3231_H
+#define DS3231_H
+
+#include "ctl_i2c.h"
+
+struct DS3231_DateTime {
+  uint16_t year;
+  uint8_t month;
+  uint8_t day;
+  uint8_t hours;
+  uint8_t minutes;
+  uint8_t seconds;
+};
+
+int RTC_DS3231_init(CTL_I2C_BUS_t *i2c);
+int RTC_DS3231_now(struct DS3231_DateTime *dt);
+int RTC_DS3231_adjust(const struct DS3231_DateTime *dt);
+
+#endif /* DS3231_H */
\ No newline at end of file