Merge pull request #98 from mores/mcp7941x

Add RealTimeClock - Mcp7941xDriver.

Author: stefanhaustein

src/main/java/com/pi4j/drivers/sensor/geospatial/mcp7941x/Mcp7941xDriver.java

@@ -0,0 +1,72 @@
+package com.pi4j.drivers.sensor.geospatial.mcp7941x;
+
+import java.time.LocalDateTime;
+
+import com.pi4j.io.i2c.I2C;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Mcp7941xDriver {
+    private static Logger log = LoggerFactory.getLogger(Mcp7941xDriver.class);
+
+    private static final int START_OSCILLATOR = 0x80;
+
+    private static final int SECONDS = 0x00;
+    private static final int MINUTES = 0x01;
+    private static final int HOURS = 0x02;
+    private static final int DAY_OF_WEEK = 0x03;
+    private static final int DAY = 0x04;
+    private static final int MONTH = 0x05;
+    private static final int YEAR = 0x06;
+
+    private final I2C i2c;
+
+    public Mcp7941xDriver(I2C i2c) {
+
+        this.i2c = i2c;
+    }
+
+    public LocalDateTime getDateTime() {
+
+        int year = bcdToDec(i2c.readRegister(YEAR)) + 2000;
+        int month = bcdToDec(i2c.readRegister(MONTH));
+        int day = bcdToDec(i2c.readRegister(DAY));
+
+        int hour = bcdToDec(i2c.readRegister(HOURS));
+        int minute = bcdToDec(i2c.readRegister(MINUTES));
+        int seconds = bcdToDec(i2c.readRegister(SECONDS) & 0x7F);
+
+        return LocalDateTime.of(year, month, day, hour, minute, seconds);
+    }
+
+    public void setDateTime(LocalDateTime localDateTime) {
+
+        log.trace("setting dateTime: " + localDateTime);
+
+        i2c.writeRegister(SECONDS, (byte) decToBcd(localDateTime.getSecond()) | START_OSCILLATOR);
+        i2c.writeRegister(MINUTES, (byte) decToBcd(localDateTime.getMinute()));
+        i2c.writeRegister(HOURS, (byte) decToBcd(localDateTime.getHour()));
+
+        i2c.writeRegister(DAY, (byte) decToBcd(localDateTime.getDayOfMonth()));
+        i2c.writeRegister(MONTH, (byte) decToBcd(localDateTime.getMonthValue()));
+        i2c.writeRegister(YEAR, (byte) decToBcd(localDateTime.getYear() - 2000));
+    }
+
+    // limited to 2 digits ( 0..99 )
+    private static int bcdToDec(int bcd) {
+        return ((bcd >> 4) * 10) + (bcd & 0x0F);
+    }
+
+    // limited to 2 digits ( 0..99 )
+    private static int decToBcd(int val) {
+
+        if (val < 0) {
+            throw new IllegalArgumentException();
+        }
+
+        int result = ((val / 10) << 4) | (val % 10);
+        log.trace("decToBcd in: {} out: {}", val, result);
+        return result;
+    }
+}