Pi4j Pin Reference Model 3B
http://pi4j.com/pins/model-3b-rev1.html

Compile Java
javac -classpath ./RXTXcomm.jar SerialTest.java
Run
java -Djava.library.path=/usr/lib/jni  -cp ./RXTXcomm.jar: SerialTest

https://www.youtube.com/watch?v=cVdSc8VYVBM

CLOCK - DS3231
1. VCC      1. 3.3v
2. Data     3. GPIO 8
3. Clock    5. GPIO 9
4. NC       7. GPIO 7
5. Ground   9. Ground

apt-get install wiringpi

HX711
1. VCC      4.  5v
2. SCK      8.  GPIO15
3. DT       10. GPIO16 
4. Ground   6.  Ground


HD44780 MAPPING
1.  Ground   >   25. Ground
2.  VCC      >   2.  5v
3.  Contrast >   30. Ground
4.  RS       >   36. GPIO > PI4J 25
5.  R/W      >   34. Ground
6.  Enable   >   38. GPIO > PI4J 24
7.  Not Used
8.  Not Used
9.  Not Used
10. Not Used
11. LCD D4   >   31. GPIO > PI4J 27
12. LCD D5   >   33. GPIO > PI4J 28
13. LCD D6   >   35. GPIO > PI4J 29
14. LCD D7   >   37. GPIO > PI4J 26
15. LED+     >   17. 3.3v
16. LED-     >   39. Ground 


CALIBRATION:
Minimum Weight
Maximum Weight
Scale Interval: d value: smallest division shown on the scale display.
Verification Interval: e value: is the verification scale division. It represents the stated accuracy of a scale when the scale display has extra units added in order to expand the resolution. The verification scale division (e) may be larger than the displayed scale division (d) for some devices.