MicroC PRO software is used
to make a program for microcontroller to control selected output. By using this
software we can create a program that can control several functions. For
example to control motor. The motor speed or angle of the motor can be control using
program. MicroC PRO have its own library contain an example of basic program
that can be use directly such as program for motor, LED display, LCD display,
temperature sensor and keypad.
For our project digital pH
meter, we need to make two programs. The first program is for analogue to
digital program. This program is important because to allow the LCD display can
display the pH value in digital form. LCD display can only read digital value.
What microcontroller do is,
it read the analogue output voltage or signal from pH meter circuit then
convert the value into digital before it can be display on LCD display. In
microcontroller pin, to convert analogue signal to digital signal, port A is
use because port A is for analogue input only.
The second program is LCD
display program. This program is made to display the pH value in digital and
also to display the temperature value in digital.
Figure
3.3.1 program for PIC controller
Figure above show the
overall program for our project. The program included analogue to digital
converter program and LCD display program.
PIC microcontroller is the
brain of our system in this project. PIC microcontroller has many advantages
especially to design the process itself. By using the MikroC PRO for PIC
software, we can simulate the circuit diagram on proteus before making the
actual hardware. Source code is easy to program which variety instructions that
we can programmed. There are many PIC type such as 16F84X, 16F877X, 18F8XX and
many more. In our case, we use PIC16F877A to create the program.
To create the source code
program, we need to insert the command, because, for our program have their own
command to let one system can be function. In this project, we use some of
command to displaying the value of pH and temperature such as the LCD library
command and the ADC library. For the display the items, we use LCD library that
we call them from the MikroC PRO for PIC for make communication with LCD (with
HD44780 compliant controllers). Through the 8-bit interface. An example of LCD
connections is given on the schematic from the pH meter circuit.
Figure
3.3.2 program code for LCD display
From the figure above, we
insert the LCD pin out setting and the LCD pin direction for 8-bit to enable
the value is function correctly. We use the port C and port D to enable the
connection that can be read and have a communication between PIC and the
display.
Figure
3.3.3 program code for LCD
From the figure above, we
create the lcd_init command to initializes LCD module. Then, we create the
Lcd_Out to prints text on LCD starting from specified position. Both string
variables and literals can be passed as a text. After that, we add the command Lcd_Out_Cp
to prints text on LCD at current cursor position. Both string variables and
literals can be passed as a text. We go to add the Lcd_Chr command to prints
character on LCD at specific position. Both variables and literals can be
passed as a character. Then, we add Lcd_Chr_Cp to prints character on LCD at
current cursor position. Both variables and literals can be passed as a
character. Lastly we put the Lcd_Cmd to sends command to the LCD and completing
the LCD program source code.
Figure
3.3.4 program code for ADC
From above figure is shown
the main program, we use an ADC (Analog to Digital Converter) module library.
Because the ADC is an electronic circuit that converts continuous signals to
discrete digital numbers to target the goals of this project as Digital pH
Meter as well. There are 3 main of command that must be used in creating the
program. That is ADC_Init command, this routine initializes PIC’s internal ADC
module to work with RC clock. Clock determines the time period necessary for
performing AD conversion. After that we use the ADC_Get_Sample, the function is
acquires analog value from the specified channel.
Parameter channel represents
the channel from which the analog value is to be acquired data. Lastly we add
the ADC_Read in this command, because this command initializes PIC’s internal
ADC module to work with RC clock. Clock determines the time period necessary
for performing AD conversion. The program of ADC command is to display the
analog signal from the circuit of pH meter convert to the digital signal that
can be display to the LCD display for the value of pH and also the value of
temperature. We use the ADC_float cause of to create the character with the
size of 15. Because we also want the output on the LCD can be read at the
decimal point. For read the value of pH, we dividing the result with 20.45, and
store the pH value before it can be display on the output display. For read the
value of temperature, we multiple the result with 0.48828 to display the
temperature result on LCD display.
Figure 3.3.6 program for display pH and Temperature
By referring the picture
above, we are use command Lcd_Out to display the value. We put the pH value at
the output by using the line 1 of text while we put the temperature value at
the output by using the line 2 of text.
