UPC EETAC Bachelor's Degree in Telecommunications Systems and in Network Engineering EEL

 

1-digit BCD counter with LCD (LAB10 design phase #2)

P11

FSM + interrupts + plan X + LCD

1. Specifications Planning Dev. & test Prototype  report

Add an LCD to the basic Counter_BCD_1digit from design phase #1. The new Counter_BCD_1digit_LCD will show static ASCII messages (design step #1) and dynamic numeric data (design step #2). 

Symbol

Fig 1. Symbol of the device to be designed.

 

Specifications 2. Planning Dev. & test Prototype  report

All planning is inherited from design phase #1 and no need to report it again. Let us focus simply on what changes and adaptation will imply interfacing the LCD.

A) Planning hardware

If we consider the CSD_PICstick board wiring, the simplest way to interface an LCD is to use PORTD, as represented in Fig. 1. The interface will be managed by high-level library functions. We will only write to the LCD, connecting RW = '0'. In this simple parallel interface we use six port D pins RD(5..0). A 10 kΩ potentiometer will adjust the LCD contrast to make the characters clear and visible.

Hardware circuit
LCD interface

Fig. 2. Connecting 6 microcontroller port pins for the LCD interface.

 

B) Planning software

For this design step #1 where only static messages will be represented on the LCD screen,  no new RAM variables are required.

Hardware-software modifications

Fig. 3. Hardware-software diagram highlighting small modifications for connecting the LCD. Basically, the var_LCD_flag to be set only when new information is printed. The LCD is handled by specific functions from the LCD library.

The state diagram is the same as it was in design phase #1 adding LCD instructions to print messages.

State_diagram modification

Fig. 4. State diagram indicating the ASCII messages in each state.

output_logic() generates an static ASCII message in each state. 

state_logic() is the same, only clearing the LCD flag once used.

init_system() includes LCD initialisation.

read_inputs() to capture CE signal the same.

write_outputs() is the same because writing to the LCD is carried out by the LCD library routines.

ISR() to handle CLK edge detections is the same.

 

Organise a MPLABX - XC8 IDE project targeting a PIC18F46K22 at location:

C:\CSD\P11\counter_BCD_1digit_LCD\(files)

 

Specifications Planning 3. Dev. & 4. test Prototype  report

A) Developing hardware

Parallel 6-wire interface. We will use the RD(5..0) through the expansion connector to interface the LCD. We need to find C libraries as it was proposed in P11. The reference and LCD libraries for this design are found here.

This is the "Counter_BCD_1digit_LCD.pdsprj" hardware circuit.

Proteus schematic

Fig. 8. Proteus schematic. 

 

B) Developing software

The XC8 compiler version is v3.0 or newer, C standard is C99. And these LCD library files "lcd.c", "lcd.h" has to be included in the project. The file "config.h" contains all the microcontroller configuration bits.

This "Counter_BCD_1digit_LCD.c " the software C source program.

Compiler options and source files

Fig. 9. Library files and compiler options. To disable some warnings you can add these additional XC8 Compiler options: -Xparser -Wno-implicit-int-conversion -Wno-implicit-int-float-conversion. MPLAB XC8 C Compiler Use's Guide for PIC MCU.

 

C) Step-by-step testing

Proteus schematic running the application

Fig. 10. Proteus schematic running and watching RAM variables. 

Alternative serial 2-wire I2C interface. Another alternative way to interface the LCD simplifying the connections to only two signal wires is to use the bus I2C adapter. This schematic can also be simulated in Proteus before prototyping because the chip PCF8574 model is available. To proceed with this idea, we need to find a C language high-level LCD library for the XC8. Ref1., ref2., ref3.

I2C interface
Adapter I2C LCD

Fig 4. Synchronous serial I2C interface.

 

Specifications Planning Dev. & Test 5. Prototype  Report

 

 

 

Specifications Planning Dev. & Test Prototype 6. Report

Follow this rubric for writing reports.