Learn To Write Code For 8051, Arduino, AVR, dsPIC, PIC, STM32 ARM Microcontroller, etc.
Coding Embedded Controller With C/C++.
Printed Circuit Board (PCB) Project For Electronics Hobbyists.
Using a prototype board for micro-controller firmware testing could save time and safer. Putting an on-board device programmer with prototype board could be more satisfy for electronic hobbyists.
I have some PIC18 and PIC16 series of micro-controllers left from previous projects. I don't know what to do with them anymore. So I put them on single board to PIC program testing next time I need them without checking their pin diagram, and wiring them on bread board.
PCB Front View
PCB Back View
I designed a PCB with a
PICKit2 device programmer (with AVR ISP header)
+5VDC and +3.3VDC low drop out power supply
RS-232 to TTL logic converter
I2C DS1307 RTC and 24LC08 EEPROM
4-bit LCD (HD4478)
3-digit 056'common cathode multiplexing display
One passive buzzer with transistor driver (using CCP1 PWM output pin of PIC16F876A)
8-LED that connects to PORTC of PIC16F876A
A 4x4 keypad matrix that connects to PORTB of PIC16F876A
Three analog inputs (one LM35 and two potentiometers) that connect to RA0...RA1 of PIC16F876A.
A 28-pin IC socket for 28-pin PIC devices
A 20-pin IC socket for 20-pin PIC devices
A 18-pin IC socket for 18-pin PIC devices
A 14-pin IC socket for 14-pin PIC devices
And a 8-pin IC socket for 8-pin PIC devices
This board seem to be a large PCB with two copper layer near a size of an A4 paper that I'm not yet fabricate it. It need a PCB fabrication service.
Schematic
I use Protues VSM Release 8.16 SP3 to design draw its circuit diagram. Some components are not in its original libraries. So I find and download some devices symbol, footprints and 3D objects from snapeda website. I separate its schematic into A4 sheets.
Sheet #1
Sheet #2
Sheet #3
Sheet #4
Sheet #5
This board could fit,
28-pin PIC microcontrollers: PIC16F876A, PIC16F886, etc.
20-pin PIC microcontrollers: PIC16F1459(USB), PIC16F690, etc.
18-pin PIC microcontrollers: PIC16F1827, PIC16F84A, PIC16F818, etc.
14-pin PIC microcontrollers: PIC16F630, PIC16F676, etc.
8-pin PIC microcontrollers: PIC12F629, PIC12F675, PIC12F683, etc.
These are some mid-range PIC micro-controllers I have at my own workshop.
Printed Circuit Board (PCB)
This board size is 8.02x6.30 inches that could be a little bit expensive to order from any professional PCB fabrication service. But if we need to use it with classmate or friend the share cost is cheaper.
Top Copper non-mirror
Bottom Copper
Top Silk
I preview this PCB on an online Gerber viewer software.
I have been using PCBWay for many years now. PCBWay fabricate PCBs at low cost,
fast processing time for only 24 hours, and fast delivery time using
any carrier options. This double side 10cmx10cm can be fabricate at only
5USD for 5 to 10pcs by PCBWay. It's a standard PCB with silk screen and
solder mask.
An electronics digital clock usually equipped with a Real Time Clock (RTC) IC – for example DS3231 RTC. However we can build a non-complex one’s using internal timer of a microcontroller. This feature doesn’t have time keeping as RTC chip. It lost all its previous timing when it’s powered off.
A commercial sample of DS3231 RTC module from Ali Express
Digital Clock made from Timer0
Timer0 module creates a precise timing when it’s running in timer mode. Timing tick period is configurable by user. A a simple programming example we start with showing timing data on a multiplexing display.
Hardware Preparation
Main controller powered by PIC16F818 microcontroller. It’s suitable for this simple project. Display is assumed to be a dedicated digital clock display in multiplexing type. It’s common anode type as there’s no other option.
Schematic diagram
We don’t use external reset on RA5 pin. Higher nibble of Port A is reserved for digital inputs. These four inputs are minute and second adjustment. Controller clocks from its internal 8MHz oscillator.
Program Preparation
Blueprint of this digital clock project is Timer0 interrupt. Timer0 clock source is internal microcontroller clock with 1:2 prescaler. Timer0 interrupt creates timing tick of 100us. Each time the interrupt occurs Timer0 register is preloaded with 100 to get this timing interval.
Display
Multiplexing display is activated for every 5ms for each digit. A counting register schedule this task. It runs from 0 to 20ms before it rolls back to 0.
Buttons
Four input buttons are,
Increasing minute on RA4
Decreasing minute on RA5
Increasing second on RA6
Increasing second on RA7
Each button pressing will be accept by controller after 200ms. This 200ms timer tick create by buttonTime counting variable. Whenever any button is pressed time adjustment is made, and this time counting variable is reset to 0.
Timer0 Interrupt
ISR of PIC16F818 keeps track of Timer0 overflow interrupt. Each time interrupt occurs Timer0 Register (TMR0) preload with value of 100 to gain a 100us timer tick.
PIC16F818 C configuration settings store in “pic16f818Config.h” file.
// PIC16F818 Configuration Bit Settings // CONFIG #pragma config FOSC = INTOSCIO // Oscillator Selection bits (INTRC oscillator; port I/O function on both RA6/OSC2/CLKO pin and RA7/OSC1/CLKI pin) #pragma config WDTE = OFF // Watchdog Timer Enable bit (WDT disabled) #pragma config PWRTE = OFF // Power-up Timer Enable bit (PWRT disabled) #pragma config MCLRE = OFF // RA5/MCLR/VPP Pin Function Select bit (RA5/MCLR/VPP pin function is MCLR) #pragma config BOREN = ON // Brown-out Reset Enable bit (BOR enabled) #pragma config LVP = OFF // Low-Voltage Programming Enable bit (RB3/PGM pin has digital I/O function, HV on MCLR must be used for programming) #pragma config CPD = OFF // Data EE Memory Code Protection bit (Code protection off) #pragma config WRT = OFF // Flash Program Memory Write Enable bits (Write protection off) #pragma config CCPMX = RB2 // CCP1 Pin Selection bit (CCP1 function on RB2) #pragma config CP = OFF // Flash Program Memory Code Protection bit (Code protection off)
Click here to download source file. Its statistic shown below.
Analog-to-Digital Converter (ADC) operates with analog signal input to microcontroller. Input signal from any device is converted to analog voltage before it’s fed to analog input pin.
Typical reference voltage of ADC is 5V. Maximum direct input voltage to analog input channel must not exceed +5V. For a 10-bit resolution ADC the step voltage is 0.048V.
In this example the controller is programmed to read and show input voltage to ADC input channel 0 – AN0 of PIC16F818. The result will show on a single common anode 7-Segments display.
Programming in MPLABX XC8
There are some additional codes over previous post that convert ADC result to analog voltage, and displaying. A display is one inch in digit size.
One inch red common anode seven-segments display
Circuit Design
System runs without external crystal oscillator as it comes with internal oscillator with maximum 8MHz frequency.
Schematic Design
AN0 reads input voltage while Port B display the result. Input voltage is varied due to the adjustment of RV1 POT.
Programming
Main program loop keeps track of ADC reading and result updating. Most of source code here is often seen in some previous posts relate to PIC16F818 ADC programming in MPLABX XC8.
/* * PIC16F818 Analog Voltage Reading */ #include <xc.h> // PIC16F818 Configuration Bit Settings #pragma config FOSC = INTOSCIO // Oscillator Selection bits (INTRC oscillator; port I/O function on both RA6/OSC2/CLKO pin and RA7/OSC1/CLKI pin) #pragma config WDTE = OFF // Watchdog Timer Enable bit (WDT disabled) #pragma config PWRTE = OFF // Power-up Timer Enable bit (PWRT disabled) #pragma config MCLRE = ON // RA5/MCLR/VPP Pin Function Select bit (RA5/MCLR/VPP pin function is MCLR) #pragma config BOREN = ON // Brown-out Reset Enable bit (BOR enabled) #pragma config LVP = OFF // Low-Voltage Programming Enable bit (RB3/PGM pin has digital I/O function, HV on MCLR must be used for programming) #pragma config CPD = OFF // Data EE Memory Code Protection bit (Code protection off) #pragma config WRT = OFF // Flash Program Memory Write Enable bits (Write protection off) #pragma config CCPMX = RB2 // CCP1 Pin Selection bit (CCP1 function on RB2) #pragma config CP = OFF // Flash Program Memory Code Protection bit (Code protection off) void readVoltage(void){ /*Seven-Segment output data*/ char displayAnode[10]={0xC0,0xF9,0xA4,0xB0,0x99,0x92,0x82,0xF8,0x80,0x90}; /*Start the conversion*/ ADCON0bits.GO_nDONE=1; /*When GO_nDONE is clear A/D conversion is completed*/ while(GO_nDONE); /*Wait for some microseconds*/ for(int i=0;i<1000;i++); /*Make a 10-bit A/D converter result*/ int _L=ADRESL; int _H=ADRESH; unsigned int adcResult=(_H<<8)+_L; /*convert to voltage with +0.1V offset*/ adcResult=(float)adcResult*5.1/1024; /*Show voltage reading*/ PORTB=displayAnode[adcResult]; } void main(void){ /*Select 8MHz internal oscillator*/ OSCCONbits.IRCF=0x07; /*Clear Port A*/ PORTA=0x00; /*Clear Port B*/ PORTB=0x00; /*RA0 analog input*/ TRISA=0x01; /*Port B digital output*/ TRISB=0x00; /*Select internal RC oscillator of A/D converter*/ ADCON0bits.ADCS=0x01; /*Select analog channel 0 - AN0*/ ADCON0bits.CHS=0x00; /*RA0-AN0 analog input, AVDD and AVSS voltage references*/ ADCON1bits.PCFG=14; /*Result is right justified*/ ADCON1bits.ADFM=1; /*Turn on A/D converter module*/ ADCON0bits.ADON=1; /*Main Program Loop*/ while(1){ readVoltage(); } }
Click hereto download zip file of this working example.
In previous article we have shown about A/D converter module of PIC16F818, and its programming example in MPLABX XC8. We are going to make more programming example using this analog input peripheral module inside this PIC device.
LED bar-graph is a popular LED display that show analog level status of any quantity – analog voltage, water level, and VU indicator. For example an bar-graph display indicating level of remaining energy of a smart phone power bank.
A simulation sample of this example
LED Bar-graph Programming Example With A/D Converter
PIC microcontroller will be programmed to display bar-graph output with nine value – from null to its maximum display on. Analog input connects to RA0/AN0 while its analog representation will be displayed on Port B.
Circuit Design
Resistor network and LED bar-graph are more convenience in this programming example. They are packed in one package making an ease of circuit wiring on breadboard.
Circuit Diagram
This controller operates from its 8MHz internal oscillator due to economics issue and ease of design. An external reset on MCLR is needed as an aid of controller being stuck.
XC8 Programmingfor A/D Converter
Most of programming source code is similar to previous example. It excepts an additional lines of code that process bar-graph LED display. C program convert A/D converter 8-bit result pair to its 10-bit resolution.
An additional step converts this 1024 decimal value to 9 value range to fit 8-LED bar-graph display.
/* * PIC16F818 A/D Converter Example 2 * A/D reading bargraph display */ #include <xc.h> #include "pic16f818_config.h" /*Set oscillator to 8MHz*/ #define _XTAL_FREQ 8000000 void main(void){ /*LED Bar Graph Representation*/ char barGraph[9]={0,0b00000001,0b00000011,0b00000111,0b00001111, 0b00011111,0b00111111,0b01111111,0b11111111}; /*Select 8MHz internal oscillator*/ OSCCONbits.IRCF=0x07; /*Clear Port A*/ PORTA=0x00; /*Clear Port B*/ PORTB=0x00; /*RA0 analog input*/ TRISA=0x01; /*Port B digital output*/ TRISB=0x00; /*Select internal RC oscillator of A/D converter*/ ADCON0bits.ADCS=0x01; /*Select analog channel 0 - AN0*/ ADCON0bits.CHS=0x00; /*RA0-AN0 analog input, AVDD and AVSS voltage references*/ ADCON1bits.PCFG=14; /*Result is right justified*/ ADCON1bits.ADFM=1; /*Turn on A/D converter module*/ ADCON0bits.ADON=1; /*Main Program Loop*/ while(1){ /*Start the conversion*/ ADCON0bits.GO_nDONE=1; /*When GO_nDONE is clear A/D conversion is completed*/ while(GO_nDONE); /*Wait for some microseconds*/ for(int i=0;i<1000;i++); /*Make a 10-bit A/D converter result*/ int _L=ADRESL; int _H=ADRESH; unsigned int barValue=(_H<<8)+_L; /*Convert A/D result to 9 values*/ barValue=(float)barValue*9.0/1024; /*Display bargraph on Port B*/ PORTB = barGraph[barValue]; } }
Configuration bits keep in C header file “pic16f818_config.h” in the same project directory.
// PIC16F818 Configuration Bit Settings // CONFIG #pragma config FOSC = INTOSCIO // Oscillator Selection bits (INTRC oscillator; port I/O function on both RA6/OSC2/CLKO pin and RA7/OSC1/CLKI pin) #pragma config WDTE = OFF // Watchdog Timer Enable bit (WDT disabled) #pragma config PWRTE = OFF // Power-up Timer Enable bit (PWRT disabled) #pragma config MCLRE = ON // RA5/MCLR/VPP Pin Function Select bit (RA5/MCLR/VPP pin function is MCLR) #pragma config BOREN = ON // Brown-out Reset Enable bit (BOR enabled) #pragma config LVP = OFF // Low-Voltage Programming Enable bit (RB3/PGM pin has digital I/O function, HV on MCLR must be used for programming) #pragma config CPD = OFF // Data EE Memory Code Protection bit (Code protection off) #pragma config WRT = OFF // Flash Program Memory Write Enable bits (Write protection off) #pragma config CCPMX = RB2 // CCP1 Pin Selection bit (CCP1 function on RB2) #pragma config CP = OFF // Flash Program Memory Code Protection bit (Code protection off)
User can write these configuration codes within C main program.
Program Testing
This embedded controller program was primarily tested in software simulator.
Microcontroller simulation in Proteus 8
Click here to get zip file of this working example.
