PIC16F887 ADC Simple DVM Example MikroC

In previous post, we demonstrate how to program ADC module of PIC16F887 using MikroC for PIC. However its result was just a binary representation of 10-bit ADC resolution. 

Typically, input voltage to ADC input channel ranges around its ADC reference voltage - about 5V. Thus input voltage of analog input is between 0 to 5V DC. In this programming example, controller read analog input voltage using its ADC module, and display the value of voltage on a multiplexing 7-Segments display.

Sample of this programming example

Analog input channel 0 (AN0) reads input voltage. C program configures, and converts analog input value to digital representation. Another block of code convert digital conversion result to readable voltage value in floating point format.

MikroC source code:

#define STEP_SIZE 0.0048
#define ONE_SECOND 30
#define RATE 10
#define DIGIT1 PORTA.RA6
#define DIGIT2 PORTA.RA7
 
unsigned ADC_Value;
float  Voltage;
char int_count,volt_count;
char LED[10]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F};
bit  ADC_RUN;
 
void interrupt() {
     if(INTCON.T0IF) {
        int_count++;
        if(int_count==ONE_SECOND)
        { int_count=0; ADC_RUN=1; }
        }
     INTCON.T0IF=0;
}
 
void PORT_SETUP() {
     PORTA=0x00;
     PORTB=0x00;
     TRISA=0x01;   // RA0 IS ANALOG IN PUT
     TRISB=0x00;   // PORTB is OUTPUT
     ANSEL=0x01;   // SELECT AN0
     ANSELH=0x00;   // OTHERS ARE DIGITAL IO
     OSCCON|=0x07;  // SELECT 8MHz INT RC
     }
 
void Timer0_Setup(){
     OPTION_REG.T0CS=0; // SELECT FOSC/4
     OPTION_REG.PSA=0;  // SELECT TIMER0 PRESCALER
     OPTION_REG|=0x07;  // SELECT 1:256 PRESCALER
     }
 
void interrupt_setup() {
     INTCON.GIE=1;
     INTCON.T0IE=1;
     INTCON.T0IF=0;
     }
 
void Read_Voltage () {
     if(ADC_RUN=1) {
        ADC_Value=ADC_Get_Sample(0);   // READ AN0
        delay_ms(10);
        Voltage=ADC_Value*STEP_SIZE;  // Convert to Decimal
      }
       ADC_RUN=0;
}
 
void SSD() {
     volt_count=Voltage*10;  // convert Voltage to integer
 
     PORTB=LED[Volt_count/10]|0x80;
     DIGIT1=1;
     delay_ms(RATE);
     PORTA=0x00;
 
     PORTB=LED[Volt_count%10];
     DIGIT2=1;
     delay_ms(RATE);
     PORTA=0x00;
}
 
void main() {
     ADC_Value=0;
     int_count=0;
     ADC_RUN=0;
     PORT_SETUP();
     ADC_Init();
     Timer0_Setup();
     Interrupt_Setup();
     while(1) {
     Read_Voltage();
     SSD();
     }
}

Multiplexed display is common cathode type, driven by an inverting buffer. Embedded controller operates from its 8MHz internal oscillator.

Schematic Diagram:

Schematic diagram

Click here to download this example.

PIC16F887 dual ADC reading example MikroC

In previous post, we show how to program ADC in MikroC. It was a single channel reading. We can read any channel as need by setting a number of ADC input, and selecting a specific channel before reading.

Simulation sample of this program

In this example, program is written to read one of two ADC channels. An additional digital switch used for selecting one of these two channel. Its ten-bit ADC result will display on PORTD and PORTC.

MikroC program:

#define SW PORTA.RA7
 
void PORT_Init() {
     PORTA=0x00;        // Clear PORTA
     PORTC=0x00;        // Clear PORTC
     PORTD=0x00;        // Clear PORTD
     PORTB=0x00;        // Clear PORTB
     PORTA=0x83;        // RA0-RA1-RA7 are INPUT
     ANSEL=0x03;        // RA0 IS ANALOG
     TRISC=0x00;        // PORTC AS OUTPUT
     TRISD=0x00;        // PORTD AS OUTPUT
     }
 
void Analog_Init() {
     ADCON0=0x80;       // Select Fosc/32 AND AN0
     ADCON1=0x80;       // Select Right Justified and VDD-VSS
     ADCON0.ADON=1;     // Enable ADC Module
     }
 
 
void Read_ADC() {
     delay_ms(10);
     if(SW==1)  ADCON0|=0x04;      // select AN1
     else       ADCON0&=0x83;      // select AN0
     ADCON0.GO=1;                  // start of conversion
     while(ADCON0.GO);             // waiting for Conversion's Complete
     PORTC=ADRESL;
     PORTD=ADRESH;
     }
 
void main() {
     PORT_Init();
     OSCCON|=0x70;     // Select Internal 8MHz OSC
     Analog_Init();
     while(1)   Read_ADC();
}

Click here to download this example.

Schematic diagram:

Schematic diagram

PIC16F887 operates at 8MHz from its internal oscillator.

PIC16F887 Analog-to-Digital Converter (ADC)

Introduction

Analog-to-Digital Converter (ADC) module of a microcontroller converter analog input voltage to digital value representation that microcontroller process with. There are many different types of ADC module inside microcontroller.

ADC module has some parameters:

1. Resolution : Define the amount of digital number of analog to digital conversion. It could be 8-bit, 10-bit, 12-bit, etc. Larger resolution gives the conversion result more accurate.
   
2. Voltage reference: It also effect Resolution. Lower voltage reference of ADC makes an accurate conversion result. It could be 2.5V, 3.3V, or 5V.
3.  Clock : It could be driven from microcontroller clock source, or its own internal clock. 
4. Number of Analog Input Channel : It  refers to the amount of input pins of ADC. It usually multiplexed with other digital I/O pins.
   

The figure below is ADC block diagram of PIC16F887.

Block diagram of PIC16F887 ADC Module

PIC16F887 has up to 14 analog input channels. They are multiplex within Port A and Port B.

Programming for ADC

ADC module inside PIC16F887 has some registers for programmer to work with. Programmer need to configure,

1. ADC clock
2. Analog channel inputs
3. Result arrangement
4. Channel selection
5. Start of conversion
6. Testing the result and reading the result
7. Interrupt control (optional)
   

 These registers are,

Registers relate to ADC of PIC16F887

Now let start a simple example of using ADC module. This program read analog input on RA0/AN0. Conversion result will display on Port C and Port D.

Schematic Diagram

 MikroC source code:

Click here to download zip file of this working example.