Latest revision as of 19:23, 13 June 2017

In this tutorial we are going to discuss the port configuration of PIC controllers. In this tutorial we will be using PIC16F877A as reference, same will be applicable for other PIC series controllers.
At the end of this tutorial you will be familiar with the PIC GPIO's and the associated registers for configuring and accessing the GPIO's.

GPIO Registers

The basic and important feature of any controllers is the number of gpio's available for connecting the peripherals. PIC16F877A has 33-gpio's grouped into five ports namely PORTA-PORTE as shown in the below table.

PORT	Direction Register	Number of Pins	Alternative Function
PORTA	TRISA	6 (PA0-PA5)	ADC
PORTB	TRISB	8 (PB0-PB7)	Interrupts
PORTC	TRISC	8 (PC0-PC7)	UART,I2C,PWM
PORTD	TRISD	8 (PD0-PD7)	Parallel Slave Port
PORTE	TRISE	3 (PE0-PB2)	ADC

As shown in the above table many I/O pins have 2-3 functions. If a pin is used for other function then it may not be used as a gpio.

Though the gpio pins are grouped into 8-bit ports they can still be configured and accessed individually.
Each Port is associated with 2 registers for direction configuration(Input/Output) and for Read/Write.

Register	Description
TRISx	Used to configure the respective PORT as output/input
PORTx	Used to Read/Write the data from/to the Port pins

note: Here 'x' could be A,B,C,D,E so on depending on the number of ports supported by the controller.

TRISx:TRI-State Register/ Data Direction Register
Before reading or writing the data from the ports, their direction needs to be set. Unless the PORT is configured as output, the data from the registers will not go to controller pins.

This register is used to configure the PORT pins as Input or Output. Writing 1's to TRISx will make the corresponding PORTx pins as Input. Similarly writing 0's to TRISx will make the corresponding PORTx pins as Output.

TRISB = 0xff;  // Configure PORTB as Input.
 
TRISC = 0x00; // Configure PORTC as Output.
 
TRISD = 0x0F; // Configure lower nibble of PORTD as Input and higher nibble as Output
 
TRISD = (1<<0) | (1<<3) | (1<<6); // Configure PD0,PD3,PD6 as Input and others as Output

PORTx:
This register is used to read/write the data from/to port pins. Writing 1's to PORTx will make the corresponding PORTx pins as HIGH. Similarly writing 0's to PORTx will make the corresponding PORTx pins as LOW.
Before reading/writing the data, the port pins should be configured as InputOutput.

PORTB = 0xff;  // Make all PORTB pins HIGH.
 
PORTC = 0x00;  // Make all PORTC pins LOW..
 
PORTD = 0x0F;  // Make lower nibble of PORTD as HIGH and higher nibble as LOW 
 
PORTD = (1<<PD0) | (1<<PD3) | (1<<PD6); // Make PD0,PD3,PD6 HIGH,
 
 
TRISB = 0x00;  // Configure PORTB as Output
TRISD = 0xff;  // Configure PORTD as Input
PORTD = PORTB; // Read the data from PORTB and send it to PORTD.

Led Blinking Example

After knowing how to configure the GPIO ports, its time to write a simple program to blink the Leds.

Configure the PORTS as outputs using TRIS registers.
Turn ON all the LEDs and wait for some time.
Turn OFF all the LEDs and wait for some time.

Led and Switches

Downloads

Download the complete project folder from the below link:
Hardware design Files and Code Library

Have a opinion, suggestion , question or feedback about the article let it out here!

@@ Line 1: / Line 1: @@
 [[Category:PIC Tutorials]]
+In this tutorial we are going to discuss the port configuration of PIC controllers. In this tutorial we will be using PIC16F877A as reference, same will be applicable for other PIC series controllers.<br>
-In this tutorial we are going to discuss the port configuration of AVR/Atmel controllers or in general Atmega family. In this tutorial we will be using Atmega32 as reference, same will be applicable to other Atmega series controllers.
+At the end of this tutorial you will be familiar with the PIC GPIO's and the associated registers for configuring and accessing the GPIO's.
+<br><br>
-At the end of this tutorial you will be familiar with the Atmega GPIO's and the associated registers for configuring and accessing the GPIO's.<br>
 =GPIO Registers=
-The basic and important feature of any controllers is the number of gpio's available for connecting the peripherals. Atmega32 has 32-gpio's grouped into four 8-bit ports namely PORTA-PORTD as shown in the below image.
+The basic and important feature of any controllers is the number of gpio's available for connecting the peripherals. PIC16F877A has 33-gpio's grouped into five ports namely PORTA-PORTE as shown in the below table.
+{| class="table table-striped table-hover table-condensed table-bordered"
+|-class="info"
-As shown in the above image many I/O pins have 2-3 functions. If a pin is used for other function then it may not be used as a gpio.
+|PORT|| Direction Register || Number of Pins || Alternative Function
+|-
+|PORTA|| TRISA || 6 (PA0-PA5) || ADC
+|-
+|PORTB|| TRISB || 8 (PB0-PB7) || Interrupts
+|-
+|PORTC|| TRISC || 8 (PC0-PC7) || UART,I2C,PWM
+|-
+|PORTD|| TRISD || 8 (PD0-PD7) || Parallel Slave Port
+|-
+|PORTE|| TRISE || 3 (PE0-PB2) || ADC
+|}
+As shown in the above table many I/O pins have 2-3 functions. If a pin is used for other function then it may not be used as a gpio.<br>
 Though the gpio pins are grouped into 8-bit ports they can still be configured and accessed individually.
-<br>Each Port is associated with 3 registers for direction configuration(Input/Output), read and write operation.
+<br>Each Port is associated with 2 registers for direction configuration(Input/Output) and for Read/Write.
+[[FILE:Pic16f877a_register_configuraion.png]]
 {| class="table table-striped table-hover table-condensed table-bordered"
 |-class="info"
 |Register||   Description
 |-
-|DDRx|| Used to configure the respective PORT as output/input
+|TRISx|| Used to configure the respective PORT as output/input
 |-
-|PORTx|| Used to write the data to the Port pins
+|PORTx|| Used to Read/Write the data from/to the Port pins
-|-
+|}
-|PINx|| Used to Read the data from the port pins
+note: Here 'x' could be A,B,C,D,E so on depending on the number of ports supported by the controller.
-|}note: Here 'x' could be A,B,C,D so on depending on the number of ports supported by the controller.
+<br><br>
-<b>DDRx:</b> Data Direction Register<br>
+<b>TRISx:</b>TRI-State Register/ Data Direction Register<br>
 Before reading or writing the data from the ports, their direction needs to be set. Unless the PORT is configured as output, the data from the registers will not go to controller pins.
-This register is used to configure the PORT pins as Input or Output. Writing 1's to DDRx will make the corresponding PORTx pins as output. Similarly writing 0's to DDRx will make the corresponding PORTx pins as Input.
+This register is used to configure the PORT pins as Input or Output. Writing 1's to TRISx will make the corresponding PORTx pins as Input. Similarly writing 0's to TRISx will make the corresponding PORTx pins as Output.
 <syntaxhighlight>
-DDRB = 0xff;  // Configure PORTB as Output.
+TRISB = 0xff;  // Configure PORTB as Input.
-DDRC = 0x00; // Configure PORTC as Input.
+TRISC = 0x00; // Configure PORTC as Output.
-DDRD = 0x0F; // Configure lower nibble of PORTD as Output and higher nibble as Input
+TRISD = 0x0F; // Configure lower nibble of PORTD as Input and higher nibble as Output
-DDRD = (1<<PD0) | (1<PD3) | (1<<PD6); // Configure PD0,PD3,PD6 as Output and others as Input
+TRISD = (1<<0) | (1<<3) | (1<<6); // Configure PD0,PD3,PD6 as Input and others as Output
 </syntaxhighlight>
+<br><br>
 <b>PORTx:</b><br>
-This register is used to send the data to port pins. Writing 1's to PORTx will make the corresponding PORTx pins as HIGH. Similarly writing 0's to PORTx will make the corresponding PORTx pins as LOW.
+This register is used to read/write the data from/to port pins. Writing 1's to PORTx will make the corresponding PORTx pins as HIGH. Similarly writing 0's to PORTx will make the corresponding PORTx pins as LOW.<br>
+<b>Before reading/writing the data, the port pins should be configured as InputOutput</b>.
 <syntaxhighlight>
 PORTB = 0xff;  // Make all PORTB pins HIGH.
-PORTC = 0x00; // Make all PORTC pins LOW..
+PORTC = 0x00;  // Make all PORTC pins LOW..
-PORTD = 0x0F; // Make lower nibble of PORTD as HIGH and higher nibble as LOW
+PORTD = 0x0F;  // Make lower nibble of PORTD as HIGH and higher nibble as LOW
-PORTD = (1<<PD0) | (1<PD3) | (1<<PD6); // Make PD0,PD3,PD6 HIGH,
+PORTD = (1<<PD0) | (1<<PD3) | (1<<PD6); // Make PD0,PD3,PD6 HIGH,
-</syntaxhighlight>
-<b>PINx:</b>PORT Input Register<br>
-This register is used to read the data from the port pins. Before reading the data from the port pins,  the ports needs to be configured as Inputs.
-<syntaxhighlight>
-DDRB  = 0x00; // Configure the PORTB as Input.
-value = PINB;  // Read the data from PORTB.
-DDRB = 0x00; // Configure PORTB as Input
+TRISB = 0x00;  // Configure PORTB as Output
-DDRD = 0xff;  // Configure PORTD as Output
+TRISD = 0xff;  // Configure PORTD as Input
-PORTD = PINB; // Read the data from PORTB and send it to PORTD.
+PORTD = PORTB; // Read the data from PORTB and send it to PORTD.
-</syntaxhighlight>
-<b>Enabling Internal Pull Up Resistors:</b><br>
-Making the DDRx bits to 0 will configure the PORTx as Input. Now the corresponding bits in PORTx register can be used to enable/disable pull-up resistors associated with that pin.To enable pull-up resistor, set bit in PORTx to 1, and to disable set it to 0.
-<syntaxhighlight>
-DDRB  = 0x00;  // Configure the PORTB as Input.
-PORTB = 0xFF;  // Enable the internal Pull Up resistor of PORTB.
-DDRD = 0xff;  // Configure PORTD as Output
-PORTD = PINB; // Read the data from PORTB and send it to PORTD.
 </syntaxhighlight>
+<br><br>
 =Led Blinking Example=
 After knowing how to configure the GPIO ports, its time to write a simple program to blink the Leds.
-<br>Below points needs to be considered for this example.
+#Configure the PORTS as outputs using TRIS registers.
-* Include the io.h file as it has the definitions for all the PORT registers.
+#Turn ON all the LEDs and wait for some time.
-* Include delay.h file to use the delay functions.
+#Turn OFF all the LEDs and wait for some time.
-* Configure the PORT as Output before writing any data to PORT pins.
 <html>
-<script src="https://gist.github.com/SaheblalBagwan/a671ac5b9c722f350a9d.js"></script>
+<script src="https://gist.github.com/sharanago/6561921de354fc92f5254845dcc16063.js"></script>
 </html>
-==Led Blinking Wiring Diagram==
+<br><br>
-[[File:Blink bb.png|x480px|center]]
 =Led and Switches=
 <html>
-<script src="https://gist.github.com/SaheblalBagwan/310b1582e0bec2ad28ad.js"></script>
+<script src="https://gist.github.com/SaheblalBagwan/614103c3fa59fa99864bc71a03b99302.js"></script>
 </html>
-==LEDs and Switches Wiring diagram==
-<html><img src ="https://www.exploreembedded.com/blog/wp-content/uploads/img-collections/fritzing-tutorials_de69ccc2/switch_bb.png" width="670 px"></html>
+=Downloads=
+Download the complete project folder from the below link:<br>
+[https://github.com/ExploreEmbedded/Pic16f877a_ExploreUltraPicDevKit/archive/master.zip Hardware design Files and Code Library]
 Have a opinion, suggestion , question or feedback about the article let it out here!
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Difference between revisions of "PIC I/O Register Configuration"

Latest revision as of 19:23, 13 June 2017

Contents

GPIO Registers

Led Blinking Example

Led and Switches

Downloads