Serial Data Received from PC and Displayed on 16x2 Using USART of Pic16f877 Microcontroller

Here is a simple tutorial on how to receive serial data from PC(Personal Computer) Hyper-terminal and display it on 16×2 lcd using PIC16f877 microcontroller. Its not much difficult you just need to know how to use USART(Universal Synchronous-Asynchronous receiver transmitter) of PIC 16f877. Serial data is transmitted and received by PC using DB-9 OR DB-25 port of PC.

PIC16f877 Microcontroller
16×2 lcd
MAX232
PC with DB-9 or DB-25 Port
Potentiometer (For Setting LCD Contrast)
Crystal 20MHz
Connecting Wires & Power Supply

Microcontrollers works on TTL(Transistor Transistor Logic) wave form & standard PC(Personal Computers) works on RS-232 level wave form. Serial Data Transmitted by PC is in RS-232c level wave form. We have to convert this RS-232c wave form data in TTL form, to pass it to PIC16f877. The best way is to use MAX-232 ic. MAX-232 converts RS-232c level wave form data in TTL & TTL data in RS-232c level. Below is a simple Diagram of both the wave forms.

RS-232c to TTL and TTL to RS-232c conversion

Serial communication using Pic microcontroller – Circuit diagram

Port-B of PIC 16f877 is connected to data pins of 16×2 lcd. RS(Register-Select) Pin of lcd is connected to Port-D Pin#6. En(Enable) Pin of lcd is connected to Port-D Pin#7. RW(Read-Write) Pin is grounded Because we only want to write to lcd. You can also connect RW pin to Port-D Pin#5 Because Rw is also programmed in software burned in PIC 16f877.

USART of PIC 16f877 is present at Pin 25 & 26 of PIC 16f877 Microcontroller. USART Include Port-C Pin#6 & 7. RC6 can be used as TX(Transmission) and RC7 can be used as RX(Reception). Since we are receiving data from PC and then displaying it on 16×2 lcd so we are only concerned with RX(Reception) pin of USART. This RX pin is connected to Pin#12(R1OUT) of MAX-232. Pin#13(R1IN) of MAX-232 is connected to PIN#3 of DB-9 Port.

Both the tutorials above are very important for you, if you are new and didn’t use the stuff before in any project. I recommend you to go through them it will help you a lot in understanding the circuit diagram and working of both the things. Circuit diagram of the project is given below.

Serial Data Received from PC and displayed on 16x2 Lcd using Pic16f877A USART

Serial Data Received from PC and displayed on 16×2 Lcd using Pic16f877A USART

Pic microcontroller serial communication – Project code

Code is written in c language using MPLAB-ide and High Tech C compiler is used to compile the code. First High Tech C-compiler header file htc.h is imported in the project. Then Crystal frequency is defined which is 20MHz. RD7,RD6 & RD5 pins of Port-D are initialized as EN, RS & RW, Control pins for 16×2 lcd. lcdcmd() function is sending commands to lcd and control these commands. display() function is sending data to lcd, controls this data by controlling EN,RW & RS pins of lcd. lcdint() function is initializing our lcd and Microcontroller ports.

In the main function first TRISC7=1 is initializing RX pin as input. TXSTA(Transmit Status and Control Register) is initializing USART in Asyncronous Mode with High Speed Baud Rate. 0x04 is loaded in TXSTA.

TXSTA Register Bits—- Pic16f87X series

RCSTA(Receive status and control register) Register is used for enabling USART of PIC 16f877. To enable USART make bit#7 (SPEN) high. I loaded 0x90 in RCSTA. Which enables our serial port and continuously receives data from PC.

RCSTA Register Bits —– Pic16f87X series

Set the Baud Rate in SPBRG Register. Their are two formulas for Baud Rates Calculation. Depending on the BRGH bit of TXSTA Register. Formula for BRGH=1 is Different for BRGH=0. Since this bit BRGH selects High or Low Baud Rates thats why Baud Rate depends on this bit.

Pic16f877 baud rate formula

I loaded 0x81 hexadecimal in it. Its equivalent binary is 10000001 and decimal value is 129. Since mine BRGH bit is high so by using the formula for BRGH=1 the Baud Rate value for 9600 is 129. Loading the value 129 in SPBRG and keeping BRGH=1 sets our Baud Rate to 9600.

The data received at RX pin is placed in RCREG register. When any byte is received, RCREG register becomes full and it raises RCIF(Receive interrupt flag) flag of PIR1 register. When RCIF flag becomes high i pick data from RCREG register. This logic is implemented in while(1) loop. While one continuously receive data from PC.

Download the project files, simulation and Code(c,hex). Code is written in C Language. MPLAB-Ide is used for writing code and High Tech C-Compiler is used for compiling code. Simulation is made in Proteaus 8.0. Plz Give us your feed back on the post.