Serial Data Transfer to PC(Personal Computer) using PIC16f877 Microcontroller USART

Here is a simple project on How to transmit serial data to pc using built in usart(universal Syncronous-Asyncronous receiver transmitter)of PIC 16f877 microcontroller. The data Transmitted by PIC microcontroller is received by computer through its (Serial)DB-9 Port and is displayed on Hyperterminal window. Since microcontrollers works on TTL wave form and standard PC(Personal Computers) works on RS-232 wave form so we have to convert our transmitted data from microcontroller into RS-232 wave form. The best way is to use MAX-232 ic. It converts TTL wave form in to RS-232 and RS-232 to TTL.To learn about its Pin out and working below is a good tutorial.

MAX-232 PIN CONFIGURATION AND WORKING.

TTL to RS-232C Level wave form

The TX or transmission line of Usart is at pin 25 of PIC 16f877. Connect this transmission line to pin 10(T2IN) of MAX-232. Connect Pin# 7(T2OUT) of MAX-232 to pin# 2 of DB-9 port of your PC. Connect four Capacitors to MAX-232. The Capacitors should range between 1uf to 10uf. I recommend 10uf because i used it in mine project and the circuit is working fine. Apply 5v to vcc pin of microcontroller and MAx-232. Ground Gnd pins of microcontroller and MAX-232. Inserst 20MHz crystal between pins 13 and 14 of PIC 16f877. Crystal should be in parallel to two 33Pf capacitors.The circuit diagram of the project is below.

Serial Data Transmission to PC(Personal Computer- Hyperterminal Program) using PIC16f877A USART

Once you know about the registers associated with Usart transmission you can easily understand the code below.
First of all to enable the serial port or TX(Transmission) RX(Reception) line. The SPEN(Serial port enable bit) bit of register RCSTA(Receive status and control register) should be high.

SPEN Bit of RCTA Register of PICC16f877 Microcontroller- SPEN enables Serial Port of PIC16f877 microcontroller

I loaded 0x80 in RCSTA register. Which is hexadecimal value. Its equivalent binary form is 10000000. This value is loaded in RCSTA register. Which only sets Serial Port Enabled.

RCSTA Register Bits

All the other bits are reception bits. Since i am concerned only with Transmission so i only need to enable serial port.

Set the Transmission setting in TXSTA(Transmit Status and Control Register) register.

TXSTA register of PIC16f877 Microcontroller

I loaded 0x06 in TXSTA. 0x06 is hexadecimal value its equivalent binary is 00000110.

TXSTA Register Bits

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.

PIC 16f877 Baud Rate Calculation 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 Which you want to transmit should be placed in TXREG(Transmit register) register. This register gives data to TSR Register. TSR then transmits the data serialy. TSR Register is not available for user you can not access it.

I write code in MP-Lab using High Tech C Compiler. The code is written in c language. First import the library htc.h. Always import this library in each project if you are writting code using high tech c compiler. Then Crystal frequency in defined. which is 20 MHz. In the main function first TRISC6=0 statement makes the Port-C bit 6 as output
pin. This pin is actually Multiplexed pin. It can be used as Digital I/O as well as TX line. So first make it as output pin. Then a string Array is defined. This Array contains my website name “www.microcontroller-project.com”. This String is displayed on Hyperterminal screen when the program runs. Then the registers are initialized i explaned their initialization above.
While 1 loop is continuously printing my website name on hyperterminal. While(TRMT=0) statement checks if the TSR Register is empty. If TSR is full The control remains on while(TRMT=0) statement and when TSR becomes empty. TRMT becomes 1 and control jumps to next statement.

Before running the program. Just set the hperterminal.Goto Start->Programs->Accessories->Communications>HyperTerminal open new connection, name it what ever you want then click ok. Now a window appears select COM1 from connect using drop down menu click ok. Now set COM1 properties, bits per second as you specified in your program in mine case 9600, Data bits=8, Parity=none, Stop bits=1, Flow control=none then click ok. Now switch on the power of your circuit, you will see “www.microcontroller-project.com” on Hyperterminal screen.

Download the project files with code and simulation. Code is written in c language and simulation is made in proteaus. Please Give us your feed back on the project.

serial transmission using Pic16f877 USART