Software UART: (Page#118)
The C18 library also consists of functions to create a software UART. Like before pin assignments(for TX and RX) need to be made in the header file sw_uart.h present in the h subfolder of the compiler installation. For this function also, there are 3 delay functions that need be defined from which Baudrate is determined. Like before, the functions used require that their corresponding source files present in MCC18\src\pmc_common\SW_UART be included in the project. It consists of the following functions:
OpenUART():
This function configures the TX and RX pins for the PIC.
putcUART(arguments)/ WriteUART(arguments):
Thesefunctions is used serially transmit a byte of data.
putsUART(arguments):
This function is used serially transmit a string.
getcUART()/ReadUART():
These functions are used to read a byte of data from the software UART.
getsUART():
This function is used to read a string from the software UART.
Here is the code(requires additional files to be added in the project, download the whole folder from the link):
Code
//This is a program that demonstrates the use of software UART with
//Microchips Libraries.It simply sends "Hello World!"
//BR=4800,No Parity,1 Stop Bit
//The software UART Section is documented on P#118 of C18 Libraries
//Use 181320Basic.DSN
//Uses RA6 for TX and RA7 for RX
//Add writUART.openuart,readuart in your project.
#include<p18f1320.h>// Include files and definitions for the Processor
#include <sw_uart.h>// Include function definitions for the software USART library
#include<delays.h>// // Include function definitions for built in Delay routines
#pragma config OSC=INTIO2,WDT=OFF,LVP=OFF// Configuration settings
void main(void)
{
unsigned char data[]="Hello World!";
unsigned char message[]="Type an S to start receiving data";
unsigned char readcode;
OSCCON=0b01100000;//Internal 4MHz oscillator
ADCON1=0x7F;//Make all pins Digital
OpenUART();// Configure the output pin for Transmitting
putsUART(message);// Send introduction message
while(1)// Loop forever
{
readcode=ReadUART();// Read from RX pin
if(readcode=='S')// If read code = S
putsUART(data);// Send Data
}
}
// As indicated in the C18 libraries manual
// These 3 Delays determine your Baud Rate
// Refer to Page 118 for the MPLAB C18 Libarries Document for more detail
/****************************************************************/
// DelayTXBitUART =((((2*FOSC)/(4*baud))+1)/2)-12 cycles
// =((((2*4Mhz)/(4*4800))+1)/2)-12 cycles
// =(((8Mhz/19200)+1)/2)-12 cycles
// =((416.66+1)/2)-12 cycles
// =(417.66/2)-12 cycles
// =208.83-12 cycles
// =196.83~197 cycles
/****************************************************************/
void DelayTXBitUART(void)
{
Delay10TCYx(19);
_asm NOP _endasm
_asm NOP _endasm
_asm NOP _endasm
_asm NOP _endasm
_asm NOP _endasm
_asm NOP _endasm
_asm NOP _endasm
}
/****************************************************************/
// DelayRXHalfBitUART =((((2*FOSC)/(8*baud))+1)/2)-9 cycles
// =((((2*4Mhz)/(8*4800)+1)/2)-9 cycles
// =((8Mhz/38400)+1)/2)-9 cycles
// =(208.33+1)/2)-9 cycles
// =(209.33/2)-9 cycles
// =104.66-9 cycles
// =95.66~96 cycles
/****************************************************************/
void DelayRXHalfBitUART(void)
{
Delay10TCYx(9);
_asm NOP _endasm
_asm NOP _endasm
_asm NOP _endasm
_asm NOP _endasm
_asm NOP _endasm
_asm NOP _endasm
}
/****************************************************************/
// DelayRXBitUART =((((2*FOSC)/(4*baud))+1)/2)-14 cycles
// =(((2*4Mhz)/(4*4800)+1)/2)-14 cycles
// =208.83-14 cycles
// =194.83~195 cycles
/****************************************************************/
void DelayRXBitUART(void)
{
Delay10TCYx(19);
_asm NOP _endasm
_asm NOP _endasm
_asm NOP _endasm
_asm NOP _endasm
_asm NOP _endasm
}
The code for the Software UART functions and the additional files required to run it can be downloaded from: