SW and HW UART

Pardon??

www.lmgtfy.com

Who cares about good examples of sw UART, when there exists chips with multiple hw UART?

You need a low baudrate if you want anything else to happen while that sw UART is busy sampling the data line.

I've this Software but have a problem with INT0 interrupt or "getc()" function when I send data to SW-UART.

code:

        //Second SW-ASYNC.UART USING INT0 as detect RX data(start bir)

        #include <stdio.h>
        //#include <AT89C51RC2.H>
        #include <at89c51xD2.h>  //AT89c51ED2
        #include "softuart.h"

        #define buff_size       16

        unsigned char t;
        bit     flag_sw_isr;
        unsigned char xdata test_buff[8]={0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37};
 ////////////////////////////////////////////////////////////////////////////////////////
          unsigned char xdata  rx_sw_buffer[buff_size];
          unsigned char index_sw = 0;
 /*External ISR Rutine*/
          void ext_int0_isr (void) interrupt 0
          {
                flag_sw_isr=0;
                rx_sw_buffer[index_sw]= getc();
                if(++index_sw==buff_size)
                {
                        index_sw=0;
                }
                flag_sw_isr=1;
          }
 /*Delay n-ms time.----------------------------------*/
          void delay_ms(unsigned char ms)
          {
                unsigned int x,y;
                for(x=0;x<ms;x++) for(y=0;y<1275;y++);
          }

void main(void){

    delay_ms(50);
        index_sw=0;
 /*EXT_0 ISR Config bits --------------------------------------------------------*/
        IT0 = 1;   // Configure interrupt 0 for falling edge on /INT0 (P3.2)
        EX0 = 1;   // Enable EX0 Interrupt
        EA = 1;    // Enable Global Interrupt Flag
 /*------------------------------------------------------------------------------*/

        SCON  = 0x50;                   /* SCON: mode 1, 8-bit UART, enable rcvr        */
    TMOD |= 0x20;               /* TMOD: timer 1, mode 2, 8-bit reload          */
    TH1   = 0xFD;               /* TH1: reload value for 9600 baud @ 11.0592MHz */
    TR1   = 1;                  /* TR1: timer 1 run                             */
    TI    = 1;

        printf("1-HW UART;2-SW UART DEMO\n\r");
        printf("test_2 UART_0\n\r");

        for(t=0;t<8;t++)     //for testing SW putc() func.
        {
                putc(test_buff[t]);
        }
        flag_sw_isr=1;
    while(1)
        {
                unsigned char i;
                delay_ms(100);
                if(flag_sw_isr)
                {
                        for(i=0;i<16;i++)
                        {
                                putchar(rx_sw_buffer[i]);
                        }
                }
    }
}
//==============================softuart.h====================================
#ifndef __SOFTUART

#define __SOFTUART

void putc(unsigned char);
unsigned char getc(void);

#endif
//========================softuart.asm=========================================

?SU?PUTC SEGMENT CODE
?SU?GETC SEGMENT CODE

PUBLIC _putc
PUBLIC getc

txd_pin EQU     P3.4            ;Transmit on this pin
rxd_pin EQU     P3.2            ;Receive on this pin

;Formula to calculate the bit time delay constant
;This constant is calculated as: (((crystal/baud)/12) - 5) / 2
;crystal is the frequency of crystal in Hz
;baud is required baudrate
;Please try to keep baudrate below 9600
;to get best results :)

BITTIM  EQU     45;             (((11059200/9600)/12) - 5) / 2

;--------------------------------------------
;To send data serially
;For C programs
;Protype definition:
;               void putc(unsigned char);
;Usage:
;               putc(data);
;Return:
;               This function returns nothing
;
;For Assembly Programs:
;
;Usage:
;       data to be send has to be moved to R7
;       for example:
;               mov R7,#'a'
;               lcall _putc
;--------------------------------------------
RSEG ?SU?PUTC
_putc:
        push ACC
        Push PSW
        mov a,r7
        CLR txd_pin                     ;Drop line for start bit
        MOV R0,#BITTIM          ;Wait full bit-time
        DJNZ R0,$                       ;For START bit
        MOV R1,#8                       ;Send 8 bits
putc1:
        RRC A                           ;Move next bit into carry
        MOV txd_pin,C           ;Write next bit
        MOV R0,#BITTIM          ;Wait full bit-time
        DJNZ R0,$                       ;For DATA bit
        DJNZ R1,putc1           ;write 8 bits
        SETB txd_pin            ;Set line high
        RRC A                           ;Restore ACC contents
        MOV R0,#BITTIM          ;Wait full bit-time
        DJNZ R0,$                       ;For STOP bit
        POP PSW
        pop ACC
        RET

;--------------------------------------------
;To receive data Serially
;If you want to use this routine in your
;C program then define function prototype
; as:
;       unsigned char getc(void);
;
;       Usage:
;               data = getc();
;       Return value:
;               Returns data received
;
;
;If you are using it in assembly program
;       Usage:
;               lcall getc
;       Return:
;               data received is stored in R7
;--------------------------------------------

RSEG ?SU?GETC
getc:
        Push ACC
        Push PSW
        JB rxd_pin,$            ;Wait for start bit
        MOV R0,#BITTIM/2        ;Wait 1/2 bit-time
        DJNZ R0,$               ;To sample in middle
        JB rxd_pin,getc         ;Insure valid
        MOV R1,#8               ;Read 8 bits
getc1:
        MOV R0,#BITTIM          ;Wait full bit-time
        DJNZ R0,$               ;For DATA bit
        MOV C,rxd_pin           ;Read bit
        RRC A                   ;Shift it into ACC
        DJNZ R1,getc1           ;read 8 bits
        mov r7,a
        POP PSW
        pop ACC
        RET                                     ;go home
                END

I've some hardware which I want to use it.

And what problem, exactly, do you have?

When I send data to SW UART (P3.2)INT0 at89c51ed2 "Block" and do nothing until I make RESET or Power OFF -> ON!

Agree with Per, HW solutions should be used. However, if possible.
If it is just for fun and not a commercial product, why not?
But I do not like those endless discussions on forums, there will
be always different opinions, so you may send an personal email
to embedded-world at home dot se. For some questions I do have.
If it helps, o.k., if not, also o.k.
Best regards.

I've some hardware which I want to use it
I have a shoe and want to pound a nail into my wall.

If it is just for fun and not a commercial product, why not?
because the "learning value" is a big fat ZERO

But I do not like those endless discussions on forums, there will
be always different opinions
well, if there were not "different opinions" why have a "discussion forum"

Some read the forum title and assume it reads "solution providing place". Where a 'discussion' most likely will provide help, providiong nicely boxed shrink wrapped solutions is not the purpose.

Erik

Not at all!

Implementing a UART in software requires understanding a lot of things which will be of general use - not least, how a UART actually works!

Any Idea..???