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printf statement not giving the required string out.

arjun pal

Hi All
i want following string of bytes to be send by the CPU 80C51RD2 serial port:0xba,0x02,0x01,0xb9
statement:

printf("%c%c%c%c",stxi,select_lnth,select_cmd_char,select_bcc);
output:0xba,0x02,0x01

why 0xb9 is missing ?

i have tried a long cut method to overcome this
unsigned int loop;
unsigned char buf[4]; 
sprintf(buf,"%c%c%c%c",stxi,select_lnth,select_cmd_char,select_bcc);
for(loop=0;loop<=4;loop++)
  printf("%c",buf[loop]);
Above for statement should have worked with condition "loop<=3",but again last byte was missing.By giving "loop<=4" i got all required bytes.

why "for loop" terminating condition have to be kept at " <=4 " ,when it should have worked with " <=3 " ?

Thanks in advance

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  • 0

    Are you waiting one character time after printf returns to be sure the character is transmitted?

    The printf and putchar functions return before the last character is actually shifted out the serial port.

    If you use the simulator and you set a breakpoint immediately after the printf function exits, the last character will not be sent out the serial port.

    Jon

Reply
  • 0

    Are you waiting one character time after printf returns to be sure the character is transmitted?

    The printf and putchar functions return before the last character is actually shifted out the serial port.

    If you use the simulator and you set a breakpoint immediately after the printf function exits, the last character will not be sent out the serial port.

    Jon

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