comm problem

[[email protected]]

Hi all,

I am working on led display project,
i am using AT89S53(8051) for programming(keil C) . from last three
days i
am facing serious problem with communication. I want to communicate PC
to LED
there is another IC on board provided me, that is MAX1487 and there
are only two wire conneting(RXD,TXD) to it. iam connectint only two
wire from com port.

problem is that i am not able to read or write data from SBUF even
keil debugger is going write but there is no hardware response. my
progamme setting for this is as follows:

void main(void)
{
SCON=0X50;
ET2=1;
TCLK=1;
RCLK=1;
C_T2=0;
RCAP2H=0XFF; //baud rate 9600
RCAP2L=0XB2;
TR2=1;
TR1=1;
PS=0;
ES=1;
EA=1;
RI=0;
SM2=0;
}

void rxd(void) interrupt 4
{
unsigned char UART_DATA;

if(RI==1)
{
RI=0;
TR2=0;
UART_DATA=SBUF;
}
}

is this write???????
SBUF is not working well.
is there any programmatic error plese help me to right it

I have additional code for displaying charcter on led in function
main() as well as in rxd(). i am sending you only the settings.

is there any requirment of reg52.h ,reg53.h,regs58.h i have included
first two in code.

there is no right response from led. I think there is communication
error from PC to MAX1487 or MAX1487 to microcontroller!!!!!!!

plese help me if you have idea of MAX1487 pins connection with
microcontroller.
i am using 9600,N,8,1.

 

[sprocket]

I am working on led display project,
.. from last three
days i
am facing serious problem with communication.

Learn to debug. Start at the beginning, not half way though. Use logic.

(1) Forget about interrupts, too much to go wrong. Poll for the
character ready bit.

(2) Use a scope and a simple terminal program. Make sure handshaking
isn't expected. Does anything come through when you press a key? If you
haven't got a scope, tack a LED/ resistor on the receive buffer output.
Does it blink? Then go out and get a scope.

(3) When nothing happens, check that the port is connected the right way
round, the ground to the right pin etc.

(4) Only when you are sure bits are getting though (and back- tack in a
loopback link, but remember to take it off again later) should you
bother with software. Get it to transmit a continuous stream of
somethings - U's say, because that's alternating bits so you can see the
baud rate on a scope. Do they go out, at the right speed? Can you see
them on the terminal screen?

(5) Then change the program to send back whatever is received. Get that
bit working, NOW change to interrupt and get that working. Spend some
time writing naughty words to make sure it works.

(6) Then you are ready to control whatever you wanted to.

This is so general that I'm amazed that everyone needs to be taught it,
I would have thought that the first thing you do in school, or the
beginner's project, would start with this. Start from the hardware, make
sure that's right, then bring in the software a bit at a time, working
from simple to complicated. Only populate the bits of board that are
necessary to get the thing working- and if you are doing a PSU, only
populate that so when the full 24V comes out because you've buggered it
up, it doesn't unstitch all the other expensive ICs on the board.

JS

 

[mpm]

Hi all,

I am working on led display project,
i am using AT89S53(8051) for programming(keil C) . from last three

I don't have the S53 datasheet handy, but make sure there's not a bit
in one of the Special Function registers to enable the serial port /
Timer 2 clock (T2CON would be a good place to start).

A similar 8051 derivative had this feature and it nearly drove me
crazy until I spotted it.
On a legacy 8051 device, the serial ports generally don't have
separate enable bits for the receivers....

Otherwise, it's worth mentioning that you might have the serial logic
(voltages) inverted.
Depends on your circuit. I did not verify your capture/reload as I
would need to know the crystal/timebase for that. So double-check
that, as needed.

Good luck.
-mpm

 

[Hot Jock]

On 07/05/2008 [email protected] wrote:

..
..

there is another IC on board provided me, that is MAX1487 and there
are only two wire conneting(RXD,TXD) to it. iam connectint only two
wire from com port.

..
..

It doesn't matter how much code you write, either good or bad. If you
don't have a ground reference between the com port and your system,
nothing will work.

Try asking in 'sci.electronics.basics' for an explanation of the term
'Ground Reference'.

 

[Martin Griffith]

I don't have the S53 datasheet handy, but make sure there's not a bit
in one of the Special Function registers to enable the serial port /
Timer 2 clock (T2CON would be a good place to start).

A similar 8051 derivative had this feature and it nearly drove me
crazy until I spotted it.
On a legacy 8051 device, the serial ports generally don't have
separate enable bits for the receivers....

Otherwise, it's worth mentioning that you might have the serial logic
(voltages) inverted.
Depends on your circuit. I did not verify your capture/reload as I
would need to know the crystal/timebase for that. So double-check
that, as needed.

Good luck.
-mpm

On the atmel 1995 ed book of the 89xxx it's the REN in SCON, 0x10


martin