Serial communication between 8051 and PC

[fubuaks]

I am trying to send data serially from AT89s52 to PC using hyperterminal. But nothing is being displayed on the hyperterminal screen.

The code with which i've programmed the uc is:

MOV TMOD,20H
MOV TH1,#-3
MOV SCON,#50H
SETB TR1
AGAIN: MOV SBUF,#'Y'
HERE: JNB TI,HERE
CLR TI
SJMP AGAIN

The baud rate of PC is 9600 and i have used MAX232 IC for RS232 to TTL conversion.

My doubts are:

-Can I use normal single strand wires for connecting PC and MAX232.
-In the hyperterminal window i am getting Auto detect instead of 9600 8-n-1


my cnxns are:

8051 max232 RS232
11 to 11-14 to 2
10 to 12-13 to 3

pin no 5of RS232 to gnd

 

[colin mac]

You,re moving the contents of 20H into TMOD, not the value. Should be

MOV TMOD,#20H

 

[fubuaks]

Thnx......now i am getting some arbitrary characters on hyper terminal screen. even if i send a binary value i get those same chars.
Please help me wid this prob.......

 

[colin mac]

Post your circuit diagram with the exact max232 chip you're using, and your code.

 

[fubuaks]

Circuit and snaps

The Max 232 chip is H1N232CPZ. uc is AT89s52. The hyperterminal screen shot is also attached. the code is:


MOV TMOD,#20H
MOV TH1,#-3
MOV SCON,#50H
SETB TR1
AGAIN: MOV SBUF,#'Y'
HERE: JNB TI,HERE
CLR TI
SJMP AGAIN

 

[ericgibbs]

hi,
The text describes a MAX233 which does not require external capacitors, IF you are using a MAX232 you must add the 4 capacitors.

 

[fubuaks]

No, It is max232. Check the datasheet at this link: https://www.electro-tech-online.com/custompdfs/2010/01/fn3138.pdf

 

[rushi53]

Its the problem with "Baud Rate"

What is the value of Crystal Frequency ?


For PC you have used Baud Rate =9600

To get 9600 BR for microcontroller with TH1 = -3, you have to use Crystal freq = 11.0592 MHz

 

[fubuaks]

I've done xactly same......

 

[adari_raju]

hi,
I am new to micro controller.can u pls tell how to perform communicate between pc and micro controller using visual basic 6

 

[adari_raju]

hi,
I am new to micro controller.can u pls tell how to perform communicate between pc and micro controller using visual basic 6

 

[rikilshah]

Use X-CTU terminal which displays Hex values also.

 

[fubuaks]

thanks all for your replies.....i got the thingz correct now.....i was using a 12MHz crystal and assuming it same as a 11.0592MHz one.......silly!

 

[rushi53]

thanks all for your replies.....i got the thingz correct now.....i was using a 12MHz crystal and assuming it same as a 11.0592MHz one.......silly!

Good that ur circuit is working now...
You will learn from your own mistakes...

Carry on!!!