information for connect RS232 by PIC16F877A

can anyone tell me why when i connect to PC Serial Port pin2 the voltage lose?
from 4.2V to 0.3V?

Your question is unclear. Which voltage drops?

Did you set up the hardware correctly?

sorry about that.
i follow this circuit but i using 4 4.7uF connect with max232.
max232 tx output is 4.2V, but when i connect to PC serial pin 2 voltage become 0.3V only.
and PC serial pin 3 voltage actually is how much?
i using multimeter measure is -10V when connect with my max232 become -9V is it correct?

i think your multimeter battery is not working properly change it and check the voltage again.......

the multimeter can function...
i try 3 PC same voltage also...

if the multimeter battery gone weak then it shows higher voltage, so batter you change the battery of the multimeter and see...

i use 2 multimeter to measure same value also too...
could the problem is about the capacitor value?
coz i using 4.7uF.
if i change to 10uF will get different result?

in max232 connection, u are using the 4.7uF instead of 10uF

yup...
because i saw 1 micro controller book circuit is 4.7uF

can u post your full circuit

this is the circuit

change the capacitor from 4.7uF to 10uF and check the code whether its working properly or not ........

just go through this post for serial transmission code
https://www.edaboard.com/thread268462.html

i connect with 10uF gt leaking voltage from max232

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#define switch PORTB.F1
#define pressed 0

int i;
void main()
{
TRISA = 0xF7;
TRISB = 0xFF;
UART1_Init(9600);
Delay_ms(100);
UART1_Data_Ready();

while(1)
{
if(switch==pressed)
{

PORTA = 0xF7;
Delay_ms(100);


}
else
{
for(i=0;i<30;i++)

{
PORTA = 0xF7;
Delay_ms(100);
PORTA = 0xFF;
Delay_ms(100);
UART1_Write_Text(" ALERT! ");
UART1_Write(10);
UART1_Write(13);
Delay_ms(10);
UART1_Write_Text(" HOUSE 1 ");
UART1_Write(10);
UART1_Write(13);
Delay_ms(10);
UART1_Write_Text(" THIEF BREAK IN! ");
UART1_Write(10);
UART1_Write(13);
Delay_ms(100);

}
}
}
}

this is my code.

can u able to see the output on hyper terminal or not........

Sometimes when I make a mistake of the polarity of the Tan capacitor, the volatge drops.

i see display some computer language...
and my code set as (alert, house1, thief break in)
but cant display...
last time i using pic board connect can function...

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i see display some computer language...
and my code set as (alert, house1, thief break in)
but cant display...
last time i using pic board connect can function...

can u tell me which is compiler using you are using

microC PRO for PIC

check the max232 ic that u are using that may be gone i think..........

what you means max232 gone?