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A mistake I see in the code is: escreve="olda";

You cannot treat a string (field) like a variable - you need to use eg strcpy(escreve,"olda") ;

or better initialize like thi ...

Actually the 'data sheet' has _nothing_ to do with the capacitor values that should be used, unless you are using exactly the crystal models recommended by Microchip....
The _crystal_ will have a spe ...

I am using 22pF for 4MHz and I did not change them for 20MHz. Do I need to ?

Check the data sheet first! And then try if the values given by the data sheet work with you project or not - if not -yo ...

Er. That will stop the chip running. MCLR needs to be pulled _up_, not to GND.

Best Wishes

Yes, my mistake - you are right. The resistor to the power line (eg 5V) and not to GND.

so, i just n ...

Er. That will stop the chip running. MCLR needs to be pulled _up_, not to GND.

Best Wishes

Yes, my mistake - you are right. The resistor to the power line (eg 5V) and not to GND.

Next to a possible GND-problem you may not have put a 0.1µF capacitor between Vdd and Vss or the MCLR-pin is not connected/set properly.

the MCLR-pin connected correctly i test it But i did not pu ...

Q2: which cellphone do you use? Did you check the cell-phone serial communication parameters/protocol, esp the electrical levels of the comm-lines and the hand-shake protocols?

the Cell phone is T6 ...

Next to a possible GND-problem you may not have put a 0.1µF capacitor between Vdd and Vss or the MCLR-pin is not connected/set properly.

the MCLR-pin connected correctly i test it But i did not pu ...

Q2: which cellphone do you use? Did you check the cell-phone serial communication parameters/protocol, esp the electrical levels of the comm-lines and the hand-shake protocols?

Next to a possible GND-problem you may not have put a 0.1µF capacitor between Vdd and Vss or the MCLR-pin is not connected/set properly.

Hi , the code cannot work at all. On the receiver side I suggest to use an ISR to catch any incoming data and interpret them in the main function in the while(1)-loop.

As already mentioned: on the ...

This will work for the beginning:

void main()
{

set_tris_c(0b10000000);

enable_interrupts(int_rda);
enable_interrupts(global);

while(1)
{
if (rx=='A')
{
putc( ...

just another tip: don´t use any delays in the interrupt service routines - keep them as short as possible and do most of the work in the main-function

you must enable the interrupts - I added this to the code

Try following (when you press the capital A the LED will turn on - press any other character to turn it off:

#include <16F877A.h>
#fuses HS, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use ...