Please help me with my problem...T_T

[Bengt]

See wikipedia for the voltage levels of RS232 and you will understand the problem. RS-232 - Wikipedia, the free encyclopediaHowever, it IS possible to connect a single supply circuit without a proper level shifter. If you only transfer data from PC to circuit, it is easy as you don't have t bother about the problem about generating a negative signal and that is the reason the simple circuit nifleheim13 showed is working. The input signals (1 and 0) are both to big (1=15V, 0=-15V) and the only thing you need to do is to use current limit. It is R2=22 kohm that do this. So, level shifter = one resister. Cheap and good performance.
If you need to transfer data TO the PC it is more complicated as the circuit can not generate the high voltage signals and that is the reason we need a level shifter. If you going very slow it should be possible to use a combination of current limiting and pull-up/pull down but it is not worth the effort.

 

[nifleheim13]

i only need the pc to send data to the pic through the rs232 port.....so i tried to use that simple circuit.....i use the hex file that was included on the software i posted last time and it's working.....then i tried to use the program posted last time using mikroBasic and it doesn't work...i also tried changing the baud rate and also making it inverted....i don't know what's wrong....

 

[lockman_akim]

If you going very slow it should be possible to use a combination of current limiting and pull-up/pull down but it is not worth the effort.

yes i agree with him it like you are building your own max232...why u cant use that max232?

 

[Bengt]

A resistor is simpler than a circuit, thats why. Less things that can go wrong.

 

[nifleheim13]

i already managed to receive data from rs232 to PIC16F84A with just the 22k ohm resistor.....i just added a while condition to Tahmid's code and i inverted it.....now i'm trying to send data from the PIC to another PIC.....