PIC and USART problem

[Cheetos]

I was trying to use USART of my PIC. Is it right that i get 3 volts at my Rx pin and 4 volts at my TX pin??

 

[robinruet]

output always vcc or 0v....use max232 if u want to to serial port of pc.

 

[andre_luis]

I was trying to use USART of my PIC. Is it right that i get 3 volts at my Rx pin and 4 volts at my TX pin??

PIC pins of USART module comunicates at TTL logic level.

+++

 

[engshahrul]

UART is signal 5V and 0V. If you are transmitting data, ofcourse the measured voltage is lower than 5V.

 

[Cheetos]

thank you all for your replies, may i ask what is the problem with my code if this is happening?
this is my code
void main(){
char buff=0; // usart data are char, not float
PORTB = 0x00;
TRISB = 0x00;
TRISC = 0xBF; // only TX pin is made output on port C

Usart_init(9600);

while(1){

if(Usart_Data_Ready()){
buff=Usart_Read();
Usart_Write(buff);


}
}

}

plus this is what my zigbee schematics look like the pin headers are connected to rx and tx of my PIC. Initially without the xbee, the Vcc reading is 3.33 volts. When i attach the xbee module it goes down to 3.0 volts, what can be the problem?

 

[emresel]

waht is your vcc? 5V or 3v3?
Your zigbee module might be loading your pics IOs. You can use series resistor on those lines around 100-220ohms.
By the way RX may need a pull up resistor to VCC.

 

[Cheetos]

the vout of the regulator is 5V, the resistance values of each resistors are 4.7k. i took the voltage before R2 that gives me 3.3V. another thing, when i disconnect the connection at rx and tx between my pic and zigbee and with my zigbee attached to that circuit, it gives me a reading of 1.8V.