Xbee UART between PICs

[Vizier87]

hi guys,
Back to business for me after learning heaps of optical circuits (but my programming still stinks )

I connected an Xbee to both my uCs, 877A as a transmitter and 4455 as a receiver. I powered my Xbees up using a 3.3V regulator, and the rest is pretty much direct I suppose.

I checked the output of the transmitter using an O-Scope and got a nice square wave, and the same square wave at the receiver end. So i suppose the program's the one making the problem.

It's all simple: The received data will be displayed at PORTD. So far I received nothing.

Here's the transmitter (PIC16f877A):

void main() {

 adcon1=0b00000111;  //pcfg settings: all digital I/O
 cmcon= 0b00000111;  //comparators off
 cvrcon=0;           //voltage comparators off
 txsta=0b00000100;   //8-bit, Async mode, Hi-Speed,
 intcon=0b11000000;  //enable all peripheral interrupts
 spbrg=129;           //9.6 kBps

 trise=0x07;         //porte=input, pspmode_bit=0;
 trisa=0b100000;     //ra5=input
 trisd=0xff;         //rd4=input, rest output
 trisb=0;            //portb=output
 trisc=0b10111111;   //input for keypads and RX=input/TX=0utput

 spen_bit=1;        // serial port enable
 portb=0;
 porta=0;
 



   while (1){
   
        txreg=0xAA;
        txen_bit=1;

   }
}

The receiver is a PIC18F4455:

void main() {

trisd=0;
latd=0;

spen_bit=1; //enable rx-tx
rx9_bit=0;  //8-bit
cren_bit=1;//enable receiver



sync_bit=0;        //asynchronous mode selected
brgh_bit=1;        //hi-speed
brg16_bit=0;       //16-bit not selected

trisc=0b10000000; // rc7=input
intcon=0b11000000; //enable all interrupts

spbrg=129;         //9.6 kbps
  
while (1){

      rcreg=portd;

  }
}

Appreciate the time spent on this. Thanks.

Vizier87.

 

[Ian Rogers]

??????

while (1){
rcreg=portd;
}

If this is the receiver.. shouldn't it be the other way round.

 

[Vizier87]

okay, I've exchanged it. But it keeps getting "garbage" i.e PORTD keeps changing outputs, and even if I didn't turn the transmitter on, it retains it's state.

How do I improve the receiving quality?

 

[Ian Rogers]

How far apart are the modules...... with any kind of aerial, they should be at least a metre away...

I ALWAYS test on a PC first.. just to be sure they are talking ( and they are setup correctly) have you downloaded X-CTU, to check they are on the same PANID ?

 

[Vizier87]

err you mean we have to "setup" these things through PC first? I thought's they're just like other modules?

So.... basically I have to build the FTDI-wired-to-the-Xbee circuit first to configure it, is it?

Thanks dude...

 

[Vizier87]

they should be at least a metre away...

I thought the nearer they are, the better? Pardon for my ignorance... this is a revelation for me.

 

[Ian Rogers]

If they are too close, the signal saturates....

 

[Vizier87]

Also, you mean we have to "setup" these things through PC first? I thought's they're just like other modules?

Basically I have to build the FTDI-wired-to-the-Xbee circuit first to configure it, is it?

Thanks Ian.

 

[Ian Rogers]

I bought one of these

 

[Vizier87]

so if the X-CTU doesn't set it up, the Xbee wouldn't work properly, is it? Or is it just to check the transmissibility?

 

[Ian Rogers]

All I know is that the X-CTU detects what software is on the module (there is quite a few versions) and lets you make a pair.. You set up the speed (baud) and then put them on the same PANID.. then you can tell them which module to talk to.... Download the manual and have a read. These things do a whole lot more.

Also check out XRF modules... They are plug and play, and you can set up networks... They are pin compatible to the xbee.

 

[Vizier87]

allright dude. thanks for the input. I'm going nuts modifying the code anyway so I'm gonna give this a shot, God willing.