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jmaurin
Joined: 29 Mar 2008
Posts: 26
Location: Ribeirão Preto, SP, Brasil
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| Help with serial communication |
 Posted: Wed Oct 08, 2008 8:38 pm |
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Hi all.
I need some help with serial communication. I'm using serial do communicate 2 PIC's (A=16F628 and B=18F4550). Ok, I can send and receive data.
The 628 is just a 'video board' while 4550 is the main processor.
The thing is: 628 receive data from serial and send to my car displays.
The problem: I need to send data as soon as possible (every 1ms is is possible).
If I put a 'while' in my pic and always send data to my car display, everything works fine...
The problem: I need to get data from 4550 and send to car's display.
In the main while of 628 I have something like this:
| Code: |
while(1) {
if (pin5==1) { // Main processor is on
gets(temp); // I need a full string not a single char
Display(temp);
} else {
Display("Main processor of");
}
}
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The problem is: if I delay to send the text (500ms for example), my main loop will break until serial data is received....and I can't do that! I need to always send data to my car.
I tried to use "if (kbhit()) then gets(temp)", but I'm getting a lot of garbage data. Why?
I'm sending strings with
| Code: | void Manda(char *text) {
fprintf(rs1,"%s\r",text);
return;
}
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With only gets() everything works, but main loop wait until data received...
I also tried to use "timed out getc" from examples, but didn't work (program still waiting).
Any help?? Tks! |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Posted: Thu Oct 09, 2008 12:45 am |
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Hello,
if you think about, you'll see, that it can't work this way.
If you're not able to await the reception of a complete string (you aren't), then you can only receive single characters to a buffer. If the lineend is detected, the buffered data can be processed. If time consuming actions are intended concurrent to the character reception, it's best to perform the receive in an interrupt function. The processing of incoming data should be done in the main loop.
Regards,
Frank |
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Guest
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| Posted: Thu Oct 09, 2008 10:52 am |
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ok, let's see if i'm right with this new idea (about what you said):
In the main loop, i'll always output to my car's display the content of var 'text'.
Then, i use an interrupt called when a char is received. If char != 13 (\r), then i just concat to var 'text_temp'. When i got char 13, then i transfer 'text_temp' to 'text' so the new text is displayed on the car's display.
That's it?
I didn't remember about interrupts to receive chars...thks! i'll try this. |
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