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hussain_kiet
Joined: 22 Sep 2008
Posts: 6
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| PIC to PIC serial communication |
 Posted: Sat Dec 06, 2008 1:24 am |
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Hi this is hussain,
I am doing a project in which I need to share data between two
PIC16F877's serially.
The first PIC is sending the data via virtual serial while the 2nd one receives the data on its hardware serial.
But the 2nd one does not receive the data correctly.
I don't have any idea about whether the 1st one is not sending the data correctly or the 2nd one doesn't receive correctly ?
Anyone can give me any idea of what is going wrong ?
Thanks in advance.
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!!!!...HUSSAIN AFTAB...!!!! |
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Rohit de Sa
Joined: 09 Nov 2007
Posts: 282
Location: India
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| Posted: Sat Dec 06, 2008 5:53 am |
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| Quote: | | The first PIC is sending the data via virtual serial |
Do you mean software serial?
A way to troubleshoot this problem would be to individually test the two PICs - try to localize the problem. Use a PC as a tester. Connect the transmitting PIC to a PC and check if you receive valid data on a terminal program (Hyperterminal or SIOW).
Next, connect the receiver PIC to the PC and check if you can transmit data from the PC to it successfully.
Software serial has several configurable options. It is up to you to make sure the options are valid and appropriate.
Make sure the baud rates on both devices are the same. Make sure the data lines are connected correctly (RX1 to TX2 and TX1 to RX2). Make sure a ground wire is connected between the two PICs.
Rohit |
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hussain_kiet
Joined: 22 Sep 2008
Posts: 6
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| Posted: Sat Dec 06, 2008 10:58 am |
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Yes I definitely mean software serial!!!
I've checked the baud rates, ground wire is common of both PIC's.
I've checked receiving of 2nd PIC, but when I transmit through the 1st PIC (through software serial) and check the data at the hyperterminal it shows wrong data, but the trend was always similar, means if transmit "A"
then it will receive something else but it will always remains same!!
Hope you understand what I meant to say. 
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!!!!...HUSSAIN AFTAB...!!!! |
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Ttelmah
Guest
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| Posted: Sat Dec 06, 2008 1:50 pm |
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Start by testing the clock speed of both chips.
Use a program that just raises a line for a time interval, and drops it again. If you have a reasonably well calibrated scope, then use a short interval like 100mSec, and time the pulse with your scope. If not, use a much longer time like 10 seconds, and time the pulse with a stopwatch. If the times from either chip is wrong, then this is the problem. Verify that your crystals, do match the clock rates entered in the clock statements on each chip. This sort of basic timing, needs to be 'right', before serial can work.
Second comment. Is the chip doing anything else while sending the character on the software serial?. Do you have any interrupts running?. If so, then this is the problem. Sotware async serial as implemented by CCS, requires that the processor does basically nothing else during the transmission (or reception) of a character using the software port.
What baud rate, start bit, stop bit etc., are you using?.
Best Wishes |
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Rohit de Sa
Joined: 09 Nov 2007
Posts: 282
Location: India
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| Posted: Sat Dec 06, 2008 11:45 pm |
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So its the PIC running software serial that's giving erroneous data? Make sure that the crystal that you use and the #use delay statement tally.
Also post your code.
Rohit |
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adanali
Guest
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| pic to pc serial communication |
| Posted: Sun Jan 11, 2009 12:27 am |
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Hi all,
I also have this problem and my code is:
| Code: | #include "16f877a.H"
#use rs232(baud=9600, XMIT=PIN_C6,RCV=PIN_C7,STREAM=COMA,ERRORS)
#use rs232(baud=9600, XMIT=PIN_B2,RCV=PIN_B3,STREAM=COMB) |
Pic A:
| Code: | while(TRUE)
{
putc('B',COM_A);
if(kbhit(COM_A)){
c=getc(COM_A);
putc(c,COM_B)
}
} |
Pic B:
| Code: | while(TRUE)
{
putc('B',COM_A);
if(kbhit(COM_A)){
c=getc(COM_A);
putc(c,COM_B)
}
} |
the problem is code or something from hardware i couldn't understand.
Is it why because i am using hardware and software serial together? |
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adanali
Guest
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| pic to pc serial communication |
| Posted: Sun Jan 11, 2009 12:29 am |
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sorry the PIC B code will be :
| Code: | while(TRUE)
{
putc('A',COM_A);
if(kbhit(COM_A)){
c=getc(COM_A);
putc(c,COM_B)
}
} |
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SherpaDoug
Joined: 07 Sep 2003
Posts: 1640
Location: Cape Cod Mass USA
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| Posted: Sun Jan 11, 2009 11:12 am |
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Did you try what Rohit de Sa suggested? Does either PIC say the right thing to a PC? If not, do they say anything at all? Is it repeatable. It would be best to post a whole test program. Something we can compile and run.
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