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ThomasC
Joined: 09 Oct 2007
Posts: 62
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| RS485 Communication - Error in Output -------SOLVED!!! THX! |
 Posted: Tue Feb 05, 2008 10:09 am |
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I used the example in the "RS485 woes" thread to help establish communication from slave (PIC16F690) to master (Computer).
http://www.ccsinfo.com/forum/viewtopic.php?t=32232
Hardware used:
PCM 4.060--->PIC16F690--->MAX485--->ICD2--->Telebyte Model 245 Opto-Isolated Superverter (RS485 to RS232 converter)--->Windows XP PC Xenon CPU
There is communication between the PIC16F690 and PC. I'm using Comm Operator (a hyperterminal-like program) and set the output to hex.
It is suppoused to show:
12
Hello World!
12
Hello World!
12
Hello World!
In my case, it is showing:
9D 9B E5 EB 6F 35 27 27 21 BF 51 21 1B 27 37 BD E5 EB (HEX)
I do not understand why it comes out differently.
I notice that the output changes when the frequency is increased or decreased. It will even jump to another value for a second before it "stabilizes" on a certain value. Why does it do that? Thanks!
| Code: | #include <16F690.h>
#device adc=10 //Configures the read_adc return size. 10 will return the full A/D reading of 10 bits.
//#fuses INTRC_IO, NOWDT, NOPROTECT, BROWNOUT
#fuses INTRC,NOWDT,NOPROTECT,BROWNOUT,NOMCLR,BROWNOUT,NOIESO,NOFCMEN,PUT
#use delay(clock=4000000)
#define Rx_In PIN_B5 // serial data receive pin
#define Tx_Out PIN_B7 // serial data transmit pin
#define Serial_Enable PIN_C1 // Serial data enable
#use rs232(baud=9600, xmit=Tx_Out, rcv=Rx_In, enable=Serial_Enable, ERRORS, stream=Network)
void Network_fputc(char c)
{
fputc(c, Network);
}
//===============================
void main() {
while(1){
delay_ms(1000);
fputc('1', Network);
fputc('2', Network);
printf(Network_fputc, "\r\nHello World!\r\n");
}
} |
Last edited by ThomasC on Tue Feb 05, 2008 2:55 pm; edited 1 time in total |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Feb 05, 2008 1:22 pm |
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The data that you're getting is inverted and shifted left one bit position,
compared to the source data. I don't understand what you're doing,
but you've got a very long, complex chain of driver/inverters. I suspect
that you've got one un-necessary inversion in there somewhere.
Just as a test, add the FORCE_SW and INVERT parameters to your
#use rs232() statement. See if that fixes it. |
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ThomasC
Joined: 09 Oct 2007
Posts: 62
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| Posted: Tue Feb 05, 2008 2:17 pm |
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I used the FORCE_SW and INVERT, and it fixed it.
The output is now:
12
Hello World!
12
Hello World!
12
Hello World!
12
Hello World!
I must have inverted the wires like you said and once I reversed the wires between the MAX485 and the Telebyte 245 and the output is correct even without using the FORCE_SW and INVERT.
I can't believe it was something this simple. It would would have taken me days to figure out that this was wrong.
I would like to not use all this hardware, but I thought the MAX485 was required for RS485 PIC communication? Then I thought the Telebyte Model 245 Opto-Isolated Superverter was required to hook up the MAX485 to the RS232 port on the PC? If there's a better way I'm open to suggestions. Thanks PCM Programmer. |
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