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John Morley
Joined: 09 Aug 2004
Posts: 97
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| trouble with serial input data |
 Posted: Mon Sep 19, 2005 9:59 am |
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Hi all,
I have a number of PIC modules interconnected using an RS485 network. Each module has a unique address assigned by a set of DIP switches, and controls two digital output lines. I am sending the following command string to the modules:
#NX:A,B<CR> where X is the module address (0 to 9), and A and B are the desired digital output states.
At this point I'm just trying to see if I can uniquely command a specific module. My code contains a serial interrupt routine that fills a receive buffer until a CR is received, and then the Main() routine checks for an address match in the received data. I know the CR is being received because I toggle one of the digital outputs (they are connected to LEDs) as a diagnostic, but the address test that follows is never successful....... A putc() of the module address returns an unprintable ASCII character. I think this is just a problem with how the data is represented in the receive buffer. I have a routine (gethexbyte) to handle that, but using it doesn't seem to help the problem. I don't think this is a hardware issue because I have a small test program that uses getc() and putc() to receive and transmit characters. Any one of the modules connected individually works fine.
My compiler version is: 3.162
| Code: |
//-----< Include Files, setup fuses >-----
#include <16f73.h>
#fuses HS, NOWDT, NOPROTECT
//-----< Compiler use statements >-----
// Tell compiler clock speed is 20.00 MHZ Crystal
#use delay(clock=20000000)
//-----< General Program Defines >-----
#define RS232_OUT PIN_A4 // RS232 Output to Terminal
#define RS485_OUT PIN_C6 // RS485 Output Pin
#define RS485_IN PIN_C7 // RS485 Input Pin
#define RS485_Enable PIN_C5 // RS485 Enable Pin
#define Relay1_Out Pin_B0 // Relay 1 Output (active hi, and inverted by output FET)
#define Relay2_Out Pin_B1 // Relay 2 Output (active hi, and inverted by output FET)
//-----< Firmware Version >-----
#define SW_Data1 PIN_C0
#define SW_Data2 PIN_C1
#define SW_Data3 PIN_C2
#define SW_Data4 PIN_C3
#define SW_Data5 PIN_C4
#define CR 0x0d // ASCII Value for a Carriage Return
//-----< Serial Port Definition >-----
#use rs232(baud=9600, xmit=RS232_Out, stream = Console, Restart_WDT, ERRORS)
#use rs232(baud=9600, xmit=RS485_Out, rcv=RS485_In, enable = RS485_Enable, stream = Network, Restart_WDT, ERRORS)
//-----< RS232 Packet definitions >-----
int RX_Command_Ready; // TRUE If a receive packet is ready
#define RX_SIZE 20 // RS485 buffer for serial reception
char RxBuffer[RX_SIZE]; // RS485 serial RX buffer
int Index = 0; // RS485 RX data IN index
int iAddress;
//-----< Get a RS232 command packet >-----
// Note: This routine is interrupt driven. RS485 input takes priority
// over every other operation in the system.
#INT_RDA // Interrupt driven RS485 routine
void rs485_isr(void)
{
char temp; // local data storage
temp = fgetc(Network); // get rx data
// If we got a CR, then the command is completed.
if (temp == CR)
{
RxBuffer[Index] = temp;
RX_Command_Ready = TRUE;
return;
}
// Save the character to the receive buffer.
RxBuffer[Index]=temp;
// Check for buffer overflow.
if ( Index >= (RX_SIZE - 1) )
Index = 0;
else
Index++;
}
// This routine is used to convert characters for checking the checksum
// It simply converts an ASCII hex value into true decimal form
// ASCII allows for a quick and dirty conversion routine!
byte gethexbyte(char digit) {
if(!BIT_TEST(digit,6)) // Its a number if bit 6 is 0
return(digit & 0x0F); // Simple way to convert 0-9
else
return((digit & 0x0F) + 9);
}
void main(void)
{
// Here we read the DIP switch to determine the module network address
iAddress= input(SW_Data1) + ( 2 * input(SW_Data2)) + (4 * input(SW_Data3)) + (8 * input(SW_Data4)) + (16 * input(SW_Data5));
//fPrintf(Network, "Address: %d\n\r",iAddress);
// Here we set the initialize program variables.....
Output_low(Relay1_Out);
Output_low(Relay2_Out);
setup_adc_ports( NO_ANALOGS );
enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);
while(1)
{
// Here we wait for a character to show up in the Rcv buffer, and then read the received string
if ( RX_Command_Ready == TRUE )
{
// Just to be safe, first things first...
disable_interrupts(GLOBAL);
RX_Command_Ready = FALSE;
Output_high(Relay1_Out); //turn on the LED so we know we received a command...
putc(RxBuffer[2], Network);
// Let's start to decode the command if we have the correct address.....
if (gethexbyte(RxBuffer[2]) == iAddress)
{
Output_high(Relay2_Out);
delay_ms(500);
// fprintf(Network, "#N%d:0,0,1234!", iAddress);
delay_ms(500);
Output_low(Relay2_Out);
// decode_command();
}
}
// Done so re-enable RS485
Index = 0;
enable_interrupts(GLOBAL);
} // while
} // end Main
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Does anyone have an idea what might be going on?
Thanks!
John
_________________
John Morley |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Mon Sep 19, 2005 10:48 am |
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| Looks like to me that your index = 0 and enable interrupt statements are in the main loop so index is just about always 0. Also, you need some sort of signal that this is the start of a message. This could be a timeout or a special char recieved or even a break signal. You this to reset the index to 0. |
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John Morley
Joined: 09 Aug 2004
Posts: 97
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| Posted: Mon Sep 19, 2005 6:51 pm |
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Mark,
Yep, I can't believe I did that with Index=0  ....... I was moving some code around and never picked up on the error even after many checks! Also, I added a check for the start character (#) in the interrupt handler and all is well now!
Thanks!
_________________
John Morley |
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