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LordFrith
Joined: 05 Jul 2006
Posts: 3
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| bkbhit is true but nothing connected to the serial port!?!?! |
 Posted: Mon Sep 18, 2006 5:57 am |
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Hi
Scenario:
PIC16F73
1 x HW UART
1 x SW UART
Using sample code for int_rda.
Problem:
When I run the code, bkbhit returns true but garbage in the buffer and nothing is connected to the serial port?!?!?
| Code: |
#include <16F73.h>
#include "stdio.h"
#pragma type short=8,int=16,long=32
//*******************************
//***** *****
//***** GLOBAL VARAIABLES *****
//***** *****
//*******************************
#fuses HS,NOWDT,NOPROTECT,NOBROWNOUT,NOPUT
#define EEPROM_SDA PIN_C4
#define EEPROM_SCL PIN_C3
#use delay(clock=16000000)
#use i2c(master,sda=EEPROM_SDA, scl=EEPROM_SCL)
#use rs232(baud=4800, xmit=PIN_C6, rcv=PIN_C7, STREAM=MDM, ERRORS)
#use rs232(baud=4800, xmit=PIN_A3, rcv=PIN_A2, STREAM=DBG)
// PIC registers
#byte PORTA = 0x05
#byte PORTB = 0x06
#byte PORTC = 0x07
#byte ADRES = 0x1e
#byte ADCON0 = 0x1f
#byte ADCON1 = 0x9f
#byte OPTION = 0x81
#byte INTCON = 0x0b
#byte TMR0 = 0x01
#bit EDGE_BIT = OPTION.6
#bit E_B = intcon.4
#bit C_B = intcon.1
#define BUFFER_SIZE 16
BYTE buffer[BUFFER_SIZE];
BYTE next_in = 0;
BYTE next_out = 0;
#define bkbhit (next_in!=next_out)
BYTE bgetc() {
BYTE c;
while(!bkbhit) ;
c=buffer[next_out];
next_out=(next_out+1) % BUFFER_SIZE;
return(c);
}
#int_rda
void read_serial()
{
int t;
buffer[next_in]=fgetc(MDM);
t=next_in;
next_in=(next_in+1) % BUFFER_SIZE;
if(next_in==next_out)
next_in=t; // Buffer full !!
}
<!--- SNIP --->
fprintf(DBG, "(Turning on modem power)\r\n" );
DIGOUT_MOD_PWR = ON;
enable_interrupts( GLOBAL );
enable_interrupts( INT_RDA );
delay_ms( 10000 );
while(!bkbhit)
{
delay_us(10);
}
fprintf( DBG, "Data ready!\r\n");
while(bkbhit)
{
fprintf( DBG, "%c", bgetc());
}
// There's a TX bit here
if( boGotFirstModemRespChar( 10, PARAM_RESPONSE ) == FALSE )
{
// but we didn't get one
fprintf(DBG, "(Param Response Timed out)\r\n" );
boReportSendSuccessful = FALSE;
ucHoursToSleep = 1;
goto SendReportErrorExit;
}
<!--- SNIP --->
BYTE boGotFirstModemRespChar( unsigned long ulTimeoutSecs, unsigned char ucExpectedPacketType )
{
unsigned long ulModemRespTimeout10Us;
BYTE boGotFirstChar;
BYTE boWaitingForPcktHdr;
unsigned char ucChar;
unsigned long ulTimeout;
boWaitingForPcktHdr = true;
boGotFirstChar = FALSE;
ulTimeout = ulTimeoutSecs;
fprintf( DBG, "(Waiting for response from modem)\r\n" );
while ( boWaitingForPcktHdr == true )
{
ulModemRespTimeout10Us = 0;
while( !bkbhit && (ulModemRespTimeout10Us < 200000 ))
{
delay_us( 10 );
ulModemRespTimeout10Us++;
}
if ( bkbhit )
{
//fprintf( DBG, "(Something on the rcv buffer)\r\n(" );
ucChar = bgetc();
fprintf( DBG, "%X", ucChar );
if( ucChar == PKT_HEADER )
{
if( bgetc() == ucExpectedPacketType )
{
boGotFirstChar = true;
boWaitingForPcktHdr = False;
}
}
}
ulTimeout--;
if(ulTimeout == 0)
{
boGotFirstChar = FALSE;
boWaitingForPcktHdr = false;
}
}
// fprintf( DBG, ")\r\n" );
return boGotFirstChar;
}
|
Output:
(Turning on modem power)
Data ready!
� <--- where does this come from
TX: 86 12 08 00 00 01 00 9F
(Waiting for response from modem)
C30062180000C080FE <--- where does this come from
(Param Response Timed out)
However...there's nothing connected to the serial port.
Any thoughts? |
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Ttelmah
Guest
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| Posted: Mon Sep 18, 2006 7:19 am |
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'Nothing connected to the serial port', implies the line can float. The '0' at the beginning, implies the line is low here (remember that for serial, the 'idle' state is a high signal). Then the line is floating upwards, so you see garbage.
Best Wishes |
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LordFrith
Joined: 05 Jul 2006
Posts: 3
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| Posted: Mon Sep 18, 2006 7:37 am |
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| Ttelmah wrote: | 'Nothing connected to the serial port', implies the line can float. The '0' at the beginning, implies the line is low here (remember that for serial, the 'idle' state is a high signal). Then the line is floating upwards, so you see garbage.
Best Wishes |
Apologies...the serial port is connected to a hyperterminal session...no data is traversing the line. |
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Ttelmah
Guest
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| Posted: Mon Sep 18, 2006 7:54 am |
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In which case, the zero at the beginning is still normal. (this is because the charge pump in chips like the MAX232, takes a while to get working, and the chip doesn't work properly till this happens. The normal solution is to wait for perhaps 20mSec, then clear the UART, and enable the interrupts. However the 'garbage', is not. How are the units connected?. Good 0v connection?.
Best Wishes |
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LordFrith
Joined: 05 Jul 2006
Posts: 3
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| Posted: Mon Sep 18, 2006 8:00 am |
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| Ttelmah wrote: | In which case, the zero at the beginning is still normal. (this is because the charge pump in chips like the MAX232, takes a while to get working, and the chip doesn't work properly till this happens. The normal solution is to wait for perhaps 20mSec, then clear the UART, and enable the interrupts. However the 'garbage', is not. How are the units connected?. Good 0v connection?.
Best Wishes |
Discovered the problem...had used set_tris_c incorrectly!!!
I've been using set_tris_c(0xFF) to save power but was turning on the outputs with set_tris_c(0x5B) instead of 0x9B
I feel very foolish! |
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