Hi
I've managed to prune down my code to single/simple one filer that reproduces
the problem.
I'd welcome any suggestions, including what list is the best list to discuss
this sort of problem.
To re-iterate my problem. I send four bytes ( 4 * 0x55) and receive from my
Mac, with Java
as follows:
int cnt=0;
while (true) {
cnt++;
m_OutputStream.write(0x55);
m_OutputStream.write(0x55);
m_OutputStream.write(0x55);
m_OutputStream.write(0x55);
for (int i=0; i<4; ++i) {
int
ch=m_InputStream.read();
if (ch>=0 && ch!=0x55)
System.out.printf("%d %02X\n",cnt, ch);
}
Thread.sleep(50);
}
So it expects that the 55's are echoed back:
The code on the PIC is below. What it does it received characters using
interrupt
and echoes them back. If the character received is not 0x55 it toggles on
output pin,
which I'm monitoring with oscilloscope, as well as the data sent by my Mac.
Running this code generates a lot of toggles on the output pin and on the
Mac console I see errors too. If I add inter character delays on the Mac side
or remove the sending of echos from the PIC code the errors go away.
Baudrate has no effect.
So I'm rather baffled, what am I missing?
br Kusti
Here is the PIC code:
#include <stdio.h>
#include "usart.h"
#include "pic18fregs.h"
code char at 0x300000 CONFIG1L = 0x20; // USBDIV=1, CPUDIV=00, PLLDIV = 000
code char at 0x300001 CONFIG1H = 0x0E; // IESO=0, FCMEN=0, FOSC = 1110
code char at 0x300002 CONFIG2L = 0x20; // Brown out off, PWRT On
code char at 0x300003 CONFIG2H = 0x00; // WDT off
code char at 0x300004 CONFIG3L = 0xff; // Unused configuration bits
code char at 0x300005 CONFIG3H = 0x81; // Yes MCLR, PORTB digital, CCP2 - RC1
code char at 0x300006 CONFIG4L = 0x80; // ICD off, ext off, LVP off, stk ovr off
code char at 0x300007 CONFIG4H = 0xff; // Unused configuration bits
code char at 0x300008 CONFIG5L = 0xff; // No code read protection
code char at 0x300009 CONFIG5H = 0xff; // No data/boot read protection
code char at 0x30000A CONFIG6L = 0xff; // No code write protection
code char at 0x30000B CONFIG6H = 0xff; // No data/boot/table protection
code char at 0x30000C CONFIG7L = 0xff; // No table read protection
code char at 0x30000D CONFIG7H = 0xff; // No boot table protection
#define LED_PIN PORTBbits.RB4
#define LED_TRIS TRISBbits.TRISB4
#define CRITICAL(CODE) do { \
static unsigned char __sdcc_iflags; \
__sdcc_iflags = (INTCON & 0xC0); \
INTCON &= ~0xC0; \
do { CODE; } while (0); \
INTCON |= __sdcc_iflags; \
} while(0)
void stdio_init() {
usart_open(USART_TX_INT_OFF & //
USART_RX_INT_ON & //
USART_BRGH_LOW & //
USART_ASYNCH_MODE & //
USART_EIGHT_BIT, //
77 // = SPBRG, 9600 baud @ 48 MHz CPU clock
);
stdout = STREAM_USART;
}
#pragma nooverlay
volatile unsigned char flag = 0;
void usartirq() interrupt 1
{
if (usart_drdy()) {
unsigned char t;
flag = usart_getc();
if (flag != 0x55) {
if (LED_PIN==0)
LED_PIN=1;
else
LED_PIN = 0;
}
}
}
void main() {
int i;
OSCCON = 0x70;
LED_TRIS = 0;
INTCON = 0;
INTCONbits.GIE = 1; // Enable all interrupts.
INTCONbits.PEIE = 1; // Enable peripheral interrupts.
stdio_init();
while (1) {
unsigned char t;
CRITICAL (t=flag; flag=0);
if (t)
usart_putc(t);
}
}
________________________________________
From: Kustaa Nyholm [kustaa.nyh...@planmeca.com]
Sent: Sunday, February 22, 2009 9:28 PM
To: sdcc-user@lists.sourceforge.net
Subject: [Sdcc-user] PIC18F4550 USART problems
Hi,
I'm having problems with PIC18F4550 USART. I'm using the usart.h routines, with
interrupts enabled for receiving.
I've got a PC that sends group of three bytes (0x55) through a serial port at
9600 baud with no pause between bytes and 100 msec between groups.
I have an *low* priority interrupt in the PIC that receives bytes from the
USART and toggles on output if the byte received is not 0x55. No other
interrupts are running/enabled. I'm observing the output with an oscilloscope.
The output never toggles, unless I deliberately send wrong characters. As
expected.
This works at different baudrates and with different delays between chars and
groups. As expected.
If I enable my main program loop the problems start. The main loop just checks
if a character is received and sends out a char through the USART. Sending is
not interrupt driven.
Observing the output pin and the PIC USART RX pin I see consistently that after
reception of two character (from PC to PIC) the output sometimes toggles.
Sometimes it also toggles after the third char. This does not happen all the
time but intermittently like once or twice a second. It never toggles after the
first character in the group. So the problem happens at about the same time the
first character that PIC main program sends completes.
If I add a 1 ms (about one char time) between chars sent from the PC , the
problem mostly, but not totally, goes away. If I add 5 ms between chars the
problem disappears.
Changing my receive interrupt to toggle every time a character is sent I see
that sometimes interrupts are missing.
I've googled a bit and looked the chip errata but not found anything special,
USART and interrupts in PIC seem rather straightforward.
I'll try to come up with a very small self contained test case, but meanwhile
I'd like to know if there are know issues or things I should/could check.
br Kusti
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------------------------------------------------------------------------------
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-OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise
-Strategies to boost innovation and cut costs with open source participation
-Receive a $600 discount off the registration fee with the source code: SFAD
http://p.sf.net/sfu/XcvMzF8H
_______________________________________________
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Sdcc-user@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/sdcc-user
