> I noticed Peter Moreton mentioned having a Lassen SQ connected to a
> PIC18F452.

> Peter if you're still on the list:  Can you tell me what you did to =
get=20
> them
> talking?

> Thanks,

> -matt redmond

Matt,

I spent some time looking thru my backups tonight, but cannot find a
schematic for the PIC / Lassen SQ circuit I described. I reworked the =
design
for an Atmel ATmega128, and seemingly through away the PIC version of =
the
schematic. However, there is some C18 source code from this project =
which I
include below, which *might* be useful. From the code, I can see that I
actually used the USART to talk to the Lassen SQ. If this code is =
useful, I
can bundle up all the source including headers and email it directly to =
you.

Peter Moreton


/*
 * R700 Vehicle Telemetry Recorder
 * Author : Peter Moreton=09
 * Revision 1.0 11 June 2003
 *
 * Design notes:
 * The PIC18F452 is clocked as 16Mhz, giving 4 MIPS instruction rate.=20
 * RS232 Comms at 1200 to 76.8 Kbaud can be implemented at this clock=20
 * rate with a baud rate accuracy of 0.16%. The 16Mhz clock is used
 * to generate the High Resolution Timebases needed for CCP etc. The
 * High Accuracy Timebase is generated from a 7.5ppm 32.768 khz xtal=20
 * on Timer1, producing a clock which can be disciplined by GPS.
 *=20
 */

#include <p18cxxx.h>
#include <stdlib.h>
#include <timers.h>
#include <delays.h>
#include <usart.h>
#include <string.h>
#include "LEDMatrix.h"

#define TRUE 1
#define FALSE 0
#define DLE 0x10
#define ETX 0x3

// Global variables used primarily to get data from interrupt service
routines=20
static unsigned long julian =3D 0;

// Setup Interrupt Service Routines for low & high priority interrupts

void low_priority_isr (void);
void high_priority_isr (void);

#pragma code low_vector=3D0x18
void low_interrupt (void)
{
  // Inline assembly that will jump to the low priority ISR.
  _asm GOTO low_priority_isr _endasm
}
#pragma code                                                    // Reset to
the default code section.

#pragma code high_vector=3D0x08
void high_interrupt (void)
{
  // Inline assembly that will jump to the high priority ISR.
  _asm GOTO high_priority_isr _endasm
}
#pragma code                                                    // Reset to
the default code section.

#pragma interruptlow low_priority_isr save=3DPROD
void low_priority_isr (void)
{
        char GPSChar, GPSUTC[10];
        int GPSStrPtr;
        static char GPSStr[128];

        if (PIR1bits.RCIF=3D=3D1)                               // USART RX flag
tripped?
        {
                // TSIP packet format is: DLE pkt-id data-bytes DLE ETX

                PIR1bits.RCIF=3D0;                              // Reset the
flag
                GPSChar =3D ReadUSART();                        // Get the character
                if (GPSChar =3D=3D ETX)                         // End of
TSIP packet
                {
                                GPSUTC[0]=3DGPSStr[7];
// Copy HHMMSS to HH:MM:SS
                                GPSUTC[1]=3DGPSStr[8];
                                GPSUTC[2]=3D':';
                                        GPSUTC[3]=3DGPSStr[9];
                                        GPSUTC[4]=3DGPSStr[10];
                                        GPSUTC[5]=3D':';
                                        GPSUTC[6]=3DGPSStr[11];
                                        GPSUTC[7]=3DGPSStr[12];
                                        GPSUTC[8]=3D'\0';=09

                                PutSMatrix(GPSUTC, 0);
                        }
                        GPSStrPtr=3D0;
                }
                else
                {
                        GPSStr[GPSStrPtr++] =3D GPSChar;
                        if (GPSStrPtr =3D=3D 128)               // About to write
over end of buffer?
                                GPSStrPtr =3D 0;                        //=20
                }

                if ((PORTC & 0x8) =3D=3D 0)                     // Port RC4 =3D RS232
data RX
                        PORTC|=3D0x8;           =09
                else
                        PORTC&=3D0xF7;
        }
}

#pragma interrupt high_priority_isr save=3DPROD
void high_priority_isr (void)
{
        if (PIR1bits.TMR1IF=3D=3D1)                             // High-accuracy
timebase, TIMER1 has overflowed
        {
                PIR1bits.TMR1IF=3D0;                            // Reset the
TIMER1 overflow interrupt flag=20
                TMR1H =3D 0x80;                                 // Set
Timer1 to 0x8000 + elapsed time

                // Compute UTC timebase
                julian++;

        }
}

// End of interrupt processing code=20

void main (void)
{
        int count, i=3D0;
        unsigned long julianx=3D0;
        unsigned char opcode;

=09
        // '1' bit is input, '0' bit is output
        TRISA =3D 0b11111111;                                           //
Port A is presently unused. Set to all inputs
        TRISB =3D 0b11100000;                                           //
RB0,1,2 used by LED Matrix
        TRISC =3D 0b11000011;                                           //
RC0,1 used by 32khz osc, RC6,7 used by RS232

        // Issue startup msg to LED matrix display
//      OpenMatrix();
        PutBMatrix(MATRIX_LAMPTEST);
        Delay10KTCYx(0);
        PutBMatrix(MATRIX_CLEAR);
        PutBMatrix(MATRIX_BRIGHT_40);                   // 40%
        PutRSMatrix("TELEMETRY ", 0);
        Delay10KTCYx(0);
        PutRSMatrix("FW REV 1.1", 0);
        Delay10KTCYx(0);
        PutRSMatrix("INIT OK   ", 0);
        Delay10KTCYx(0);

        // Enable the TMR1 interrupt, setting up the timer as an external
32.768 khz, 16-bit clock
 =20
        OpenTimer1 (TIMER_INT_ON & T1_PS_1_1 & T1_OSC1EN_ON & T1_8BIT_RW);
        TMR1H =3D 0x80;                                                 //
Set Timer1 to 0x8000 (=3D dec 32768) + elapsed time (1 second)

        RCONbits.IPEN =3D 1;                                            //
Enable prioritized interrupts
        IPR1bits.TMR1IP =3D 1;                                  // Timer1
overflow is high priority
        IPR1bits.RCIP =3D 0;                                            //
USART receive is low priority
        INTCONbits.GIE =3D 1;                                           //
Enable global interrupts
        INTCONbits.PEIE =3D 1;                                  // Enable
peripheral interrupts

        // Open USART with SPBRG of 25 =3D 9600 baud @ 16Mhz xtal. Comms are
9600 baud, 8, odd, 1
        OpenUSART(              USART_TX_INT_OFF        &
                                        USART_RX_INT_ON         &
                                        USART_ASYNCH_MODE       &
                                        USART_EIGHT_BIT         &
                                        USART_CONT_RX           &
                                        USART_BRGH_LOW,
                                        25);


        while (1)
// Main routine; do this forever
        {
                if (julianx !=3D julian)                                // Time
changed ?
                {
                        julianx =3D julian;
                =09
                        if ((PORTC & 0x4) =3D=3D 0)                     // Port RC3
=3D 1PPS signal. Ultrabright LED beacon.
                                PORTC|=3D0x4;           =09
                        else
                                PORTC&=3D0xFB;

                }


        }

}

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