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PCD: Changing SPI Clock with #use SPI

 
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dneale



Joined: 25 Nov 2009
Posts: 9
Location: Albuquerque NM

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PCD: Changing SPI Clock with #use SPI
PostPosted: Tue Mar 09, 2010 4:24 pm     Reply with quote
Hi,

I am interfacing an AD7367 ADC to a 24FJ128GA006. I have the code working but I'm getting way too much noise. Its on a breadboard so that is some of it but I want to check if some of it is in the SPI sampling so I need to slow the clock since #use SPI sets the fastest clock. I cannot seem to get the SPICON1 clock bits to change.

I'm running PCD & IDE version 4.105 with a CCS PIC 24 Demo board.

Thanks for your help.

Dave

Code:
#include "C:\Program Files\PICC\24F Exercises\A2D Test7.h"
#include <stdio.h>

#use rs232(UART1, DEBUGGER)
#use spi(SPI1, MASTER, MODE=3, BITS=32, STREAM=A2D_Data)
#use fast_io(D)

//SPI chip select and conversion start pins
#define AD7367_nCS PIN_D0
#define AD7367_nCNVST PIN_D1

#bit SPI_EN = 240.15
#bit SPI_DIV_64 = 242.0
#bit SPI_DIV_16 = 242.1


/* Print n as a binary number */
void printbitssimple(int n) {
    unsigned int i;
    i = 1<<(sizeof(n) * 8 - 1);

    while (i > 0) {
        if (n & i)
            printf("1");
        else
            printf("0");
        i >>= 1;
    }
}

void main()
{
   
    int32 A2D_Result;
    int16 ADC_A_RES, ADC_B_RES, Dummy;
    int8  k=0,n=11;
   
    set_tris_D(0x00);
     
    SPI_EN = 0;
    SPI_DIV_64 = 0;
    SPI_DIV_16 = 0;
    SPI_EN = 1;
   
    while(k < n )
    {
   
    output_low(AD7367_nCNVST);//Pulse to conversion start
    output_high(AD7367_nCNVST);
       
    output_low(AD7367_nCS);//Enable the data line of the A2D
           
    ADC_A_RES = spi_xfer(A2D_Data,Dummy,16);//read the results
   
    ADC_A_RES = ADC_A_RES>>2;
 

    ADC_B_RES = spi_xfer(A2D_Data,Dummy,16);
           
    ADC_B_RES = shift_right(&ADC_B_RES,2,0);
    ADC_B_RES = shift_right(&ADC_B_RES,2,0);
     
    output_high(AD7367_nCS);//Tristate the data line

    printbitssimple(ADC_A_RES);
    printf("\n\r");
   
    delay_ms(1);
   
    k++;
    }//end while

}


A2D Test7.h
Code:
#include<24FJ128GA006.h>

#FUSES NOWDT                     //No Watch Dog Timer
#FUSES NOJTAG                    //JTAG disabled
#FUSES NOPROTECT                 //Code not protected from reading
#FUSES NOWRT                     //Program memory not write protected
#FUSES NODEBUG                   //No Debug mode for ICD
#FUSES ICSP2                     //ICD uses PGC2/PGD2 pins
#FUSES NOWINDIS                  //Watch Dog Timer in Window mode
#FUSES WPRES128                  //Watch Dog Timer PreScalar 1:128
#FUSES WPOSTS16                  //Watch Dog Timer PostScalar 1:32768
#FUSES NOIESO                    //Internal External Switch Over mode disabled
#FUSES FRC_PS                    //Fast RC Oscillator with Post Scaler
#FUSES NOCKSFSM                  //Clock Switching is disabled, fail Safe clock monitor is disabled
#FUSES NOOSCIO                   //OSC2 is clock output
#FUSES NOPR                      //Pimary oscillaotr disabled


#device ICD=TRUE
#fuses HS,PR
#use DELAY (CLOCK=20000000)

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Dave N
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Tue Mar 09, 2010 8:19 pm     Reply with quote
According to the PCD manual, you can use the BAUD parameter in your
#use spi() statement to set the SCLK speed:
Quote:

#USE SPI

Syntax: #use spi (options)

BAUD=n Target bits per second. Default is as fast as possible.


Add the parameter shown in bold below. Fill in the desired baud rate.
Quote:

#use spi(SPI1, MASTER, MODE=3, BITS=32, BAUD=xxxxx, STREAM=A2D_Data)

The compiler will try to get as close as possible to your desired baud
rate, based on the limitations of the SPI module's baud rate generator.
dneale



Joined: 25 Nov 2009
Posts: 9
Location: Albuquerque NM

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PostPosted: Wed Mar 10, 2010 5:27 pm     Reply with quote
Thanks so much. My Nov 2009 manual strikes doesn't have that option. I see there is a newer one. I'll have to download it.

Thanks.

Dave
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Dave N
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