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SPI communication for PIC18f46

 
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sani



Joined: 24 Nov 2010
Posts: 1

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SPI communication for PIC18f46
PostPosted: Wed Nov 24, 2010 8:59 am     Reply with quote
Hi all,

I'm currently working on two PIC18f46k20 and to get two of them connected using SPI master/slave method. I'm using the MPLab compiler and built with the example code from the website but it doesn't seem to work. There is something to do the the '#fuses' definition. Can anyone tell me how to get it sorted. Appreciate it alot, thanks.

Here is the code for the master.

Code:

#include <18f4520.h>
#fuses EC,NOLVP,NOWDT,NOPROTECT
#device ADC=8
#use delay(clock=40000000)

//These define the different SPI modes in terms of constants the compiler knows about
//NOTE: our PICs only seemed to work in modes 1 and 3, though they are supposed to work with any modes
#define SPI_MODE_0 (SPI_L_TO_H | SPI_XMIT_L_TO_H)
#define SPI_MODE_1 (SPI_L_TO_H)
#define SPI_MODE_2 (SPI_H_TO_L)
#define SPI_MODE_3 (SPI_H_TO_L | SPI_XMIT_L_TO_H)

#define SS_PIN PIN_D0         //this can be any output pin on the master

void main()
{
   int val;

   //Set up the ADC to read from A0
   setup_adc_ports(AN0);
   setup_adc(ADC_CLOCK_INTERNAL);
   set_adc_channel(0);

   //The next statement sets up the SPI hardware, with this PIC as a master using mode 1
   //SPI_CLK_DIV_64 sets the speed of the SPI clock pulses--this is the slowest speed
   setup_spi(SPI_MASTER | SPI_MODE_1 | SPI_CLK_DIV_64);
   
   while(true) {
       val = read_adc();      //read the value to be sent
       
       output_low(SS_PIN);    //pull the slave select line low to select the slave
       delay_us(10);          //give the slave time to notice this (may be unnecessary)
       
       spi_write(val);        //send the value
       
       delay_us(10);          //(may be unnecessary)
       output_high(SS_PIN);   //deselect the slave.
       
       delay_ms(10);
   }
}
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Nov 24, 2010 12:39 pm     Reply with quote
Quote:
#include <18f4520.h>
#fuses INTRC_IO,NOLVP,NOWDT,NOPROTECT
#device ADC=8
#use delay(clock=4000000)

The changes shown in bold above will allow the PIC to run.
The oscillator is changed to Internal, and the clock is changed to 4 MHz.
Make both those changes, re-compile, and then you can start to test
the program.
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