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kagalou
Joined: 19 Jan 2012
Posts: 6
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| Transmission SPI |
 Posted: Wed Jun 06, 2012 12:54 am |
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Hi all !
I have a little problem with my SPI transmission. I have a master and a slave. I have to make a program for two. The master send a value and the slave receive.
Problem. My master send 30, and my slave in the LCD write 252. I need help. If you want, I can make my two programs.
Thanks |
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bkamen
Joined: 07 Jan 2004
Posts: 1611
Location: Central Illinois, USA
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| Posted: Wed Jun 06, 2012 1:06 am |
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Please see the second sticky message at the top of this forum. (PIC101)
Then come back and post the needed information (as listed there.)
-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D |
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kagalou
Joined: 19 Jan 2012
Posts: 6
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| Posted: Wed Jun 06, 2012 1:17 am |
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Humm. I not sure I have all understand. But I test :p
So my slave is a 18F2580. For my project I need a SPI transmission.
So I make two program's with MPLAB.
For the slave :
| Code: |
#include <18F2580.h>
#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)
#use delay (clock=4000000)
#use SPI(DI=PIN_C4, DO=PIN_C5, CLK=PIN_C3, BITS=10)
#include "LCD Picdem2.C"
int a;
#int_SSP
void SSP_isr(void)
{
while (!spi_data_is_in());
a=spi_read();
}
/*/ Partie LCD/*/
void main ()
{
int a;
enable_interrupts(INT_SSP);
enable_interrupts(GLOBAL);
lcd_init();
setup_spi (spi_slave| SPI_H_TO_L|SPI_CLK_DIV_16);
while(true)
{
lcd_gotoxy(1,1);
PRINTF(LCD_PUTC,"Env master %u",a);
}
}
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My master is a 18F4580:
| Code: |
#include <18F4580.h>
#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_A5
#use delay (clock=4000000)
#use SPI(DI=PIN_C4, DO=PIN_C5, CLK=PIN_C3, BITS=10)
#include "LCD Picdem2.C"
int a=100;
int y=0,x=0;
int16 toto;
void main(void)
{
set_tris_b(0b11111110);
setup_spi (spi_master|SPI_L_TO_H|SPI_CLK_DIV_16);
lcd_init();
/*/BOUCLE/*/
while(true)
{
output_low(SS);
spi_write(a);
delay_ms(20);
output_high(SS);
/*/ Partie LCD/*/
LCD_PUTC ("\f");
lcd_gotoxy(1,1);
PRINTF(LCD_PUTC,"Envoi %u" a);
}
}
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So. The problem is the next. My slave receive the value "a" but the master send 100 and my slave receive 252, or 171 if it want.
Have you an idea ? |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19337
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| Posted: Wed Jun 06, 2012 1:40 am |
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Several things:
First INT_SSP, occurs _because_ a character has been received. You don't want/need to test if a character is available in the ISR. Just read it.
Second, the clock edges used by master and slave, _must_ be the same You are telling the slave to use the opposite edge of the clock from the master.....
Third, setup the SPI, _before_ enabling the interrupts.
Fourth, you _must not_ specify a clock rate in the slave. It is the master that controls the clock.
Fifth, you need some sort of signal to say to the main code in the slave that a character has been received. Otherwise you will keep displaying a character even if a new one has not arrived.
Best Wishes |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Wed Jun 06, 2012 8:20 am |
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6) Do Not mix the #USE SPI and setup_spi methods! The setup_spi command is an old mechanism in the CCS compiler which has proved to be working. The #USE SPI method is newer and has many more options. Choose one method and never mix them as that will lead to errors.
7) You don't have to setup the TRIS registers, the CCS compiler will do this for you. Only in special situations where you need speed or memory optimization you should set the TRIS registers yourself, but then you also need to define #USE FAST_IO otherwise the compiler will change your settings anyway.
8) Spi_setup should be the same in the master and slave. Now they are using different spi mode configurations and that is never going to work.
9) You have SPI_MODE_x defines in your code. Nice! But you never use them so now it is only garbage code. |
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