CCS :: View topic

FAQ

Forum Help

Official CCS Support

Profile Log in to check your private messages Log in

CCS does not monitor this forum on a regular basis.

Please do not post bug reports on this forum. Send them to CCS Technical Support

SPI comm

CCS Forum Index -> General CCS C Discussion

View previous topic :: View next topic

Author

Message

rfjhh

Joined: 31 Mar 2011
Posts: 51
Location: Mexico

SPI comm

Posted: Thu Jun 15, 2017 9:05 am

I'm new in SPI comms. I need to communicate two PICs:
16F887 Master
16F886 Slave

I've written the following two programs:

MASTER:

Code:

#include<16f887.h>
#use delay (clock = 20 MHz)
#include<LCD.c>
#fuses HS, NOWDT, NOMCLR, NOBROWNOUT, NOLVP, NOPROTECT, NOFCMEN, NODEBUG
#use fast_io(E)
#use standard_io(C)
#use standard_io(A)

void main()
{
int8 valor;
lcd_init();
setup_spi(SPI_MASTER | SPI_H_TO_L | SPI_CLK_DIV_16);
lcd_gotoxy(1,1);
printf(lcd_putc, "SPI maestro");
while(true)
{
   output_bit(PIN_B0, 1);    // SS
   lcd_gotoxy(1,2);
   printf(lcd_putc, "Recibiendo");
   valor=spi_read();
   delay_ms(2);
   lcd_gotoxy(1,2);
   printf(lcd_putc, "Valor = %u", valor);
   output_bit(PIN_B0, 0);
   delay_ms(1000);
}
}

SLAVE

Code:

#include<16f886.h>
#use delay (clock = 8 MHz)
#include<LCD.c>
#fuses INTRC_IO, NOWDT, NOMCLR, NOBROWNOUT, NOLVP, NOPROTECT, NOFCMEN, NODEBUG
#use fast_io(E)
#use standard_io(C)
#use standard_io(A)
/* RC3 SPI CLK
RC4 SPI SDI
RC5 SPI SDO
RC0 SPI SS
*/

void main()
{
int8 valor;
lcd_init();
setup_spi(SPI_SLAVE | SPI_H_TO_L);
lcd_gotoxy(1,1);
printf(lcd_putc, "SPI esclavo");
setup_oscillator(OSC_8MHZ);
while(true)
{
   if(input(PIN_C0)==1)    // entrada SS
   {
      lcd_gotoxy(1,2);
      printf(lcd_putc, "Enviando");
      spi_write(input_b());
   }
   lcd_gotoxy(1,2);
   printf(lcd_putc, "Terminado");
}
}

But I have nothing in SCK, SDO, SDI.
May somebody help me?

Regards
Ricardo

alan

Joined: 12 Nov 2012
Posts: 357
Location: South Africa

Posted: Thu Jun 15, 2017 9:12 am

If you read the manual your use of spi_read are wrong for master.

Quote:

Return a value read by the SPI. If a value is passed to the spi_read() the data will be clocked out and the data received will be returned. If no data is ready, spi_read() will wait for the data is a SLAVE or return the last DATA clocked in from spi_write().

If this device is the MASTER then either do a spi_write(data) followed by a spi_read() or do a spi_read(data). These both do the same thing and will generate a clock. If there is no data to send just do a spi_read(0) to get the clock.

rfjhh

Joined: 31 Mar 2011
Posts: 51
Location: Mexico

Posted: Thu Jun 15, 2017 10:11 pm

I've modified the code as follows:
MASTER

Code:

#include<16f887.h>
#use delay (clock = 20 MHz)
#include<LCD.c>
#fuses HS, NOWDT, NOMCLR, NOBROWNOUT, NOLVP, NOPROTECT, NOFCMEN, NODEBUG

#use fast_io(E)
#use standard_io(C)
#use standard_io(A)

void main()
{
int8 valor;
set_tris_e(0xfe);
lcd_init();
setup_spi(SPI_MASTER | SPI_H_TO_L | SPI_CLK_DIV_16);
lcd_gotoxy(1,1);
printf(lcd_putc, "SPI maestro");
while(true)
{
   lcd_gotoxy(1,2);
   printf(lcd_putc, "Recibiendo");
   output_high(PIN_E0);    // SS
   valor=spi_read(0x96);
   delay_ms(2);
   lcd_gotoxy(1,2);
   printf(lcd_putc, "Valor = %u", valor);
   output_low(PIN_E0);
   delay_ms(100);
}
}

SLAVE:

Code:

#include<16f886.h>
#use delay (clock = 8 MHz)
#include<LCD.c>
#fuses INTRC_IO, NOWDT, NOMCLR, NOBROWNOUT, NOLVP, NOPROTECT, NOFCMEN, NODEBUG

#use fast_io(B)
#use fast_io(C)
#use standard_io(A)
/* RC3 SPI CLK
RC4 SPI SDI
RC5 SPI SDO
RC0 SPI SS
*/

void main()
{
int8 valor;
set_tris_b(0xff);
set_tris_c(0xdf);
setup_spi(SPI_SLAVE | SPI_H_TO_L | SPI_CLK_DIV_16);
setup_oscillator(OSC_8MHZ);
while(true)
{
   valor = input_b();
   if(input(PIN_C0)==1)    // entrada SS
   {
      spi_write(valor);
   }
}
}

Now I have the clock signal, but nothing happens from the slave to the master.

Display posts from previous:

	CCS Forum Index -> General CCS C Discussion	All times are GMT - 6 Hours
Page 1 of 1

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum