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SPI problem (not even clock) with PIC18F452

 
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PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Sat Feb 19, 2011 1:25 pm     Reply with quote
Run a simple test program. Then look at Pin C3 for the SPI clock.
Example:
Code:

#include <18F452.h>
#fuses HS, NOWDT, PUT, BROWNOUT, NOLVP   
#use delay(clock = 20000000)   

#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)

//========================================
void main()
{

setup_spi(SPI_MASTER | SPI_MODE_0 | SPI_CLK_DIV_64);

while(1)
  {
   spi_write(0x55);
   delay_us(100);
  }

}

Don't run it in Debug mode. Don't attempt to step through the code.
Compile and run it in Release mode. You should see the SPI clock.
Nora



Joined: 23 Mar 2008
Posts: 50

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PostPosted: Sat Feb 19, 2011 1:33 pm     Reply with quote
I DO see the clock.
Thanks!
Ttelmah



Joined: 11 Mar 2010
Posts: 19506

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PostPosted: Sat Feb 19, 2011 4:17 pm     Reply with quote
And, on sending 16bits, just send two lots of 8bits. The _hardware_ only sends 8bits at a time, and if you load a new byte immediately, the transaction is effectively 'non stop' (which shouldn't matter anyway with SPI - this is why it sends a clock...).

Best Wishes
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