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SPI problem with AD DAC

 
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denkov



Joined: 19 Dec 2005
Posts: 2

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SPI problem with AD DAC
PostPosted: Thu Feb 02, 2006 2:31 pm     Reply with quote
Kenny



Joined: 07 Sep 2003
Posts: 173
Location: Australia

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PostPosted: Thu Feb 02, 2006 5:07 pm     Reply with quote
The data sheet says that this dac can be used with spi.

From the timing diagrams, the clock needs a low to high transition at
mid-bit time, and the idle state of the clock is low.
Try a test routine like the one below

Connections:
Pic spi data out to dac data in
Pic spi clock to dac clock
Pic port pin to dac latch

Code:

#include <18F452.h>
#use delay(clock=16000000)
#fuses HS,NOWDT,NOLVP,PUT,NOPROTECT,BROWNOUT

#define AD420_LATCH  PIN_D1
int16 val = 0x7fff;           // Half scale

void main(void)
{
   setup_spi(spi_master | spi_l_to_h |spi_clk_div_16);

   output_low(AD420_LATCH);
   
   spi_write(val >> 8);    // Send msb
   spi_write(val & 0xff);  // Send lsb
   
   output_high(AD420_LATCH);
   
   while(1);               // Dac output should be half full scale   
}   
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