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AD9833

 
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Milhaus



Joined: 20 Oct 2007
Posts: 9

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AD9833
PostPosted: Fri Dec 07, 2007 5:07 am     Reply with quote

Hi all,
i am looking for driver for DDS chip AD9833.
Can you help me ?

Milos
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Sun Dec 09, 2007 4:14 pm     Reply with quote

This AD9833 project has code that could be translated to CCS;
http://johnryder.wordpress.com/2007/03/26/dds-frequancy-generator/
Guest








PostPosted: Sun Jan 20, 2008 1:02 pm     Reply with quote

I have written following library:

[deleted]

This does work, but the frequency dont change after calling following SetDDSFrequency functions. Please could you help me ?

Thanks
Milos
Milhaus



Joined: 20 Oct 2007
Posts: 9

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PostPosted: Sun Jan 20, 2008 1:07 pm     Reply with quote

I have written following library:
Please ignore previous post. It is not displayed correctly.
Code:

// AD9833 definitions
#define   FREQ0      0x4000      // Select FREQ0 register
#define   FREQ1      0x8000      // select FREQ1 register
#define   PHASE0      0xC000      // select PHASE0 register
#define   PHASE1      0xE000      // select PHASE1 register

// Control register bits
#define   B28          (1<<13)
#define   HLB          (1<<12)
#define   FSELECT      (1<<11)
#define   PSELECT      (1<<10)
#define   ADRESET      (1<<8)
#define   SLEEP1       (1<<7)
#define   SLEEP12      (1<<6)
#define   OPBITEN      (1<<5)
#define   DIV2         (1<<3)
#define   ADMODE       (1)


// Func prototypes
void AD9833_Write(unsigned int16 value);
void SetDDSFrequency(float Freq);
void AD9833_reset();


void AD9833_Write(unsigned int16 value)
{
int8 clsb, cmsb;

clsb = (int8)value;
cmsb = value >> 8;
output_low(FSYNC);
delay_us(5);
spi_write(cmsb);
spi_write(clsb);
delay_us(5);
output_high (FSYNC);
}

void AD9833_reset()
{

 AD9833_Write(B28|ADRESET|OPBITEN|DIV2); //reset
 AD9833_Write(B28|OPBITEN|DIV2); // square wave

}


void SetDDSFrequency(float Freq)
{
unsigned long i,lsb,msb;

   Freq = Freq / 0.093132258;     // for 25Mhz osc
   i = (unsigned long)Freq;
   lsb = (i & 0x3fff) + FREQ0;
   msb = ((i>>14) & 0x3fff) + FREQ0;
   AD9833_Write(lsb);
   AD9833_Write(msb);
}


In my main code i have:
Code:

#include <16F819.h>
#device PASS_STRINGS = IN_RAM
#fuses NOWDT, INTRC_IO, NOPROTECT,NOBROWNOUT,NOMCLR,NODEBUG
#use delay(clock=8M)

#use fast_io(a)
#use fast_io(b)
void main (){
int32 i;
SET_TRIS_B(195);
SET_TRIS_A(255);

setup_spi(SPI_MASTER | SPI_L_TO_H | SPI_XMIT_L_TO_H |SPI_SS_DISABLED | SPI_CLK_DIV_4 );
AD9833_reset();
SetDDSFrequency(10000);
delay_ms(2000);
SetDDSFrequency(2000);
delay_ms(2000);
SetDDSFrequency(4000);
delay_ms(2000);
SetDDSFrequency(500);
delay_ms(2000);
}


This does work, but the frequency dont change after calling following SetDDSFrequency functions. Please could you help me ?

Thanks
Milos
marcoscab1166



Joined: 19 May 2019
Posts: 6

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PostPosted: Thu Jan 02, 2020 8:33 am     Reply with quote

Anonymous wrote:
I have written following library:

[deleted]

This does work, but the frequency dont change after calling following SetDDSFrequency functions. Please could you help me ?

Thanks
Milos


Hello there. You're not using the #use SPI line
In that line you define the pins and the way of function of the SPI.
Without it, doesn't matter if you configure it with setup_spi
Ttelmah



Joined: 11 Mar 2010
Posts: 19195

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PostPosted: Fri Jan 03, 2020 9:40 am     Reply with quote

Er. Sorry, but wrong.

The 'older' CCS way of setting up SPI, is setup_spi. This is used with
the spi_read and spi_write functions. Only works with the hardware ports.

The 'newer' way is #USE SPI, with the spi_xfer functions. This supports
both hardware and software SPI.

What is posted is perfectly acceptable and sets up the SPI with the
setup_spi line. However as posted it'll only work with the hardware SPI1
port.

An issue though is using the 'unsigned long' designation. On a PIC16,
unsigned long is only a 16bit variable. It is much safer and better in general
to be explicit and use lengths like unsigned int32.
Now since this is a 16bit variable, this line:

msb = ((i>>14) & 0x3fff) + FREQ0;

can only return the upper 2 bits of 'i'.

Also the values given by the division are always overflowing the integer.

So 10000/0.093132258 = 107374 which won't fit in a 16bit integer.....

Then you are generating 16bit results and putting these into variables
called lsb and msb, and writing just the low 8bits of these.
Understand spi_write writes a _byte_ only.

So:
Code:

#define   FREQ0      0x4000    // Select FREQ0 register
void AD9833_Write(unsigned int16 value)
{
   int8 clsb, cmsb, dummy;

   clsb = make8(value,0); //faster than rotations etc..
   cmsb = make8(value,1);
   output_low(FSYNC);
   delay_us(1);
   dummy=spi_read(cmsb);
   dummy=spi_read(clsb); //Using read forces the transfer to complete
   //before returning. Removes the need for delays
   output_high (FSYNC);
}

void SetDDSFrequency(float Freq)
{
   unsigned int32 i, lsw, msw;

   i = Freq * 10.737418;     // for 25Mhz osc
   //Multiplication is always faster than division.

   lsw= (i & 0x3FFF) | FREQ0; //low 14 bits
   msw = (i & 0xFFFC000) >>14; //Upper 14 bits
   msw |= FREQ0;
   AD9833_write(0x2000); //Control word write
   AD9833_Write(lsw); //Low 14 bits
   AD9833_Write(msw); //High 14 bits
}
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