asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| AD9850 Serial driver with divisor calculation function |
 Posted: Wed Jan 04, 2012 10:39 am |
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Edited with code addition for VERY fast 18f pic master clock >24mhz 3/2016
| Code: |
// AD9850 notes: be sure to ground reset pin
// and set Data 0,1,2 per MFG data
// using fastio for the pic pins is critical
// to achieve full performance
#define Dlatch pin_B0
#define Dclock pin_C3
#define Ddata pin_C5
#define DCtog output_low(Dclock);delay_us(4);output_high(Dclock)
#define DLtog output_high(Dlatch);delay_us(4);output_low(Dlatch)
//
// do this ONCE after power on
// init the ad9850 with worst case PLL'd PIC
// 4 us delay not required on pics running at less than 20 mhz w/o PLL
void ad9850_init(void){
output_low(Ddata); // MUST be low to init
delay_us(4); // added 2016 for PIC18 Fosc>6mhz
DCtog;
DLtog;
}
// do I/O to send freq divisor to the ad9850 with zero relative phase
// execution time = 150 usec with 16 mhz PIC clock
//
void ad9850_setfreq(unsigned int32 infr){
unsigned int8 i=0; unsigned int32 D=0;
#bit curbit=D.0
D=infr; i=0;
do{ // send 4 bytes of 32 bit integer,in anti_spi order
if(curbit) output_high(Ddata );
else output_low(Ddata );
output_high(Dclock); // raise LATCH pin
D >>=1;
output_low(Dclock); // lower LATCH
}while(++i<32);
// this last byte is the 3 control bits and 5 phase bits
// defaulting to 0 relative phase for the update
i=0; output_low(Ddata); // clock out 5th control byte=0;
do{
output_high(Dclock); // raise lower LATCH cmd
i++;
output_low(Dclock);
}while(i<8);
DLtog; // set data in DDS chip
}
// calculates DDS divisor for a 125 mhz DDS clock HOWEVER ---
// NOTE: this approach LIMITS the useful max freq to less than 12 mhz
// but has 1 hz resolution
// infreq is the frequency in HZ you want generate the divisor for
//
unsigned int32 adc_makedivisor(unsigned int32 Infreq){ // infreq in hz
return ((34*infreq)+((361*infreq)/1000));
}
// full 40 mhz version- HOWEVER --- has less resolution
//
unsigned int32 adc_makedivisorH(unsigned int32 Infreq){ // infreq in hz
return ((34*infreq)+((36*infreq)/100));
}
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