AD9833 DDS: Update

Hello everyone,

Good news on the AD9833 DDS work from our R&D Lab.

FLASHBACK: Previously we could load the desired frequency using the PIC16F84A and display it on the Oscilloscope. (Refer to our previous post)

HOT NEWS: Now we can vary the frequency up and down. We have upgraded the Micro-controller to 16F628A as the migration is very simple. So how did we do it??? Refer to the code sample below and its very easy to figure it out. In case of any doubts, you can always leave a comment with your email or you can email us.

Also, suggestions and feedback are most welcome.

Circuit Explanation: We have used RA1 and RA2 as the up and down inputs. PORTB is used to feed the signals to the AD9833. Circuit diagram will be uploaded soon.

ASM code: Click Here

Code:

"

list      p=16F628A            

#include <P16F628a.inc>  

__CONFIG       _PWRTE_ON & _XT_OSC & _WDT_OFF & _MCLRE_ON & _LVP_OFF & _BODEN_OFF & _CP_OFF

temp1 equ    028H

cnt equ 02AH

count1 equ 02BH

count2 equ 02CH

count3 equ 02DH

LSBreg1 equ 032H

LSBreg2 equ 033H

MSBreg1 equ 034H

MSBreg2 equ 035H

ORG     0x00 ; processor reset vector

 

movlw 07h 

movwf CMCON

  bsf STATUS,RP0

movlw b'11111111' ; RA0..RA7 inputs

movwf   TRISA

          movlw b'00000000' ; RB0..RB7 outputs

movwf   TRISB

bcf STATUS,RP0

movlw 0x7F

movwf LSBreg1

movlw 0x00

movwf LSBreg2

movlw 0x4F

movwf MSBreg1

movlw 0x0F

movwf MSBreg2

call main1

main2 call Delay

btfss PORTA,1

call inmsb

btfss PORTA,2

call demsb

goto main2

inmsb incf MSBreg2,1

call main1

return

demsb decf MSBreg2,1

call main1

return

write1

movlw 8

movwf cnt

send_loop

bcf PORTB,4 ; assume zero bit, AD9832 SDATA pin = 0

btfsc temp1,7 ; check MSBit of 8-bit word

bsf PORTB,4

nop

bcf PORTB,5

nop ; make a pulse on AD9833 SCLK pin

bsf PORTB,5

; rotate all 8 bits left (through carry)

rlf temp1,f

decfsz cnt,f

goto send_loop

return

Delay movlw 0x11

movwf count1

movlw 0x5D

movwf count2

movlw 0x05

movwf count3

Delay_0 decfsz count1,f

goto $+2

decfsz count2,f

goto $+2

decfsz count3,f

goto Delay_0

return

main1 bcf PORTB,6

movlw 0x21

movwf temp1

call write1

movlw 0x00

movwf temp1

call write1

clrf temp1

movf LSBreg1,0

movwf temp1

call write1

movf LSBreg2,0

movwf temp1

call write1

movf MSBreg1,0

movwf temp1

call write1

movf MSBreg2,0

movwf temp1

call write1

movlw 0xC0

movwf temp1

call write1

movlw 0x00

movwf temp1

call write1

movlw 0x20

movwf temp1

call write1

movlw 0x00

movwf temp1

call write1

bsf PORTB,6

return

end

"