Calculate tuning value for the AD9850 DDS.

[tasmod]

Very interesting Henrik.

I have only skimped through the wiki just now and will read properly offline.

I'm currently using one of the cheap ebay modules on a board i designed and a 16f628 to produce a tunable signal generator dds, this is other peoples code in asm though. One other code is a sweep generator/signal generator with decade digit selection by rotary encoder.

I had been trying to do the maths (Nowhere near my capability) to use a rotary encoder in pbp. I did achieve an incrementing counter in pbp with it but got no further to convert to the tuning word.
I was also able to get it to any frequency by inserting the byte sequence for the tuning word into the code. I had all the amateur bands set up as subs and using a pushbutton could step through them.

I wanted to do the dds in pbp so I could add further features such as keypad freq entry, vfo a and vfo b, along with band switching outputs for a ham radio transceiver I'm building.

Below is some sample code. I did move on much further but then got into a jam with ideas.

Regards,
Rob

'****************************************************************
'*  Name    : DDS Frequency Generator                           *
'*  Author  :                                    *                               *
'*  Date    : 10/29/2012                                        *
'*  Version : 1.0                                               *
'*  Notes   : Uses ebay DDS board and rotary encoder            *
'*          :                                                   *
'****************************************************************

'
;  16f628a
;  __config _CP_OFF&_LVP_OFF&_BODEN_OFF&_PWRTE_OFF&_WDT_OFF&_INTRC_OSC_NOCLKOUT
; 
'       
'
        '
        '       LCD Display
        '       -----------
        '      
        '
Define LCD_DREG PORTB          ' Port for LCD Data
Define LCD_DBIT 0              ' Use lower 4 bits of Port
Define LCD_RSREG PORTB         ' Port for RegisterSelect (RS) bit
Define LCD_RSBIT 6             ' Port Pin for RS bit
Define LCD_RWBIT 5             ' Port Pin for RS bit
Define LCD_EREG PORTB          ' Port for Enable (E) bit
Define LCD_EBIT 4              ' Port Pin for E bit
Define LCB_BITS 4              ' Using 4-bit bus
Define LCD_LINES 2             ' Using 2 line Display
Define LCD_COMMANDUS 1200      ' Command Delay (uS)
DEFINE LCD_DATAUS 50           ' Data Delay (uS)
        '
        '      Control Buttons/Lines
        '      ---------------------
PB_1 var PortA.4              ' Take this pin low momentarily to change step
PB_2 var PortA.3              ' Take this pin low momentarily to change band
PB_3 var PortA.2              ' Take this pin low momentarily to RESET
EncoderRight var PortA.1       ' rotary encoder pin
EncoderLeft var PortA.0      ' rotary encoder pin


ddsload var PortB.7           ' dds control word pin
ddsdata var PortB.3           ' dds data input
ddsclock var PortB.2          ' dds clock input



fStep var byte
fcount var byte
Counter var word


    CMCON=7      'sets 16f628 comparator pins to digital
    TRISA=%00011111       'Button & encoder inputs

Counter = 0
fcount = 0
fstep = 1     ;start at 1 digit count

    LOW DDSLOAD

'CONFIGURE DISPLAY
    pause 1000
    LCDOUT $FE,1    ' Clear screen
    pause 10
    lcdout $fe,$c0,dec5 counter        ; reset to zero on start


ddstart:
    shiftout ddsdata,ddsclock,0,[ $07,$2B,$02,$0C ]   ;start value
    toggle ddsload
    pause 100

;Rotary Encoder Code################################################

mainloop1:

    if EncoderRight=0 then                 'here is switch 2 of the rotary encoder
        counter=counter+1
        gosub up
        gosub dds
        gosub lcd
    endif

'IF PB_1=0 THEN inc_step

    if EncoderLeft=0 then                 'here is switch 1 of the rotary encoder
        counter = counter-1
        gosub down
        gosub dds
        gosub lcd
    endif

    goto mainloop1
    
lcd:
    lcdout $fe,$c0,dec5 counter
    while (EncoderLeft=0 or EncoderRight=0):pause 10:wend
    return


inc_step:
    fcount=fcount+1
    if fcount=2 then fstep=100
    if fcount=1 then fstep=10
    fcount=1
    return

dds:
    shiftout ddsdata,ddsclock,0,[counter]
    toggle ddsload
    return

up:

    counter[0]=counter[0]+1
    if counter[0]>99 then
        counter[0]=0
        counter[1]=counter[1]+1
        if counter[1]>99 then
            counter[1]=0
            counter[2]=counter[2]+1
            if counter[2]>99 then
                counter[2]=0
                counter[3]=counter[3]+1
                if counter[3]>99 then
                    counter[3]=0     ;reset to zero
                endif
            endif
        endif
    endif
return

down:

    counter[0]=counter[0]-1
    if counter[0]<1 then
        counter[0]=0
        counter[1]=counter[1]-1
        if counter[1]<1 then
            counter[1]=99
            counter[2]=counter[2]-1
            if counter[2]<1 then
                counter[2]=99
                counter[3]=counter[3]-1
                if counter[3]<1 then
                    counter[3]=99
                endif
            endif
        endif
    endif
return

end