PIC DDS

Starting to put together code for DDS using a rotary controller. Using AD9951, PIC 16F877A, a cheap £1.09 ALPS encoder from Farnell, a 2x16LCD and a keypad £3 from Maplin.

The spec is:

1) DUAL VFO, that is VFO A, VFO B and A=B facilities.

2) UP to 50 spot frequency stored in MEMORY.

3) Three modes of operation

a) DIRECT where the frequency output has no offset displayed.

b) VFO MODE, where a frequency offset (IF) is applied VFO+IF, VFO-IF, IF-VFO).

While in this mode, VFO A or B is displayed on the top line of the LCD.

b) MEMORY MODE, where the encoder is used to select a previously saved frequency. While in this mode, MEM is displayed on the top line of the LCD.

4) KEYPAD Frequency entry and additional 7 Press buttons for other functions.

The remaining Functions included in the KEYPAD itself.

5) UP/DOWN fast search in three different steps using KEYPAD which is user selective.

6) SCAN and quick UP/DOWN search in three different steps with auto Repeat on PTT.

7) Frequencies are entered in MHz, the * is used to enter a decimal point,

and the # is used to ENTER the completed frequency.

If the first digit entered is the #, the number entered will be negative.

8) S- Meter reading from S0 to S9+40db in logarithmic db range.

9) Variable rate tuning to use cheap mechanical encoders.

10) Step size can be changed from 1Hz to MHz range.

11) RIT facility.

12) VFO copy to MEMORY and from MEMORY to any VFO (A/B) facility.

13) AM/LSB/USB/CW modes Operation with PIC pin outputs for switching.

14) Allows -Ve and +Ve IF OFFESTS. Offset frequency = any value from min RX frequency to Max 999MHz

15) 10 RX BANDPASS filter selection for RX coverage from 1.5MHz to 30MHz. Usefull to set up an All band RX.

16) BAND PASS filter switching selectivity 1Hz and 1ms switching speed, which allows cross band Operation.

17) CW OFFSET adds to TX Frequency when transmitting thus avoids modulated CW.

18) Save to MEMORY and Copy from MEMORY functions.

19) Scan VFO frequency and Scan MEMORY facility

20) Time out function for ignoring any wrong entry in system settings.

21) Auto repeat function for respective keys.

22) Display Multiplier Option to use with VHF rigs

23) Menu screen allows user to change any settings in the setup screen.

24) All settings can be changed in the SETUP screen at any time even when the DDS is in working mode including DDS chip type and Reference Clock.

25) SPLIT operation

26) CW OFFSET adds to TX Frequency when transmitting thus avoids modulated CW.

Coding PIC with MikroBasic from www.mikroe.com which creates asm which I then can compile with MPASM to HEX and burn to PIC.

Some code started out life as examples from them.

First play...to confirm can work out direction:

'PortA.0 is "A" Input
'PortA.1 is "B" Input
'"A" is direction indicator based on rising-edge of "B"; 1 = CW, 0 = CCW

dim b_old as integer
dim b_new as integer
dim counter as integer

TRISA = 000011
PORTA = 0
counter = 0

IF (PORTA AND 2) XOR b_old <> 0 THEN                'test for encoder change on "B"
   b_new = PORTA AND 2
   IF b_new > b_old THEN                            'test if "B" is rising edge
      IF (PORTA AND 1) = 1 THEN                     '"A" value is direction...1=CW, 0=CCW
         inc(counter)                               'increment counter
      ELSE
         dec(counter)                               'decrement counter
      END IF
   b_old = b_new                                    'update b_old after changes
END IF

This little example uses the 7 seg display and one of the cheap encoders from farnell...

' Declare Variables
Dim NewRead, OldRead, TempRead, i As BYTE
Dim Rotation As Boolean

' Procedure to figure out what is the rotation direction
Sub Procedure Direction(Dim Rotation As Boolean)
If Rotation = 1 Then
Inc(i)
Else
Dec(i)
End If
End Sub

Main:

' Use PortA <1,0> as the rotary encoder inputs on PIC
TRISA = 3
TRISB = 0

' Init PIC ports as you want, except for PortA <1,0> to 0
PORTA = 0
PORTB = 0

' PortA <1,0> only required
' Read rotary encoder when the PIC is first powered on
TempRead = PORTA
NewRead = TempRead And 3

While (True)

Do

' Init both byte variables for each new reading
OldRead = NewRead
' Now start reading
TempRead = PORTA ' Read the NewRead value to see if changed
NewRead = TempRead And 3
' If not changed, keep reading
Loop Until (NewRead <> OldRead)

' Xor left bit of NewRead and right bit of OldRead
Direction (NewRead.1 Xor OldRead.0)

Wend

End.

Then DDS control of AD9834 like this:

program AD9834

        dim hmsb, hlsb, lmsb, llsb as byte

        sub procedure ddswrite
        TRISC = TRISC and $FD
            Spi_Init
            ClearBit(PORTC,1)             'Sync low enable write
            Spi_Write($F8)                'Setup AD9834 for writing
            Spi_Write($00)                'Just padding.......
            Spi_Write($33)                'Write High MSB into register $33
            Spi_Write(hmsb)
            Spi_Write($22)                'Write Low MSB into register $22
            Spi_Write(hlsb)
            Spi_Write($31)                'Write High LSB into register $31
            Spi_Write(lmsb)
            Spi_Write($20)                'Write Low LSB into register $20
            Spi_Write(llsb)
            Spi_Write($C0)                'Enable AD9834 for transmit
            Spi_Write($00)'               'Just padding.......
            SetBit(PORTC,1)               'Sync high disable write
            end sub
main:
'     while true
     
        hmsb = 4
        hlsb = 0
        lmsb = 0
        llsb = 0
       
        ddswrite

'        wend
  end.

Using another routine called Print_Dec_16 which handles all the LCD figure justification and then putting it all together a starting place based on code by kuhng@vodamail.co.za and a couple others, will provide proper references, I get:

program AD9851
' Author M1KTA, dombaines@yahoo.com
' A simple program to enable Rotary Encoder control of an AD9851 DDS
' based on a simple program to enable KeyPad control of an AD9851 DDS
' DDS circuit from www.amqrp.org/kits/dds60
' Generate any frequency up to about 80 MHz, 1Hz steps ! (Specs 60 MHz)
' 16X2 Lcd on Port D, DDS on Port C, KeyPad on Port B
' Default startup values in eeprom, 1 MHz out, for 180 MHz Clock
' Standard Pic 16F877A, EasyPic4 connections apply
' RA0 switches display to frequency entry, RA1 changes clock value
' Both pins are normally pulled high, switches when pulled low
' KeyPad "*" deletes last keypress only, "#" writes new values to eeprom
' Port B KeyPad, pins pulled LOW !

        include "Print_Dec_16"      ' Xor's lcd print utility
        symbol delay50  = Delay_ms(50)
        symbol delay500 = Delay_ms(500)
        Dim frequency, xtal, cfreq, KeyInput,KeyInputOld as longint
        dim Key,Key1, byte_s as byte
        dim myvar as string[11]

        const KeyPad as byte[16] = (49, 50, 51, 65,  'Map 4*4 KeyPad to ascii
                                    52, 53, 54, 66,
                                    55, 56, 57, 67,
                                    42, 48, 35, 68)

sub procedure Welcome  ' Welcome Message
    dim I as byte
    lcd_cmd(LCD_CURSOR_OFF)
    lcd_cmd(lcd_clear)
    lcd_out(1, 4, "M1KTA")
    lcd_out(2,4,"AD-9851 DDS")
    For I = 0 to 3
    Delay500
    Next I
    lcd_cmd(lcd_clear)   ' Message Ends
end sub

' Read frequency value stored in eeprom
sub function eread01(dim eeprom_addr, offset as byte) as longint
    For offset = 0 to 3
    FSR = @ frequency + offset
    INDF = EEPROM_READ(eeprom_addr + offset)
    Next offset
    result = frequency
    delay50
end sub

' Read clock value stored in eeprom
sub function eread02(dim eeprom_addr, offset as byte) as longint
    For offset = 0 to 3
    FSR = @ xtal + offset
    INDF = EEPROM_READ(eeprom_addr + offset)
    Next offset
    result = xtal
    delay50
end sub

' Write new frequency to LCD
sub procedure lcdwrite01(dim yy as longint)
    Lcd_Cmd(LCD_CLEAR)       ' Clear display
    Lcd_Cmd(LCD_CURSOR_OFF)  ' Cursor off
    print_dec(yy,"##.######",RJZ,myvar)
    Lcd_Out(1, 4, "M1KTA")
    Lcd_Out(2,3,myvar)
    Lcd_Out(2,13,"MHz")
    delay500
end sub

' LvZ maths, calculate divisor value
sub function CalcFreq(dim f, x as longint) as longint
    dim g as float
    g = ( f / x ) * $7FFFFFFF
    result = longint(g) * 2
    delay50
end sub

' Florin Medrea's bit swap routine, forces SPI to TX LSB first
sub function swap_bits(dim data_b as byte) as byte
dim i,j as byte
  result = 0
  i = 0
  j = 7
  while i < 8
    if TestBit(data_b,i) = 1 then SetBit(result,j) end if
    inc(i)
    dec(j)
  wend
end sub

' Reset and fill DDS data register with zero values
sub procedure ddsclear
       ClearBit(PORTC,1)
       Soft_Spi_Write($00)
       Soft_Spi_Write($00)
       Soft_Spi_Write($00)
       Soft_Spi_Write($00)
       Soft_Spi_Write($00)
       SetBit(PortC,1)
end sub

' Write divisor and config values to DDS
sub procedure ddswrite(dim f as longint)      ' Soft SPI
    eread01(0, 0)                             ' Read eeprom for Freq
    delay50
    eread02(16, 0)                            ' Read eeprom for Clock
    delay50
    cfreq = CalcFreq(frequency, xtal)         ' Calculate divisor
    delay50
    TRISC = TRISC and $FD
    ClearBit(PORTC,1)                         'Sync low enable write
    byte_s = swap_bits(lo(f))                 ' Swap over and write LSB
    Soft_Spi_Write(byte_s)
    byte_s = swap_bits(hi(f))                 ' Swap over and write next byte
    Soft_Spi_Write(byte_s)
    byte_s = swap_bits(higher(f))             ' Swap over and write next byte
    Soft_Spi_Write(byte_s)
    byte_s = swap_bits(highest(f))            ' Swap over and write next byte
    Soft_Spi_Write(byte_s)
    byte_s = swap_bits($01)                   ' Swap over and write config byte
    Soft_Spi_Write(byte_s)
    SetBit(PORTC,1)                           ' Sync high disable write
    delay50
    lcdwrite01(frequency)                     ' Write new frequency to LCD
    delay50
end sub

' Write Freq value to eeprom
sub procedure ewrite(dim xx as longint)
    Eeprom_Write(0, lo(xx))
    delay50
    Eeprom_Write(1, hi(xx))
    delay50
    Eeprom_Write(2, higher(xx))
    delay50
    Eeprom_Write(3, highest(xx))
    delay50
end sub

' Write Clock value to eeprom
sub procedure ewrite2(dim xx as longint)
    Eeprom_Write(16, lo(xx))
    delay50
    Eeprom_Write(17, hi(xx))
    delay50
    Eeprom_Write(18, higher(xx))
    delay50
    Eeprom_Write(19, highest(xx))
    delay50
end sub

'Original routine from Sorcerer, read Freq from keypad
sub Procedure Frequency_Input
      Lcd_cmd(lcd_clear)
      Lcd_Out(1, 4, "Freq in MHz")
      Lcd_Out(2, 3, "Enter with #")
      Key1 = 0
      KeyInput=0
      KeyInputOld=0
    While Key1<>35                           ' Exit on #
      Key=0
      while Key = 0
      Key = Keypad_Released
      Wend
      Key1=KeyPad[Key-1]
      If Key1=42 Then                        '* = delete (last input only!)
      KeyInput=KeyInputOld
      End If
      If (Key1>47) and (Key1<58) then '0-9 are added in, anything else ignored
      KeyInputOld = KeyInput
      KeyInput = KeyInput * 10
      KeyInput = KeyInput + Key1 - 48
      End If
      print_dec(keyinput,"##.######",RJZ,myvar)
      Lcd_cmd(LCD_CURSOR_OFF)
      Lcd_Out(2, 1,"                ")
      Lcd_Out(2, 4, myvar)
      delay50
    Wend
        ewrite(Keyinput)                     ' Store frequency value in eeprom
        delay50
        ddswrite(cfreq)                      ' Two writes to set registers ???
        ddswrite(cfreq)
end sub

' Original routine from Sorcerer, read Clock from KeyPad
' Adjust for different Clock, or Fine Tune
sub Procedure Clock_Input
      Lcd_cmd(lcd_clear)
      Lcd_Out(1, 1, "Xtal Freq in MHz")
      Lcd_Out(2, 3, "Enter with #")
      Key1 = 0
      KeyInput=0
      KeyInputOld=0
    While Key1<>35                           ' Exit on #
      Key=0
      while Key = 0
      Key = Keypad_Released
      Wend
      Key1=KeyPad[Key-1]
      If Key1=42 Then                        '* = delete (last input only!)
      KeyInput=KeyInputOld
      End If
      If (Key1>47) and (Key1<58) then '0-9 are added in, anything else ignored
      KeyInputOld = KeyInput
      KeyInput = KeyInput * 10
      KeyInput = KeyInput + Key1 - 48
      End If
      print_dec(keyinput,"###.######",RJZ,myvar)
      Lcd_cmd(LCD_CURSOR_OFF)
      Lcd_Out(2, 1,"                ")      ' Cleans Line for next display
      Lcd_Out(2, 4, myvar)
      delay50
    Wend
        ewrite2(Keyinput)                   ' Store clock value in eeprom
        delay50
        ddswrite(cfreq)                     ' Two writes to set registers ???
        ddswrite(cfreq)
end sub

main:
       ADCON1 = 7
       trisa = %11111111
       trisc = 0
       Soft_Spi_Config(PortC,4, 2, 3)       ' Required for Soft_SPI
       Lcd_Init(PORTD)                      ' Init LCD on port D
       Keypad_Init(PORTB)                   ' Init KeyPad port B
       Welcome                              ' Display Welcome message
       ddsclear                             ' Write zero values to DDS buffer
       ddswrite(cfreq)                      ' Read stored values, write to DDS
       ddswrite(cfreq)                      ' Two writes to set registers ????
eloop:
       if porta.0 = 0 then                  ' Key for frequency change
       Frequency_Input                      ' Jump to frequency keypad routine
       end if
       if porta.1 = 0 then                  ' Key for Clock change
       Clock_Input                          ' Jump to clock keypad routine
       end if
goto eloop
end.