AVR DDS?

techknight · Joined: 21 Apr 2008 Posts: 231

I am working on a project where I need a digitally controlled adjustable frequency between roughly 50khz and 1mhz. But the catch here is I need a full output triangle wave.

I was doing some research, and it appears i need a DDS setup. and maybe the AD9833, everything I am finding on the web is pointing me into that direction.

Has anyone written a library/driver for this chip in BASCOM? Just wondering.

I see some test code laying around the web, but most of it is in foreign language and isnt translating well. And the rest is in C, but I dont program in C.

pippofranco · Joined: 02 Oct 2010 Posts: 6

techknight · Joined: 21 Apr 2008 Posts: 231

I would use the 9850 which is what everyone else is using, but it has no support for Triangle, which is required.

n7qwt · Joined: 21 Dec 2006 Posts: 2

My code for programming an AD9833 for sine wave output.

Garrett B. Waltrip
N7QWT

'Start Hardware Configuration
'#######################################################################

$regfile = "8515def.dat"
$crystal = 8000000

Config Pind.3 = Output 'Fsync
Config Pind.4 = Output 'Sclk
Config Pind.5 = Output 'SData

Fsync Alias Portd.3
Sclk Alias Portd.4
Sdata Alias Portd.5

Set Sclk 'Set initial pin state
Set Fsync 'Set initial pin state

'#######################################################################
'End Hardware Configuration

Dim Count As Double
Dim Freq As Double
Dim Setfreq As Long At &H90
Dim Low_byte0 As Word At &H90 Overlay
Dim High_byte0 As Word At &H92 Overlay

'############################################################################################################
'############################################################################################################

Freq = 400 'Change this value to the required Freq. in Hertz

'############################################################################################################
'############################################################################################################

Count = .093132257 'This is based on a 25 MHz Osc driving the 9833.
Freq = Freq / Count
Setfreq = Freq
Shift Setfreq , Left , 2 'The shifts take care of converting from a 16 bit word to a 14 bit.
Shift Low_byte0 , Right , 2
Setfreq = Setfreq + &H40004000

'Declare subroutines
'#######################################################################

Declare Sub Send_dds(byval Sw As Word)

'#######################################################################
'End Declare subroutines

'Start sending commands to the DDS
'#######################################################################

Call Send_dds(&H2100) 'Change this for triangle wave to the appropriate command.

Call Send_dds(low_byte0)

Call Send_dds(high_byte0)

Call Send_dds(&H2000) 'Change this for triangle wave to the appropriate command.

'#######################################################################
'End sending commands to the DDS

Powerdown 'Put CPU in Powerdown state for less noise
End 'End program

'########################################################################

'This is the subroutine that send the data to the DDS
'########################################################################
Sub Send_dds(byval Sw As Word)

Reset Fsync
Waitms 1
Shiftout Sdata , Sclk , Sw , 0 , 16 , 500
Waitms 1
Set Fsync

End Sub

'########################################################################