AVR Freaks

'#################### DDS_AD9850_r4a ##############################

Dim Rev As String * 2
Rev = "4a"

'Nard Awater, September 18, 2011

'Rev4: smarter circuit for DC comparator; R_dft of 10k can stay in
'Rev4a: same as 4 but continuous varying DC for the comparator

$baud = 38400
$crystal = 16000000
$regfile = "m88def.dat"

$hwstack = 40
$swstack = 10
$framesize = 10

'Uncomment next line when first programming a virgin AVR
'$prog &HFF , &HFF , &HD4 , &HF9


Wclk Alias Portb.5
Data_in Alias Portb.3
Fq_up Alias Portb.0
Ad9850_reset Alias Portb.1


'setup i/o
Ddrb = &B00101111
Ddrc = &B00111111
Ddrd = &B11111110

Config Spi = Hard , Interrupt = Off , Data Order = Lsb , Master = Yes , Polarity = Low , Phase = 0 , Clockrate = 16 , Noss = 1 , Spiin = 0
Spiinit

Const Clk_in = 125000000                                    'that's the DDS-clock
Const Braincells = &H100000000                              'wishfull thinking ??   &H100000000 = 2^32

Print "AD9850 on Freeduino rev " ; Rev
'The AD9850 needs to be reset since it's using the same interface as ISP programming
Print "Resetting AD9850 ... ";
Waitms 100
Set Ad9850_reset
Waitms 100
Reset Ad9850_reset
Print "done !"

'serial mode
'Freq0 first, freq31 last
'Send 4 bytes in SPI to push all bits of this Long out ....
Dim Freq_accu As Long
' ... followed by
Dim Phase_cntrl As Byte
'make sure that Phase_cntrl.1 and Phase_cntrl.0 are always 0 ; other combinations are for factory testing only
Phase_cntrl = 0
Power_down Alias Phase_cntrl.2
'Phase_cntrl.7 through Phase_cntrl.3 set the phase of the signal

'mode2  CTC OCR0A=top OC0A toggles on compare
Tccr0a = &B01000010
Ocr0a = 100

Tccr0b = &B00000001

Dim Rate As Byte


'###############################################################
'Some math:

'F_out = (Freq_accu x 125x10^6) / 2^32    'from the datasheet
' .... so
'Freq_accu = (F_out x 2^32) / 125 x 10^6
'###############################################################


Dim Freq_accu_f As Single
Dim F_out As Single

Input "Freq = " , F_out
Freq_accu_f = F_out * Braincells
Freq_accu_f = Freq_accu_f / Clk_in
Freq_accu = Freq_accu_f


Do

   Spiout Freq_accu , 4                                     '4 bytes, LS Bit first
   Spiout Phase_cntrl , 1

   Waitus 100                                               'no flag is checked so wait a while for SPI to finish

   'and effectuate
   Set Fq_up
   Reset Fq_up


   Rate = Rate + 5
   If Rate > 250 Then Rate = 5

   Ocr0a = Rate

   Waitms 40

Loop


End