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Old October 17th 03, 06:20 AM
Tim
 
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Default AD9850 DDS - Help prevent suicide

No, I'm tasting gun metal yet but if you are experienced with the AD9850 DDS
please read on.

I am clocking out 40 bits serially to the unit, data word + control, for
some reason the DDS only updates the output freq based on the results of the
first 16 bits. When powered up the unit is stable, not misbehaving and seems
to respond with the exception of the last 16 bit freq bits. If the last 16
bits are set to 0 the output results are the same as when they are vaild.
It jumps about 600 hz or so instead of 10 hz

What has be scratching my head is that it must be "seeing" the last 16 bits
and control word or it wouldn't come alive. Has anyone any input on what may
be missing, similar problems? I clock out 32 bit freq control, then 8 bit
control word then a 10us wide F_update pulse. Again, stable, working but
ignoring last 16 bits.

Using a PIC 16F73 and simultaneously dumping the 4, 8 bit words out the
serial port I get:

Changing freq starting with 7.10000 by 10 hz

freq 7.10001 %00101101%01110000%10101000%00001000
freq 7.10002 %00101101%01110000%10101100%00111010
freq 7.10003 %00101101%01110000%10110000%01101100
freq 7.10004 %00101101%01110000%10110100%10011101
freq 7.10005 %00101101%01110000%10111000%11001111
freq 7.10006 %00101101%01110000%10111101%00000001
freq 7.10007 %00101101%01110000%11000001%00110011
freq 7.10008 %00101101%01110000%11000101%01100100
freq 7.10009 %00101101%01110000%11001001%10010110
freq 7.10010 %00101101%01110000%11001101%11001000
freq 7.10011 %00101101%01110000%11010001%11111010
freq 7.10012 %00101101%01110000%11010110%00101011
freq 7.10013 %00101101%01110000%11011010%01011101
freq 7.10014 %00101101%01110000%11011110%10001111
freq 7.10015 %00101101%01110000%11100010%11000001
freq 7.10016 %00101101%01110000%11100110%11110010
freq 7.10017 %00101101%01110000%11101011%00100100
freq 7.10018 %00101101%01110000%11101111%01010110
freq 7.10019 %00101101%01110000%11110011%10001000
freq 7.10020 %00101101%01110000%11110111%10111001
freq 7.10021 %00101101%01110000%11111011%11101011
freq 7.10022 %00101101%01110001%00000000%00011101 - audible change heard
here and again when bit 16 rollsover to 0 again
freq 7.10023 %00101101%01110001%00000100%01001111
freq 7.10024 %00101101%01110001%00001000%10000000
freq 7.10025 %00101101%01110001%00001100%10110010
freq 7.10026 %00101101%01110001%00010000%11100100
freq 7.10027 %00101101%01110001%00010101%00010110
freq 7.10028 %00101101%01110001%00011001%01000111
freq 7.10029 %00101101%01110001%00011101%01111001
freq 7.10030 %00101101%01110001%00100001%10101011
freq 7.10031 %00101101%01110001%00100101%11011100
freq 7.10032 %00101101%01110001%00101010%00001110
freq 7.10033 %00101101%01110001%00101110%01000000
freq 7.10034 %00101101%01110001%00110010%01110010
freq 7.10035 %00101101%01110001%00110110%10100011
freq 7.10036 %00101101%01110001%00111010%11010101
freq 7.10037 %00101101%01110001%00111111%00000111
freq 7.10038 %00101101%01110001%01000011%00111001
freq 7.10039 %00101101%01110001%01000111%01101010
freq 7.10040 %00101101%01110001%01001011%10011100
freq 7.10041 %00101101%01110001%01001111%11001110
freq 7.10042 %00101101%01110001%01010100%00000000
freq 7.10043 %00101101%01110001%01011000%00110001
freq 7.10044 %00101101%01110001%01011100%01100011
freq 7.10045 %00101101%01110001%01100000%10010101
freq 7.10046 %00101101%01110001%01100100%11000111
freq 7.10047 %00101101%01110001%01101000%11111000
freq 7.10048 %00101101%01110001%01101101%00101010
freq 7.10049 %00101101%01110001%01110001%01011100
freq 7.10050 %00101101%01110001%01110101%10001110
freq 7.10051 %00101101%01110001%01111001%10111111
freq 7.10052 %00101101%01110001%01111101%11110001
freq 7.10053 %00101101%01110001%10000010%00100011
freq 7.10054 %00101101%01110001%10000110%01010101
freq 7.10055 %00101101%01110001%10001010%10000110
freq 7.10056 %00101101%01110001%10001110%10111000
freq 7.10057 %00101101%01110001%10010010%11101010
freq 7.10058 %00101101%01110001%10010111%00011100
freq 7.10059 %00101101%01110001%10011011%01001101
freq 7.10060 %00101101%01110001%10011111%01111111
freq 7.10061 %00101101%01110001%10100011%10110001
freq 7.10062 %00101101%01110001%10100111%11100010
freq 7.10063 %00101101%01110001%10101100%00010100
freq 7.10064 %00101101%01110001%10110000%01000110
freq 7.10065 %00101101%01110001%10110100%01111000
freq 7.10066 %00101101%01110001%10111000%10101001
freq 7.10067 %00101101%01110001%10111100%11011011
freq 7.10068 %00101101%01110001%11000001%00001101
freq 7.10069 %00101101%01110001%11000101%00111111
freq 7.10070 %00101101%01110001%11001001%01110000
freq 7.10071 %00101101%01110001%11001101%10100010
freq 7.10072 %00101101%01110001%11010001%11010100
freq 7.10073 %00101101%01110001%11010110%00000110
freq 7.10074 %00101101%01110001%11011010%00110111
freq 7.10075 %00101101%01110001%11011110%01101001
freq 7.10076 %00101101%01110001%11100010%10011011
freq 7.10077 %00101101%01110001%11100110%11001101
freq 7.10078 %00101101%01110001%11101010%11111110
freq 7.10079 %00101101%01110001%11101111%00110000
freq 7.10080 %00101101%01110001%11110011%01100010
freq 7.10081 %00101101%01110001%11110111%10010100
freq 7.10082 %00101101%01110001%11111011%11000101
freq 7.10083 %00101101%01110001%11111111%11110111
freq 7.10084 %00101101%01110010%00000100%00101001 - again audible change in
rx
freq 7.10085 %00101101%01110010%00001000%01011011
freq 7.10086 %00101101%01110010%00001100%10001100
freq 7.10087 %00101101%01110010%00010000%10111110
freq 7.10088 %00101101%01110010%00010100%11110000


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AD9850 DDS - Help prevent suicide Tim Homebrew 6 October 23rd 03 03:31 AM


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