I try to program a DDS generator module AD9850.
What needs to be done is to calculate the frequency control word
F_ctrl = F_out / F_ref * 2exp32.
F_ref is 125E6 Hz and the range of F_out is from 10Hz to 40E6 Hz.
I have some noticeable differences when performing the calcs using variables in single precision.
There is improvement when I use double precision instead.
Now I want to implement frequency changes in steps of 10Hz, 100Hz, 1kHz, 10kHz, 100kHz ... 10 MHz.
If I calculate on a base of MHz, i.e. F-ref and F_out are both in MHz, I start e.g. from 1.0 MHz.
Adding a step of 100kHz (by adding 0.1 to F_out) I would expect a value for F_out of 1.1, but instead I get 1.0999999235 or something similar.
There is no ROUND function for Double and it would not help since it would round to integer values.
I tried to convert to a STRING, format the STRING with FUSING and reconvert it with VAL to a single or double format - same effect.
Also using INPUT from the terminal e.g. 0.001 is converted to something like 0.00099999 ...
But I gues also here the routine for VAL is used to convert the input into a number.
Does anybody have an idea how to overcome this problem?
Cheers,
Johannes
[b:2ddc8907e9][color=red:2ddc8907e9](BASCOM-AVR version : 2.0.7.6 )[/b:2ddc8907e9][/color:2ddc8907e9]
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